Banksia, Leucadendron, Leucospermum, and - Acta Horticulturae

Banksia, 

Leucadendron, 

Leucospermum 

and Protea 

A publication of the 

International Society for Horticultural Science 

and the International Protea Association 

Scripta Horticulturae 

Number 5 

Ornamentals

International Society for Horticultural Science 

Société Internationale de la Science Horticole 

® is a publication of ISHS. 

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Proteaceous Ornamentals: 

Banksia, Leucadendron, Leucospermum, and Protea. 

Reprinted with permission of John Wiley & Sons, Inc., 

from Horticultural Reviews © , edited by Jules Janick

ISSN 1813 - 9205 

ISBN 978 90 6605 446 2, Scripta Horticulturae Number 5 

Published by ISHS, June 2007 

Executive Director of ISHS: Ir. J. Van Assche 

ISHS Secretariat, PO Box 500, 3001 Leuven 1, Belgium 

Printed by Drukkerij Geers, Eeckhoutdriesstraat 67, 9041 Gent-Oostakker, Belgium 

© 2007 by the International Society for Horticultural Science (ISHS). All rights reserved. 

No part of this book may be reproduced and/or published in any form or by any means, 

electronic or mechanical, including photocopying, microfilm and recording, or by any 

information storage and retrieval system, without written permission from the publishers. 

Photograph on the front cover: 

1. Leucospermum ‘Caroline’ 

2. Protea ‘Pink Ice’ 

3. Leucadendron ‘Safari Sunset’ 

By courtesy of 

Eric Hunt 

www.orchidphotos.org 

Plate I: Celia Rosser 

Banksia Serrata (Saw Banksia) 1972, watercolour and pencil on paper, 55.8 x 76.2 cm 

Collection of the artist, Image courtesy of Monash University Museum of Art 

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TABLE OF CONTENTS 

Article 1: Banksia: New Proteaceous Cut Flower Crop 9 

by Margaret Sedgley 

I. INTRODUCTION 10 

II. TAXONOMY 11 

III. BREEDING SYSTEMS 12 

A. Reproductive Structure 12 

B. Breeding Biology 14 

C. Genetic Variability 15 

IV. PLANT IMPROVEMENT 15 

A. Controlled Pollination 15 

B. Selection 16 

C. Interspecific Compatibility 16 

D. Cultivars 18 

V. PHYSIOLOGY 18 

A. Flowering 18 

B. Propagation 19 

C. Water and Nutrient Uptake 20 

D. Postharvest Physiology 21 

VI. PRODUCTION 21 

A. Culture 21 

B. Diseases and Pests 22 

VII. CONCLUSIONS 23 

LITERATURE CITED 23 

Article 2: Leucospermum: Botany and Horticulture 27 

by Richard A. Criley 


II. BOTANY 31 

A. Origin and Ecology 31 

B. Morphology 31 

C. Taxonomy 32 

D. Floral Physiology 34 

1. Flowering 34 

2. Pollination Biology 36 

E. Genetics 37 

III. HORTICULTURE 38 

A. Propagation 38 

1. Seed 38 

2. Cuttage 39 

3. Grafting 41 

4. Tissue Culture 42 

B. Environmental Responses 44 

1. Light 44 

2. Temperature 44 

3. Cold Tolerance 45 

4. Soils 45 

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C. Cultural Practices 46 

1. Spacing 46 

2. Pruning 46 

3. Disbudding 47 

4. Irrigation 50 

5. Nutrition and Fertilization 50 

6. Production Period 52 

7. Growth Regulator Studies 53 

D. Plant Protection 55 

1. Diseases 55 

2. Nematodes 56 

3. Insect Pests 56 

4. Weeds 56 

E. Postharvest Studies 57 

1. Handling and Storage 57 

2. Insect Eradication 57 

3. Grades and Standards 58 

F. Genetic Improvement 59 

G. Leucospermum as a Pot Plant 60 

1. Production 60 

2. Postproduction 63 

IV. CROP POTENTIAL AND RESEARCH NEEDS 63 


Article 3: Protea: A Floricultural Crop from the Cape Floristic Kingdom 77 

by J.H. Coetzee and G.M. Littlejohn 


II. HISTORY 80 

A. Taxonomy and Cultivation 80 

B. Research 82 

C. World Industry 83 

III. REPRODUCTIVE BIOLOGY 84 

IV. CROP IMPROVEMENT 86 

A. Genetic Variability 86 

B. Selection 88 

C. Hybridization 89 

D. Interspecific Hybridization 90 

E. Cultivars 91 

V. PHYSIOLOGY 92 

A. Flowering 92 


1. Sexual Reproduction 94 

2. Vegetative Propagation 94 



C. Water and Nutrient Uptake 95 

D. Postharvest Physiology 96 

VI. PRODUCTION 97 

A. Cultivation 97 

B. Pathogens Associated with Diseases of Protea 98 

1. Pathogens of Roots 99 

2. Pathogens of Leaves 100 

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3. Pathogens of Shoots, Stems, and Inflorescences 101 

4. Pathogens of Woody Stems 102 

C. Phytophagous Insects Fauna of Protea 102 

1. Flower Visitors 102 

2. Borers 102 

3. Folivorous Insects 103 

4. Sap Suckers 103 

VII. CONCLUSION 104 


Article 4: Leucadendron: A Major Proteaceous Floricultural Crop 113 

by Jaacov Ben-Jaacov and Avner Silber 


II. BOTANY OF THE GENUS LEUCADENDRON 114 

A. Taxonomy 114 

B. Distribution and Ecology 115 

III. WORLD INDUSTRY AND ECONOMICS 117 

A. Types of Leucadendron Cut Branches 118 

B. Yield 119 

IV. HORTICULTURE 119 

A. Genetic Improvement 119 


1. Seeds 124 

2. Cuttings 126 



C. Site Selection and Environmental Responses 129 

D. Cultural Practices 131 

1. Specific Requirements of Species and Cultivars 131 

2. Spacing 131 

3. Nutrition of Leucadendron 131 

4. Response of L. ‘Safari Sunset’ to Irrigation Regime 136 

5. Overcoming Soil Problems in Cultivating L. ‘Safari Sunset’ in Israel 137 

6. Control of Growth and Flowering—Pruning and Pinching 141 

E. Plant Protection 141 

1. Diseases 141 

2. Physiological Disorders 144 

3. Insects 144 

4. Nematodes 144 

5. Weeds 145 

F. Post Harvest Studies 145 

1. Handling and Storage 145 

2. Insect Eradication 146 

G. Leucadendron as a Pot Plant 146 

V. CROP POTENTIAL AND RESEARCH NEEDS 147 


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PREFACE 

by Richard A. Criley, University of Hawaii 

More than 1400 species have been recognized in the ancient Proteaceae family 

(Rebelo 1995). Their occurrence is mostly distributed between Australia with about 800 

species and Africa with about 400 species with the remainder found in South America, 

the islands east of New Guinea, and a few species in southeast Asia, New Zealand, and 

Madagascar. They are broadly referred to as proteas, although we identify specific genera 

by their Latin names. The subfamily Proteoideae, largely found in Africa, has contributed 

the genera Protea, Leucadendron, and Leucospermum to floricultural trade, while the 

Australian Grevilleoideae has contributed Banksia and Grevillea that have found similar 

use in floriculture and landscaping. Other genera are still emerging in importance (Criley, 

2001). Registration of proteaceous ornamentals by the International Protea Register is 

web-based: http://www.nda.agric.za/docs/Protea2002/proteaceae_register.htm. 

Recognizing the importance of these plants, Dr. Jules Janick, editor of the 

Horticultural Reviews series, enlisted a number of authors to prepare reviews of four 

genera: Dr. Margaret Sedgley (1998) to cover Banksia, Dr. Richard Criley (1998) to 

cover Leucospermum, Drs. J. H. Coetzee and Gail Littlejohn (2001) to cover Protea and 

Drs. Jaacov Ben-Jaacov and Avner Silber (2006) to cover Leucadendron. Since the 

literature about these plants is quite diverse and some is published in less-than-widelyread 

languages such as Afrikans and Hebrew, these authors have brought to the fore 

syntheses of the taxonomy, culture, breeding, propagation, nutrition, disease and insect 

pests, and postharvest practices that would otherwise remain out of the grasp of most 

readers. Obviously, some of the information on economics and areas of production were 

out-dated at the time of this re-publication, and additional research has been published. 

Although these reviews summarize many sources of literature for these 

ornamentals, the Protea Working Group of the International Society for Horticultural 

Science also has generated significant information from seven symposia and one 

workshop on proteas, with papers published in the Acta Horticulturae series.(listed 

below).Moreover, students of Professor Gerard Jacobs of the University of Stellebosch in 

South Africa have published theses that have added significantly to our knowledge of 

physiology and management of the South African Protea and Leucospermum, while Dr. 

Sedgley’s students at the University of Adelaide have contributed to our knowledge of 

Banksia. Research has been conducted in many of the Mediterranean climates in which 

proteas survive and thrive, most notably South Africa, Zimbabwe, Israel, New Zealand, 

Australia, southern California, Hawaii, the Canary Islands, Portugal, and France, but the 

search for “new” floral crops has lead to evaluations in Chile, Costa Rica, Thailand, and 

interest in other parts of the world has grown as well. 

Through the joint efforts of the International Protea Association and the 

International Society for Horticultural Science, it has been possible to gather together the 

reviews on Banksia, Leucadendron, Leucospermum, and Protea into this volume of 

Scripta Horticulturae. We thank the publishers of Horticultural Reviews, John Wiley & 

Sons, Inc., for permission to bring these valuable sources together into one book. May 

this volume stimulate additional research and understanding of these fascinating plants! 

7

Bibliography 

Acta Horticulturae and Workshops on the Proteaceae 

Ben-Jaacov, J and D.J. Ferreira (Eds.) 1985. First International Protea Research 

Symposium. Acta Horticulturae185. 

Ben-Jaacov, J. and A. Silber. 2006. Leucadendron: A major proteaceous floricultural 

crop. HorticulturaeRev. 32:167-228. 

Brits, G.J. and J. T. Meynhardt. (Eds.) 1992. International Workshop on Intensive 

Cultivation of Protea. Acta Horticulturae316. 

Brits, G.J. and M.G. Wright. (Eds.) 1995. Third International Protea Research 


Coetzee, J. H. and G. M. Littlejohn. 2001. Protea: A floricultural crop from the Cape 

Floristic kingdom. Hort. Rev. 26:1-48. 

Criley, R. A. 1998. Leucospermum: Botany and horticulture. Hort. Rev. 22:27-90. 

Criley, R. A. 2001. Proteaceae; Beyond the big three. Acta Horticulturae545:79-85. 

Criley, R.A. (Ed.) 1990. Second International Protea Research Symposium, Acta 

Horticulturae264. 

Criley, R.A. (Ed.) 2001. Proceedings of the Fifth International Protea Research 


Gerber, A. I. and K. W. Leonhardt. 2006. (Eds.) 2006. Proceedings of the 7th 

International Protea Research Symposium. Acta Horticulturae716. 

Leonhardt, K.W. (ed.) 2003. Proceedings of the Sixth International Protea Research 


Littlejohn, G.M. and H. Hettasch. (Eds.) 1997. Proceedings of the Fourth International 

Protea Working Group Symposium. Acta Horticulturae453. 

Rebelo, T. 1995. SASOL Proteas: a field guide to the proteas of Southern Africa. 

Fernwood Press. Vlaeberg, S. Africa. 

Sedgley, M. 1998. Banksia: New proteaceous cut flower crop. Hort. Rev. 22:1-25 

8

Banksia: New Proteaceous Cut 

Flower Crop ∗ 

Horticultural Reviews, Volume 22, Edited 

by Jules Janick 

ISBN 0-471-25444-4 0 John Wiley & 

Sons, Inc. 

by: Margaret Sedgley 

∗ Research conducted by M. Sedgley was supported by the Australian Research Council, 

the Rural Industries Research and Development Corporation, the Horticultural Research 

and Development Corporation, the Australian Flora Foundation, the Society for Growing 

Australian Native Plants New South Wales, and the International Protea Association. 

Thanks to Michelle Wirthensohn, and Meredith Wallwork for the photographs. 

1 

9

I. INTRODUCTION 

Banksia species (Plate I) have been cultivated for the international cut flower 

market for only 20 to 30 years, but there is increasing interest in areas other than the 

native home, Australia, with production in Israel, South Africa, Hawaii, and California 

(Ben-Jaacov 1986; Sedgley 1996). Within Australia, Banksia is one of the four most 

widely planted commercial native genera, but production is based on seedling material 

and between plant variability is high. Banksia species for the fresh cut flower market must 

fulfill strict commercial criteria, which include terminal blooms and long stem length 

(Fig. 1.1), and further research is needed into all aspects of Banksia biology and 

production. In addition to the fresh cut flower market, Banksia stems are traded as dried 

and dyed blooms, and a wide range of species is used in environmental horticulture, for 

the attractive inflorescences and foliage, and to attract birds and other wildlife. Although 

there has been little work conducted so far on the use of banksias as pot plants, recent 

developments with related genera suggest that such an approach may be productive (Ben- 

Jaacov et al. 1989). Banksia wood and cones are turned or incorporated into ornaments, 

and the timber of some species has been used for furniture. 

Fig. 1.1. Inflorescence of Banksia 'Waite crismon', shown together with other flowers. 

Other genera from the Proteaceae that are important horticulturally include the 

Australian Grevillea, Dryandra, Isopogon, Telopea, and Macadamia, and the South 

African Protea, Leucadendron, Leucospermum, and Serruria. Horticultural aspects of 

Banksia production have been reviewed by Sedgley (1996), and recent research reviews 

on related genera include leaf blackening in cut Protea flowers (Jones et al. 1995), while 

Leucospermum will be covered by Criley in this volume. The objective of the present 

paper is to review research activity that underpins the current development of Banksia as 

a floricultural crop. 

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II. TAXONOMY 

The Banksia genus includes 76 taxa, which are currently grouped into two 

subgenera, three sections, and 13 series (Table 1.1) (George 1981, 1988, 1996, 1997; 

Maguire et al. 1996). The most widely cultivated species for floriculture belong to the 

subgenus Banksia sections Banksia and Coccinea, and are characterized by terminal 

flowering of large showy inflorescences. These include the scarlet Banksia, B. coccinea, 

the pink B. menziesii (Fig. 1.2), the green/yellow B. Baxteri and B. speciosa, and the 

orange species B. ashbyi, B. prionotes, B. hookeriana, B. burdettii, and B. victoriae. B. 

ashbyi is mainly cultivated in Israel, whereas the others are grown in most Banksia 

production areas. Others cultivated to a lesser extent for cut flowers or foliage include the 

yellow-flowered species B. grandis, B. sceptrum, and B. integrifolia, the brown B. 

solandri and B. brownii, and the orange B. ericifolia. Many other species of Banksia 

produce axillary blooms that are obscured by foliage and have short stems, but some 

terminal flowering forms of otherwise axillary-bearing species, such as the red B. 

occidentalis, have recently been identified and used for cut flower production. 

The most important commercial species is B. coccinea, and this is also the most 

problematic taxonomically. It has a number of unique features, and no obvious close 

relatives in the genus. A recent cladistic analysis of the genus failed to clarify its status 

(Thiele and Ladiges 1996), and it is hoped that molecular systematics will provide the 

answer (Maguire et al. 1997d; Mast 1997). It is important to know the taxonomic 

affinities of the major commercial species, so that attempts at interspecific hybridization 

can be directed toward the most closely related and hence productive crosses. 

Table 1.1. Systematic sequence in Banksia (after George 1997). 

Subgenus Banksia 

Section Banksia 

Series Salicinae: B. dentata L.f., B. aquilonia A.S. George, *B. integrifolia L.f., B. 

plagiocarpo A.S. George, B. oblongifolia Cav., B. robur Cavanilles, B. conferta A.S. 

George, *B. paludosa R.Br., *B. marginata Cav., B. canei J.H. Willis, B. saxicola A.S. 

George. 

Series Grandes: *B. grandis Willd., B. solandri R.Br. 

Series Banksia: B. serrata L.f., B. aemula R.Br., *B. ornata F. Muell. ex Meissn.,*B. 

bmrteri R.Br., *B. speciosa R.Br., *B. menziesii R.Br., *B. candolleana 

Meissn., B. sceptrum Meissn. 

Series Crocinae: *B. prionotes Lindley, *B. burdettii E.G. Baker, *B. hookeriana Meissn., 

B. victoriae Meissn. 

Series Prostratae: B. goodii R.Br., *B. gardneri A.S. George, B. chamaephyton A,S. 

George, *B. blechnifolia F. Muell., *B. repens Labill., *B. petiolaris F. Muell. 

Series Cyrtostylis: *B. media R.Br., *B. pmemorsa Andrews, B. epica A.S. George, B. 

pilostylis C. Gardner, *B. attenuata R.Br., *B. ashbyi E.G. Baker, B. benthamiana C. 

Gardner, B. audax C. Gardner, B. lullfitzii C. Gardner, *B. elderiana F. Muell & Tate, 

*B. laevigata Meissn., B. elegans Meissn., B. lindleyana Meissn. 

Series Tetragonae: *B. lemanniana Meissn., B. caleyi R.Br., B. aculeata A.S. George. 

Series Bauerinae: *B. baueri R.Br. 

Series Quercinae: *B. quercifolia R.Br., B. oreophila A.S. George. 

Section Coccinea: *B. coccinea R.Br. 

Section Oncostylis 

Series Spicigerae: B. spinulosa A.S. George, *B. ericifolia L.f., B. verticillata R.Br., B. 

seminuda (A.S. George) B. Rye, B. littoralis R.Br., *B. occidentalis R.Br., *B. brownii 

Baxter ex R.Br. 

Series Tricuspidae: *B. tricuspis Meissn. 

Series Dryandroideae: B. dryandoides Baxter ex Sweet. 

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Series Abietinae: *B. sphaerocarpa R.Br., *B. micrantha A.S. George, B. grossa 

A.S.George, *B. telmatiaea A.S. George, B. leptophylla A.S. George, B. lanata A.S. 

George, B. scabrella A.S. George, B. violacea C. Gardner, B. incana A.S. George, *B. 

laricina C. Gardner, *B. pulchella R.Br., B. meisneri Lehmann, *B. nutans R.Br. 

Subgenus Isostylis: B. ilicifolia R.Br., B. oligantha A.S. George, *B. cuneata A.S. George. 

*Species tested for interspecific compatibility. 

Fig. 1.2. Inflorescence and foliage of Banksia menziesii. 

III. BREEDING SYSTEMS 

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A. Reproductive Structure 

Banksia species range from prostrate forms to trees, and all are evergreen woody 

perennials (Fig. 1.3), some of which regenerate from lignotubers following fire. Many 

flowers are crowded into showy inflorescences, which are followed by infructescences, 

often called cones, in which relatively few seeds develop in large woody follicles. The 

most common flower colors are yellow, orange, green, brown, and red. Banksia violacea 

produces purple flowers, and although the blooms are too small and obscured by foliage 

to be used in floriculture, it may provide a useful character for plant breeding. Foliage 

may be fine and needle-like or coarsely serrated. Banksia floral structure conforms to the 

typical proteaceous pattern of large numbers of individual flowers grouped together to 

form conspicuous inflorescences (Fig. 1.2). In B. coccinea and B. menziesii, the flowers 

are produced spirally on the inflorescence, with 13 separate genetic spirals initiating 

simultaneously (Fuss and Sedgley 1990). The flowers develop in pairs, with each flower 

subtended by a floral bract and the pair of florets and their floral bracts subtended by a 

common bract. These bracts are inconspicuous, and the floral display is provided by the 

colored perianths and styles.

Fig. 1.3. Tree of Banksia baxteri. 

Each Banksia flower has four tepals, with a single bilobed anther attached by a 

short filament to the distal region of the perianth. The pistil consists of an ovary with two 

ovules, and a long style with a small pollen-receptive stigmatic area in the apical region. 

In some species, the style elongates more quickly than the perianth during floral 

development, and arches beyond the corolla tube by protruding between two perianth 

members. An unusual feature of the genus is that the Banksia floral display is contributed 

entirely by the perianth and the style. In B. coccinea, for example, the inflorescence is 

gray prior to anthesis from the gray color of the perianths, and red following anthesis from 

the red color of the styles. 

The distal portion of the Banksia style is specialised for pollen presentation, and 

its structure varies between species (Fig. 1.4) (Sedgley et a1.1993). The receptive stigmatic 

cells are located in a groove toward the tip of the pollen presenter, which in most species 

is located longitudinally and obliquely terminal, although in a few it is transverse or 

lateral. In B. menziesii, the pollen presenter has a complex internal structure, as observed 

by light microscopy, with the transmitting tissue enclosed by transfer cells, which may 

serve to maximize water and nutrient supply to the growing pollen tubes (Clifford and 

Sedgley 1993). The transfer cells are not present in the rest of the style, and the 

number of transmitting tissue cells declines over the approximately 2 cm length of the 

style, with only 11 cells present at the junction with the ovary. The Banksia style is a 

robust wiry structure with lignified sclerenchyma tissue located in the outer cortex. After 

flowering, the inflorescence develops into a woody infructescence, and successfully 

fertilised ovaries develop into follicles, each with one or two seeds. In most species the 

infructescence does not increase in size after flowering, and the mature follicles are much 

larger than the ovaries at anthesis, resulting in spatial limitations to fertility (Fuss and 

Sedgley 1991a,b). An exception is B. grandis in which the axis, common bracts, and 

floral bracts enlarge around the follicles and become lignified, such that the mature 

infructescence can be used for cutting and turning into craft objects. Most species do not 

release their seeds until after fire (Zammit and Westoby 1987). 

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14 

B. Breeding Biology 

As in many other proteaceous genera, the flower of Banksia exhibits protandry, 

with the anthers dehiscing prior to flower opening to deposit their pollen on the pollen 

presenter (Sedgley and Fuss 1995). This generally occurs about one day before the 

flower opens, and following anthesis the pollen is collected by foraging fauna. At 

this stage the stigma papilla cells are not receptive to pollen, and peak stigma 

receptivity is attained three days after flower opening. This has been determined by 

increase in the width of the stigmatic groove and by increase in pollen germination on 

the stigma in B. menziesii (Fuss and Sedgley 1991a), and in B. coccinea by increase in 

stigmatic secretion (Fuss and Sedgley 1991b). In the natural habitat all of the flower's own 

pollen has been removed by insect, bird, or mammal pollinators by the time the stigma 

is receptive, and the flower may be cross pollinated by a foraging animal that has visited 

another plant. 

(b) 

Fig. 1.4. Pollen presenter of (a) Banksia serrata and (b) Banksia grandis. Bar represents 1 

mm. 

Outcrossing is a feature of the genus (Carthew et al. 1988; Sedgley 1995d; 

Goldingay and Carthew 1997), and most species of Banksia that have been studied produce 

less seed following self pollination than following cross pollination. The self 

(a)

incompatibility is only partial, however, as controlled hand pollination of B. menziesii 

resulted in 80% infructescence set following crossing compared with 33% following 

selfing, and 6 follicles per crossed inflorescence compared with 1.3 after selfing (Fuss and 

Sedgley 1991c). In B. coccinea all pollinated inflorescences set some seed, but the 

crossed infructescences had 40.7 seeds compared with 27.9 after selfing (Fuss and 

Sedgley 1991b,c). Further information was obtained from a 5 by 5 diallel 

experiment, with the results measured by pollen tube growth, observed using 

fluorescence microscopy (Fuss and Sedgley 1991b). Pollen tubes had reached the base of 

the style by six days after pollination, but self pollination generally resulted in poorer tube 

growth. Statistical analysis showed that some plants were more successful parents than 

others, that some genotype combinations were better than others, and that some crosses 

were more fertile when conducted in one direction than in the other. These results 

indicate that Banksia has a mixed mating system with complex genetic interactions. 

Most species are characterised by relatively low seed yields (Ayre and Whelan 1989), 

and this has been attributed to a wide range of possible causes, including breeding 

system constraints, pollinator limitation, insect and bird predation, and poor nutrition. 

C. Genetic Variability 

Outcrossing plants generally show high levels of morphological variability, and 

this is true of the Banksia genus. For example, there are four distinct geographically 

isolated forms of B. canei reported (Salkin and Hallam 1978). More subtle variation is 

found in most species, including variability in yield, bloom quality and color, time of 

flowering, and disease tolerance (Fuss and Sedgley 1991a; Sedgley 1995c,d). 

In addition to morphological characters, biochemical methods are increasingly 

used to measure genetic variation. Isozyme analysis has demonstrated high levels of 

genetic diversity in B. attenuata, B. menziesii (Scott 1980), and B. cuneata (Coates and 

Sokolowski 1992), and this has been confirmed in the latter species using RAPD-PCR 

analysis (Maguire and Sedgley 1997c). A further application of RAPD-PCR is to 

compare plants in wild populations with those in cultivation. This approach has 

demonstrated that for B. coccinea, variability is lower between cultivated than between 

natural populations, indicating that the cultivated populations studied are closely 

related to each other and suggesting that the germplasm in cultivation may not represent 

the full variability available in the wild (M. A. Rieger and M. Sedgley unpublished). 

This is not the case for B. menziesii, which appears to be well-represented in 

cultivation. Using RAPD-PCR, it is also possible to identify which natural and 

cultivated populations are the most closely related, so that wild populations that are 

already represented in cultivation do not need to be sampled further. 

IV. PLANT IMPROVEMENT 

Variability is a disadvantage to the grower because it leads to inconsistency in 

product, but it means that there is ample scope for selection and breeding of new improved 

cultivars. For Banksia the method of preserving desirable characteristics is single plant 

selection followed by vegetative propagation. The population subjected to selection 

may be wild populations in the native habitat, open pollinated populations under 

cultivation, or cultivated populations derived from controlled pollination. 

A. Controlled Pollination 

Research into the Banksia breeding system has been used to develop controlled 

hand pollination methods (Fuss and Sedgley 1991c). Inflorescences of the seed parent 

are covered with a bag to exclude pollinating fauna, after the removal of all open flowers. 

One day later, the bag is opened, pollen is removed from all newly-opened flowers 

15

using a looped synthetic pipe-cleaner, all unopened flowers are removed, and the bag is 

replaced. Three days later, at peak receptivity of the stigma, pollen is transferred to the 

stigma, using the pollen-laden pollen presenter from the pollen parent as a paint brush to 

insert the pollen into the stigmatic groove. The bag is replaced for a few days, to prevent 

any further pollen transfer, after which it is removed during the remainder of the seed 

development period, which varies with species from five to sixteen months (Sedgley et al. 

1994). Seed set following controlled hand pollination is around 3.5% (Sedgley et al. 1996), 

and mature seed are collected and germinated for subsequent selection. 

Pollen storage and viability testing are important adjuncts to a breeding program. 

B. menziesii pollen was stored at 20, 4, -20, -80, and -196°C, and assessed using 

a semi-solid medium of 1% agar, 15% sucrose, 0.01% boric acid, 0.03% calcium nitrate, 

0.02% magnesium sulphate, 0.01% potassium nitrate, with an incubation temperature 

of 25°C (Maguire and Sedgley 1997a). Germination after six months remained 

constant at around 70% in all treatments, except 20°C storage, which gave only 25% 

germination. Pollen viability was assessed using fluorescein diacetate, but the results 

did not reflect the loss of germinability at 20°C and correlation with in vitro results 

were variable. There was no effect of floret position on the inflorescence on germination, 

but pollen viability varied over the flowering period with maximum germination midseason. 

16 

B. Selection 

Strict criteria based upon commercial requirements must be applied to the 

population under selection (Sedgley 1995c,d). These include size, number, quality and 

color of blooms, stem length, time of flowering, length of the flowering period, vase 

life, disease tolerance, and ease of vegetative propagation. Quality is a very complex set 

of characteristics, comprising stem length and straightness, with minimal leaf damage and 

abnormal florets (Fuss and Sedgley 1991a). Adequate testing of superior selections is 

required, as some characters, such as bloom color, may alter during the flowering season 

(Bickford and Sedgley 1994, 1995). In the red, pink, apricot, yellow, and bronze variants 

of B. menziesii, the overall inflorescence color derives from the combination of style and 

perianth, which may comprise different hues. Where anthocyanin pigments are 

responsible for the color, intensity may vary with temperature and thus with season and 

location. Selection for color stable variants is an important aim of B. menziesii 

improvement. 

RAPD-PCR can be used to generate fingerprints specific for each new cultivar of 

Banksia, to aid in identification and registration (Maguire et al. 1994; Sedgley 1995a,b). 

There is also potential to use the method in marker-aided selection, to accelerate progress, 

as plants do not need to be grown to maturity from seed before they can be assessed 

horticulturally. 

C. Interspecific Compatibility 

For most horticultural crops, significant gains in productivity, quality, and 

novelty have resulted from chance or deliberate interspecific hybridization, and 

research on Banksia has addressed this aspect of reproductive biology. Experimentation 

has focused on the commercial cut flower species, with interspecific sexual compatibility 

investigated in B. prionotes, B. hookeriana, B. menziesii, and B. coccinea (Tables 1.1, 

1.2). Some species supported no germination of interspecific pollen, some supported 

normal pollen tube growth, and others produced pollen tube abnormalities, including 

thickened walls, bulbous swellings, directionless growth, burst tips, and branched tubes 

(Sedgley et al. 1994, 1996; Maguire and Sedgley 1997b). Control of pollen tube growth in 

the pistil was imposed in the pollen presenter and upper style. A number of species 

combinations showed pollen tube growth to the base of the style, but only the B. 

hookeriana by B. prionotes cross has so far resulted in seed set (Table 1.2). Given that

intraspecific seed set of Banksia is very low, in the order of 3.5% (Sedgley et al. 1996), it 

is important to repeat the crosses that showed pollen tube growth to the base of the style, 

with higher numbers of pollinations. 

Table 1.2. Banksia interspecific combinations with pollen tube growth to the base of the 

style or with viable seed set (Sedgley et al. 1994, 1996; Maguire and Sedgley 1997b). 

Female parent Male parent Pollen tube growth Viable seed set 

B. menziesii B. baxteri Yes No 

B. speciosa Yes No 

B. candolleana Yes No 

B. prionotes Yes No 

B. burdettii Yes No 

B. tricuspis Yes No 

B. prionotes B. baxteri Yes No 

B. speciosa Yes No 

B. elderiana Yes No 

B. coccinea Yes No 

B. brownii Yes No 

B. tricuspis Yes No 

B. hookeriana B. prionotes Yes Yes 

B. coccinea B. ericifolia Yes No 

B. micrantha Yes No 

B. sphaerocarpa Yes No 

Natural interspecific hybrids have occurred, both in the wild and under 

cultivation (Taylor and Hopper 1988), including crosses between B. hookeriana and B. 

prionotes. One such putative hybrid with horticultural merit, registered as the cultivar 

‘Waite Orange’ (Sedgley 1991), was studied using morphological, sexual, and 

biochemical characters (Sedgley et al. 1994, 1996). Hybrid status of 'Waite Orange' 

was confirmed using morphological characters, and controlled pollination showed 

that the hybrid was fertile following controlled selfing and backcrossing to both parental 

species, as well as following open pollination, but that seed set was lower than for the 

parental species. In addition, interspecific hybridization between B. hookeriana and B. 

prionotes was investigated via pollen tube growth, seed set, and morphological 

measurements. Pollen tube growth to the ovary was observed following self and cross 

intraspecific pollination of both species and following interspecific hybridization to B. 

hookeriana as the seed parent, but not in the reciprocal cross. All crosses resulted in seed 

set, except for self pollination of B. prionotes and interspecific pollination to B. prionotes 

as the seed parent. Mortality of hybrid seedlings was high. RAPD analysis of hybrid 

seedlings from two families showed the presence of paternal B. prionotes bands in all 

11 seedlings tested. Leaf length or width of nine hybrid seedlings that survived to the ten 

leaf stage was intermediate between that of intraspecific seedlings of both parents at the 

same age. It was concluded that hybridization between B. hookeriana and B. prionotes 

is unilateral, with interspecific seed set of B. hookeriana comparable to that following 

intraspecific pollination. Isozyme and AP-PCR analysis confirmed that the two parent 

species were closely related. 

17

18 

D. Cultivars 

Banksia species are relatively new to the cut flower industry, and there has been 

little emphasis placed on cultivar development. There are seven named cultivars of 

Banksia for amenity use, but only three for cut flower production, and all are 

propagated vegetatively to perpetuate their superior varietal characteristics. The ten 

named cultivars were derived from open pollinated populations under cultivation, and 

none so far has resulted from controlled hybridization. 

Of the seven cultivars for environmental horticulture, three are prostrate forms. 

'Celia Rosser' is derived from an open-pollinated seedling of B. canei. It has deeply 

lobed leaves, a prostrate growth habit, and yellow inflorescences. 'Austraflora Pygmy 

Possum' is a coastal low-growing form of B. serrata, and ‘Roller Coaster’ is a prostrate 

variant of B. integrifolia. The other four cultivars have the more usual upright habit of 

Banksia species. ‘Limelight’ is a sport of B. ericifolia with lime green foliage, ‘Giant 

Candles’ is an interspecific hybrid between B. ericifolia and B. spinulosa var. spinulosa 

that arose in cultivation, ‘Lemon Glow’ is a yellow-flowered form of B. spinulosa var. 

cunninghamii, and ‘Birthday Candles’ is a dwarf form of B. spinulosa var. spinulosa. All 

of these varieties are for garden use, with ‘Birthday Candles’ for pot and garden 

cultivation. 

There are three terminal-flowering cultivars for cut flower production. ‘Waite 

Orange’ (Fig. 1.1) is a natural interspecific hybrid between B. hookeriana and B. 

prionotes, that flowers between the peak period of the two parental species and so 

extends the season for production of orange Banksia blooms (Sedgley 1991, 1995c,d). 

‘Waite Crimson’ is a mid-season dark red selection of B. coccinea (Sedgley 1995a), and 

‘Waite Flame’ is an early season orange-red selection, also of B. coccinea (Sedgley 

1995b). 

V. PHYSIOLOGY 

A. Flowering 

Floral intitation of the species B. coccinea, B. menziesii, B. hookeriana, and B. 

baxteri occurs between October and December, the southern hemisphere late spring and 

early summer (Fuss et al. 1992; Rohl et al. 1994). Although floral initiation occurs at 

roughly the same time of year in all four species, flowering does not, and the main 

difference between them is in the rate of development of the initiated inflorescences. This 

is very important commercially, as it means that pruning must be carried out prior to 

October, even in the late-flowering species such as B. coccinea, or the grower risks 

removing initiated blooms for the next year's harvest (Sedgley and Fuss 1992). Only the 

thickest shoots will initiate an inflorescence, and the likelihood of a shoot producing a 

bloom is correlated with shoot age and shoot size. The age of a shoot is determined from the 

number of bud scar rings, with two-year-old shoots having a ring of bud scale scars at the 

base, and another ring half way along the shoot. Most blooms are produced on shoots that 

are two years old, with only a minority produced on one- or three-year-old shoots. Thus, 

each shoot must be allowed to develop for two years before a bloom can be expected, and 

some shoots never produce blooms. These are thin and weak compared with those that do, 

and there is a minimum shoot diameter, measured at the bud scar ring at the base of 

the current flush growth, which must be achieved for a shoot to flower. The critical 

diameter is 4.5 mm for B. coccinea, 6 mm for B. menziesii, 8 mm for B. hookeriana, and 11 

mm for B. baxteri, and the information has been used to develop a pruning strategy for 

Banksia (Sedgley and Fuss 1992). High light intensity is also important for successful 

flowering of Banksia, with pruning to prevent shading an important consideration. 

Floral initiation in the southern hemisphere late spring or early summer indicates 

that the environmental cues of increasing temperature and daylength may be important. 

This has been confirmed by experiments in which plants of B. coccinea and B.

hookeriana were grown in environmental growth chambers, with full control of 

temperature and daylength (Rieger and Sedgley 1996). Four sets of conditions were 

imposed, with 8 and 16 h daylength, each with two temperature regimes of 15/10°C 

(day/night) and 25/20°C. For B. coccinea, most floral initiation occurred at 16 h 25/20 ° C 

and 16 h 15/10°C, with less initiation at 8 h 15/10°C and none at 8 h 25/20°C. This 

indicates that long daylength may be the environmental trigger for flowering in this 

species. For B. hookeriana, both the 16 and 8 h 25/20°C treatments stimulated flowering, 

with no floral initiation at 15/10°C with either 16 or 8 h daylength. This indicates that for B. 

hookeriana temperature has the major control over floral initiation. 

Manipulation of Banksia flowering, to induce early or late flowering or to extend 

the production season, is not currently practised, but these research results introduce the 

possibility for extension of the flowering period of B. coccinea. By using supplementary 

lights to increase the natural daylength during winter, it may be possible to induce the 

plants to initiate earlier, and so possibly to flower earlier. Extension of the flowering 

period by inducing late initiation is more of a problem, as the plants would need short 

days at a time when natural daylength is increasing. While this is difficult in the 

field, it may be possible under protection. Manipulation of temperature, as required for B. 

hookeriana, could also be achieved under cover. 

The Banksia bloom is an inflorescence comprising many hundreds of individual 

flowers; if initiation is incomplete, it can result in uneven or truncated blooms. Low 

temperature effects appear to be particularly common, correlating with abnormal blooms 

of B. coccinea (Fuss and Sedgley 1991a) and B. menziesii (Fuss et al. 1992). Careful site 

selection and provision of windbreaks or shelter are the most effective means of 

controlling the problem. 

B. Propagation 

Banksia seeds are encased by woody follicles in cone-like infructescences. The 

follicles of most species are adapted to open only after fire (Elliot and Jones 1992), 

although there are exceptions to this rule, including B. marginata and B. integrifolia 

(Wardrop 1983). Heat generated during a wildfire melts adhesive material sealing the 

follicle, and the effect can be simulated in a fire or oven. A period of rain after the 

wildfire is important in some species, and this can be simulated by submerging the 

infructescences in cold water for between one and three days, followed by sun drying 

(Elliot and Jones 1992). In contrast to some other genera of Proteaceae, the seeds of Banksia 

species require no germination pre-treatment. They are generally large and rich in 

nutrients (Pate et al. 1986), and so tend to have high germination success rates. The 

temperature optimum for germination varies with species, from 18-23°C for B. integrifolia 

to 28-32°C for B, aemula (Heslehurst 1979), with 10-25°C the best range for B. coccinea 

(Bennell and Barth 1986a). For germination of B. coccinea, B. aculeata, and B. ornata, 

l5°C is the optimum temperature, with 70% germination of B. aculeata seed at 25°C as 

compared with 100% at 15°C. Germination rate is slow, with first emergence after about 

three weeks, but taking up to three months for complete germination. Following germination, 

seedling growth is fastest at 25°C. 

Propagation of Banksia species by rooted cuttings is variable (Bennell and Barth 

1986a), and is based on semi-hardwood material collected following the spring growth 

flush, during the cooler months of the year. Some species will produce roots with no auxin 

treatment (George 1984), although better results are achieved with 3,500 ppm 

indolebutyric acid (IBA) for most species. The highest strike rates for B. coccinea were 

achieved with 8,000 to 12,000 ppm IBA (Bennell and Barth 1986a), and although some 

cuttings produced roots at all concentrations tested, root development was better with IBA 

than without. Genotype also influences rooting, with variation from 0 to 80% success 

for different individuals of B. hookeriana and B. prionotes (Sedgley 1995c,d). 

Success with micropropagation has resulted in culture establishment of B. coccinea, 

B. ericifolia, B. lemanniana, B. marginata, B. menziesii, B. ornata, B. prionotes, B. serrata, 

19

and B. spinulosa var. collina from nodal segments and shoot tips (K. M. Tynan, E. S. Scott, 

and M. Sedgley unpublished). Murashige and Skoog medium with benzyladenine resulted 

in slow growth and multiplication rates, with shoot formation on cultures of B. coccinea and 

B. spinu]osa var. collina. Roots were induced on excised shoots of B. coccinea using filter 

paper bridges over liquid medium, but there has been little success so far in hardening off 

rooted explants. 

There has been little consistent success with grafting and budding of Banksia 

species. Rootstocks used for experimentation are generally seedlings of B. 

integrifolia, B. spinulosa, and B. marginata that are tolerant of heavy soils and of the root 

rot fungus Phytophthora cinnamomi Rands (McCredie et al. 1985a). Bennell and Barth 

(1986b) used a wedge graft for field-grown scions of B. coccinea and B. menziesii, which 

had been girdled four weeks prior to grafting. The overall success rate for both species 

was between 30 and 40% at 20 weeks, but a further complication is that grafts may 

survive for a number of years, with the union failing under conditions of stress (Elliot and 

Jones 1992). At present the success rate does not justify commercial use of grafting for 

Banksia, and further research is needed into graft compatibility. 

20 

C. Water and Nutrient Uptake 

Most species of Banksia are native to the Mediterranean climate areas of southwestern 

Australia, with some from south-eastern Australia and one tropical species that 

extends into New Guinea and the Aru Islands (George 1987). All species grow best in light 

sandy soils of acid pH, and the south-western Australian species are particularly intolerant 

of heavy soils. Most are adapted to a hot, arid summer prone to bushfires, and have 

developed strategies to cope with these conditions (Cowling and Lamont 1986). They are 

adapted to poor soils of low nutritional status, particularly phosphorus, and develop 

proteoid roots for increased nutrient absorption (Lamont 1986; Low and Lamont 1986). 

Proteoid roots are specialisations for solubilization of soil phosphates (Grierson and 

Attiwill, 1989), and to increase the root surface area for absorption. In the native habitat 

they are major exporters to other parts of the plant of phosphate, potassium, and amino acids 

during the wet winter season (Jeschke and Pate 1995). 

The Banksia root system is dimorphic, with proteoid root-bearing shallow 

lateral roots in the top 15 cm, and a single tap or sinker root extending down to 7 m, or 

to the water table if located higher than this depth (Low and Lamont 1990; Dodd and Bell 

1993; Pate et al. 1995). Proteoid roots die during the arid summer, and regenerate 

during the wet winter of the native habitat, while shoot growth patterns are the reverse, 

with extension during summer. The amount of water required by Banksia plants of 

different ages has not been determined, but water stress can be a limitation to seedling 

establishment in the wild (Burgman and Lamont 1992; Enright and Lamont 1992). 

Investigation of xylem and phloem sap of B. prionotes indicates that lateral root xylem sap 

is more concentrated in virtually all solutes than that of sinker roots, even during the dry 

summer following senescence of the proteoid roots (Jeschke and Pate 1995). Gradients in 

xylem sap concentration suggest lateral abstraction and storage of incoming phosphate 

in basal stem parts during winter with subsequent release to the xylem in summer for 

the growing period. Phloem sap is more concentrated than xylem sap in nutrient ions 

and amino acids. 

Under cultivation, phosphorus toxicity can be a problem for Banksia species, with 

symptoms reported in cut flower plantings with soil levels of greater than 40 ppm. In a 

detailed study, interactive effects between phosphorus and iron have been reported in B. 

ericifolia subsp. ericifolia grown in soilless potting medium (Handreck 1991). As the 

phosphorus level was increased, iron deficiency symptoms increased, indicating 

preferential translocation of phosphorus over iron. The ideal ratio of phosphorus to iron in 

the medium was around 2 0, in media containing less than 3 mg/L phosphorus and 1. 5 g/L 

iron. An important feature of Banksia biology is that high levels of nutrients are 

concentrated in the seeds to give seedlings an advantage in the poor native soils of

Australia (Groves et al. 1986; Pate et al. 1986). 

D. Postharvest Physiology 

Relatively little research has been conducted on preservative or pulsing solutions 

for fresh Banksia cut blooms, but sucrose pulsing generally does not enhance quality or 

longevity, and concentrations above 2% are detrimental. Work with B. coccinea found no 

effect of sucrose pulsing, with blooms having a vase life of 15 days in water plus 0.01% 

chlorine (Delaporte et al. 1997). Hydroxy quinoline sulphate is detrimental, as it causes 

reduction in vase life and accelerated opening of the florets. Cold dry storage is possible at 

2°C and 100% relative humidity in darkness for 14 days, after which there is a 10-day 

vase life. 

Research aimed at postharvest insect removal has tested a range of measures 

(Seaton and Joyce 1992, 1993). Conventional disinfestation methods involving chemical 

control have no phytotoxic effects on B. hookeriana blooms, but there is a need to 

develop alternative methods for safety reasons. Gamma irradiation is unsuitable because it 

damages Banksia blooms (Seaton and Joyce 1992), as do volatiles such as acetaldehyde, 

although to a lesser extent. Low temperature and high carbon dioxide treatments show 

promise for Banksia stems, as all test insects are killed by 10 to 14 days storage at 

1°C, with a reduction to seven days if 45-60% CO2 is combined with the low 

temperature treatment (Seaton and Joyce 1993). B. hookeriana has an acceptable vase life 

following treatment of up to 28 days at 1°C. Hot water dips are less successful, with 

Banksia blooms damaged by all treatments that kill insects. 

Lower-quality blooms unsuitable as fresh stems are often dried. For natural 

drying the blooms are hung, and the process can be accelerated by solar heating, hot air 

dryers, dehumidifiers, microwaving, freezing, and dehydration using silica gel. The 

colors of both flowers and leaves fade under these conditions, and sulfuring to preserve 

color is achieved either by burning elemental sulfur or by using sulfur dioxide gas in an 

enclosed area. The orange Banksia species and B. menziesii respond well to sulfuring. 

Stems can be bleached using hypochlorite, chlorite, peroxide, or hydrosufite (Dubois 

and Joyce 1992), or preserved by placing in 10% glycerine for 24 h before drying. This 

latter treatment gives a shiny gloss to the dried product, which retains flexibility. It is 

not suitable for cut blooms, as these damage easily when treated with glycerine. 

Dyed Banksia blooms are popular for some markets. Blooms of pale colored 

species such as B. baxteri, B. speciosa, and the unopened buff colored flowers of the 

orange species are dipped into aniline or water-soluble dyes. These impart a wide 

range of bright, vibrant colors, including blue, purple, orange, red, and green, or 

combinations. Uptake dyes produce more subtle colors but are not much used. 

VI. PRODUCTION 

A. Culture 

Banksia species are cultivated almost exclusively without protection and 

planted directly into soil. There has been little attempt at protected cultivation, although B. 

menziesii can be grown experimentally in nutrient solution (Avidan et al. 1983 cited by 

Ben-Jaacov et al. 1989). Between-plant spacings vary from 2 m for the more compact 

species such as B. coccinea to 3.5 m for the more spreading B. speciosa and B. 

prionotes, with between-row spacings of between 3 and 6.5 m (Sedgley 1996). 

Windbreaks, weed removal, and rabbit protection are often used, and a mulch of a freelydraining 

medium such as gravel or coarse sand aids in protection of the roots from 

extremes of temperature. Drippers or microjets are the most efficient for irrigation, and 

tensiometer studies indicate that in Australia irrigation of 4 litres per plant per day is 

advisable in all except the winter months. Application of nitrogen, potassium, and iron 

are important, but high levels of phosphorus are generally avoided, with slow-release 

21

low-phosphorus fertilizer used in most nurseries. Healthy growth has been recorded with 

0.5 g urea plus 0.5 g potassium chloride applied per plant through the irrigation system 

every six weeks, with 1 g ammonium nitrate and 1 g potassium sulfate per week during 

the active growth and flowering period. Iron chelate is also applied when chlorosis is a 

problem. 

22 

B. Diseases and Pests 

The most important disease of Banksia species, both in the wild and under 

cultivation, is root rot caused by the pathogen Phytophthora cinnamomi. The disease is 

soil borne, and is readily transmitted on feet, vehicles, tools, and by water. In the 

nursery, the disease causes damping off of seedlings. In the field, poor growth is followed 

by drying and wilting of the foliage, because by the time above-ground symptoms are 

visible, the root system has been heavily colonised. In addition to dead roots, there is 

often collar rot at ground level. It has been recorded that a number of other Phytophthora 

species infect Banksia plants, particularly in nurseries. These include P. dreshsleri 

Tucker, P. nicotianae Waterhouse, P. cactorum Schrot., and P. citricola Sawada 

(Hardy and Sivasithamparam 1988; Tynan et al. 1995). 

Control of Phytophthora is very difficult. Introduction of the disease to a new 

nursery or planting should be avoided, as it is impossible to eradicate the disease once 

it is established, and it can survive in soil without a host for many years. The 

development of Phytophthora-tolerant cultivars may be possible (Tynan et al. 1995), as 

there is both between and within species variability (Cho 1981, 1983; McCredie et al. 

1985a,b). Tolerance screening requires an effective non-destructive method (Dixon et 

al. 1984), and an excised root assay appears to be the most reliable (Tynan et al. 1995). 

Another promising approach is the use of antagonistic biological control agents; the 

bacterium Pseudomonas cepacia Burkh. has been used to suppress the effects of the 

disease in the nursery (Turnbull et al. 1992). Grafting of susceptible types onto tolerant 

species has been suggested as an alternative control measure for the field (McCredie et al. 

1985a), but grafting success to date has not reached commercial levels. Chemicals can be 

used to combat Phytophthora, but eradication of the fungus from infected land is 

difficult, and there may be phytotoxic effects. 

Banksia species are attacked by relatively few pests, and most are insects that 

cause damage to the blooms or seeds (Scott 1982; Zammit and Hood 1986; Wallace and 

O'Dowd 1989; Woods 1988; Vaughton 1990). Tunnelling moth larvae (Arotrophora spp.) 

are the most common of the Banksia flower caterpillars, both under cultivation and in 

the wild. The adult moth lays eggs on immature blooms and the larvae move into the 

center of the inflorescence stem and kill large numbers of flowers by feeding on the soft 

tissue. The larvae pupate in the flower stem, and control is difficult because they are 

protected within the inflorescence rachis. Larvae of a number of Lepidopteran genera may 

cause damage by feeding on flowers, including Cryptophasa sp., Peraglyphis idiogenes 

Common, and Xyloryctis spp. The Coleopteran Myositta has been reported on B. menziesii 

flowers in the wild, and leaf damage can be caused by the chewing snout beetle, 

Catosarcus sp. In contrast to the small number of flower predators, a wide range of insect 

genera has been recorded feeding on seeds within the Banksia infructescence. These 

include Lepidopterans of the genera Arotrophora, Chalarotona, Scieropepla, Xyloryeta, 

Xyloryctis, Brachmia, and Carposina, the Coleopterans Alphitopis nivea Pascoe, Cechides 

amoenus Pascoe, and Myositta spp, and unidentified Coleopteran weevils. 

Banksia seeds form part of the natural diet of parrots and cockatoos, and cones are 

often predated in cultivated plantings and in the wild (Vaughton 1990; Witkowski et 

al. 1991). Predators include the crimson rosella, Platycereus elegans Gmelin, and the 

yellow-tailed black cockatoo, Calyptorhynchus funereus Shaw. Open blooms are often 

removed from the plant, as well as cones with developing seeds.

VII. CONCLUSIONS 

Banksia species are already established as cut flower crops, and are amongst 

the most readily identifiable of Australian native plants (Plate I). They are accepted on 

international markets and demand currently exceeds supply. This situation will not 

continue indefinitely, and while lesser quality may be acceptable in a sellers' market, 

this will not be the case as supply increases. Considerably more research is needed into 

all aspects of Banksia production so that stems can compete with the high standard 

expected of established cut flower crops such as rose and carnation. 

In addition to making good commercial sense, there are strong environmental 

reasons why further research into Banksia biology is essential. Until the early 1980s, 

most Banksia stems for the cut flower market were bush picked from the native habitat, 

particularly in south-western Australia (Pegrum 1988), and Banksia is still the second 

largest bush picked genus in Australia. This has resulted in major damage to natural 

ecosystems via disturbance, introduction of disease, and depletion of seed reserves. 

Soil and plant destruction is caused by access vehicles, and soil-borne diseases are 

spread on tires and footwear. The root rot fungus Phytophthora cinnamomi attacks a 

wide range of native genera, including Banksia, and is very readily distributed (Shearer 

et al. 1991). The aerial canker diseases Diplodina sp., Zythiostroma spp., and 

Botryosphaeria ribis Gossenb. & Dugger are spread via infected secateurs, and have been 

the cause of more recent concern. Diplodina cankers girdle branches and eventually 

kill the plant, the disease being most prevalent in stands aged over 12 years. Removal of 

blooms depletes the seed bank and has implications for continued regeneration. 

Legislation is now in place to prevent bush picking of B. coccinea and B. baxteri from 

crown land, and this has resulted in an increase in Banksia plantings for cut flower 

production. 

The visual appeal of Banksia blooms is unquestioned, but there are other features 

that will ensure continued popularity, including long shelf life and variety of color and 

form. Continued research input into production problems is needed to ensure stability of 

the international industry in a new but increasingly popular cut flower commodity. 

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29:663-671. 

Fuss, A. M., S. J. Pattison, D. Aspinall, and M. Sedgley. 1992. Shoot growth in relation to 

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Scientia Hort. 49:323-334. 

Fuss, A. M., and M. Sedgley. 1990. Floral initiation and development in Banksia coccinea 

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Fuss, A. M., and M. Sedgley. 1991a. Variability in cut flower production of Banksia 

coccinea R.Br. and Banksia menziesii R. Br. at six locations in southern Australia. 

Austral. J. Expt. Agr. 31:853-858. 

Fuss, A. M., and M. Sedgley. 1991b. Pollen tube growth and seed set of Banksia coccinea 

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Fuss, A. M., and M. Sedgley. 1991c. The development of hybridisation techniques for 

Banksia menziesii for cut flower production. J. Hort. Sci. 66:357-365. 

George, A. S. 1981. The genus Banksia L.f. (Proteaceae). Nuytsia 3:239-473. 

George, A. S. 1984. The remarkable banksias. Wildflowers of great potential. Austral. 

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George, A. S. 1987. The Banksia Book. Kangaroo Press, Austral. 

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George, A. S. 1996. Notes on Banksia L.f. (Proteaceae). Nuytsia 11:21-24. 

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Groves, R. H., P. J. Hockin, and A. McMahon. 1986. Distribution of biomass, nitrogen, 

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24

Handreck, K. A. (1991). Interactions between iron and phosphorus in the nutrition of 

Banksia ericifolia L.f. var. ericifolia (Proteaceae) in soil-less potting media. Austral. J. 

Bot. 39:373-384. 

Hardy, G. E., and K. Sivasithamparam. 1988. Phytophthora spp. associated with containergrown 

plants in nurseries in Western Australia. Plant Dis. 72:435-437. 

Heslehurst, M. R. 1979. Germination of some Banksia species. Austral. Plants 10:176-177. 

Jeschke, W. D., and J. S. Pate. 1995. Mineral nutrition and transport in xylem and phloem of 

Banksia prionotes (Proteaceae), a tree with dimorphic root morphology. J. Expt. Bot. 

46:895-905. 

Jones, R. B., R. McConchie, W. G. van Doorn, and M. S. Reid. 1995. Leaf blackening in cut 

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Lamont, B. B. 1986. The significance of proteoid roots in proteas. Acta Hort. 185:163-170. 

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Hort. 18: 889-899. 

Low, A. B., and B. B. Lamont. 1990. Aerial and below-ground phytomass of Banksia 

scrub-heath at Eneabba, South-western Australia. Austral. J. Bot. 38:351-359. 

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637. 

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25

Scott, J. K. 1980. Estimation of the outcrossing rate for Banksia attenuata R.Br. and Banksia 

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155:755-762. 

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between Banksia hookeriana Meisn, and B. prionotes Lindl. (Proteaceae). Int. J. 

Plant Sci. 157:638-643. 

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into the influence of Pseudomonas cepacia on infection and survival of proteas in 

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Phytophthora dieback in banksias: screening for resistance. Acta Hort. 387:159-162. 

Vaughton, G. 1990. Predation by insects limits seed production in Banksia spinulosa var. 

neoanglica (Proteaceae). Austral. J. Bot. 38:335-340. 

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by insects on fruit-set by Banksia spinulosa. Oecologia 79:482-488. 

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Austral. J. Bot. 31:485-500. 

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co-occurring banksias in souths coastal Western Australia: the role of plant age, 

cockatoos, senescence and interfire establishment. Austral. J. Bot. 39:385-397. 

Woods, W. 1988. Pests of native flowers. J. Agr. Western Austral. 29:119-121. 

Zammit, C., and C. W. Hood. 1986. Impact of flower and seed predators on seed-set in two 

Banksia shrubs. Austral. J. Ecol. 11:187-193. 

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Banksia shrubs at various times after fire. Vegetatio 70:11-20. 

26

Leucospermum: Botany and 

Horticulture ∗ 



ISBN 0-471-25444-4 © John Wiley & 

Sons, Inc. 

by: Richard A. Criley 

∗ Published as journal Series No. 4303 of the College of Tropical Agriculture and Human 

Resources, University of Hawaii, Honolulu, HI. Acknowledgment is made to Dr. Philip 

E. Parvin and Dr. Gert J. Brits for their assistance in the preparation of this review. 

2 

27


The Proteaceae embrace 82 genera, of which the most important cut flower genera 

are Protea, Leucospermum, Leucadendron, Banksia (Sedgley 1998), and Grevillea 

(Joyce et al. 1997), all of which also have species used as cut foliages (Parvin 

1991a) and landscape material. The nut crop, Macadamia, is one of the other prized 

members of the Proteaceae. In this review, the noun protea (proteaceous when used as 

an adjective) is used in a general sense for the cut flower members of the family, while 

a genus name is used where it was clearly identified in a citation. 

Venkata Rao (1971) noted, perhaps incorrectly, that the family Proteaceae 

contains very few plants of economic importance but that most are rich nectar producers 

and of value to apiarists. Indeed, it is the copious nectar production in some ornithophilous 

species of Protea that may lead to the black leaf disorder of the cut flower (Dai and Paull 

1995; Jones et al. 1995). Many proteaceous species are adapted to pollination by birds, 

and the large solitary inflorescences of these have also attracted the interest of humans 

because of their ornamental qualities. 

Brits et al. (1983) reviewed the development of proteas as cultivated crops in 

South Africa. In his introduction to the first newsletter of the International Protea 

Association, G. J. Brits (1984) noted that many South African flowering plants were 

developed as horticultural crops in Europe, but despite early attempts to cultivate proteas 

in Europe their specialized horticultural requirements prevented them from incurring a 

similar fate. The distribution of the Proteaceae is linked to the occurrence of acid soils 

that are extremely deficient in plant nutrients. This linkage continues to frustrate 

horticulturists who are used to nurturing their plants with fertilizers. 

Proteas were first cultivated seriously in the early 1900s at the National 

Botanic Gardens at Kirstenbosch in the Cape Province of South Africa, but they had been 

gathered from mountain veld even earlier and marketed in Cape Town, where an 

appreciation and acceptance of these cut flowers developed. Following public concern 

about the pressure that wild flower harvesting was having on the habitat, in 1920 the 

Kirstenbosch Botanical Gardens encouraged the founding of the "Society for the 

Protection of Wild Flowers," whose early emphasis was the planting of veld 

flowers to protect the native flora, a "planting brigade rather than a plucking 

brigade" according to their original brochure (Brits 1984; Rourke 1980). The 

progression of proteas in their development as a commercial crop is illustrated in Table 

2.1. The use of plantings of selected clonal material is still expanding, while the last 

stage, use of clonal materials from genetic manipulation, has not begun. 

The first South African publication on the cultivation of proteas appeared in 

1921 (Matthews 1921). This historic, but almost forgotten, article was the forerunner of 

the vast popular literature available today. Some cultural guides of more recent standing 

include publications by Vogts (1958, 1960, 1962, 1979, 1980, 1982), Watson and Parvin 

(1970), Furuta (1983), Harre (1988b, 1995), Matthews (1993), and McLennan (1993). 

The foundations for commercial protea cultivation in the Western Cape of South Africa 

were established during the 1940s to the 1970s by Frank C. Batchelor, who conducted 

the first breeding efforts, collected natural hybrids and established vegetatively 

propagated plants, set standards of quality, marketed cultivated proteas overseas, 

founded the forerunner of South African Protea Producers and Exporters Association 

(SAPPEX), and identified production research needs. During the 1950s, Marie Vogts 

gathered the known information about proteas and published it (Vogts 1958). She also 

identified areas needing more research (Vogts 1960) and played a key role in limiting 

the damage to wild populations by publishing cultural methods (Vogts 1962, 1979; 

Vogts et al. 1972). 

By the 1960s, a small number of managed "flower orchards" were producing 

flowers of better quality than most of those gathered from the wild, and the 

introduction of refrigeration facilities in the 1980s improved keeping quality prior 

to long-distance shipment. Flower importers in the northern hemisphere wanted 

28

continuous supplies of the same species throughout the year, whereas most of the proteas 

being shipped were highly seasonal. A partial solution to this problem has been to 

gather early- and late-flowering variants to lengthen the season. More recently, the 

Fynbos Unit of the South African Agricultural Research Council has been breeding in 

the important genera of proteas to develop a longer flowering period (Brits 1978, 1992a, 

1992b; Littlejohn et al. 1995; van Vuuren 1995). 

Table 2.1. Development of proteas as commercial cut flowers from harvesting in the wild to 

selection and development of clonal materials. Adapted from: Matthews and Matthews 

1994. 

Stage Characteristics Quantity & quality 

1. Harvesting from 

naturally occurring 

proteas in the wild 

2. Plantations raised 

from seed 

3. Plantations from 

vegetatively 

propagated material 

4. Plantations of selected 

clonal material 

5. Clonal materials from 

genetic manipulation 

and propagation by 

tissue culture 

No control of production, 

weather-dependent, no 

disease control, high 

picking costs 

Efficient layout, disease 

control possible, use of 

irrigation, 

replacement rate 

high 

Stock improved by 

selection from best 

seedling materials 

Selection from breeding 

programs for: flower and 

leaf life, stem length, 

disease resistance, 

packing and shipping 

qualities, flowering 

time, productivity 

Rapid response to market 

requirements for color, 

vaselife, stem length. 

Rapid response to disease 

problems 

Quality and quantity 

unreliable 

Improved reliability and 

quality, but flower forms 

variable 

Improved reliability and 

quality, quantities a 

function 

numbers 

of plant 

Reliable supplies, 

premium flower quality, 

uniform product, high 

productivity 

Premium quality flowers 

that exactly meet market 

needs, uniform product, 

high productivity, and 

highly competitive with 

other flower crops 

During the 20th International Horticultural Congress (1978) in Sydney, Australia, 

growers and researchers from South Africa, Hawaii, Israel, New Zealand, and Australia 

proposed the concept of an international organization to disseminate the information being 

generated in different parts of the world. The International Protea Association (IPA) was 

established in 1981 in Melbourne, Australia, by delegates to the first IPA Conference. The 

IPA initially represented the interests of growers and shippers, while the researchers formed 

the International Protea Working Group (IPWG) during 1984 meetings in Stellenbosch, 

South Africa, under the auspices of the Ornamental Section of the International Society for 

Horticultural Science. Recognizing a need to keep records on new cultivars as they were 

developed and released, the IPA supported establishment of the International Registration 

Authority for Proteas in Stellenbosch, South Africa (joan@pgb3.agric.za). It has recently 

published (Int. Reg. Auth. 1997) the fourth edition of the International Protea Register. 

Biennial meetings of the IPA and occasional concurrent meetings of the IPWG 

29

and IPA have been productive venues for the exchange of information between scientists 

and the commercial growers. Each produced its own publication for many years before 

they were merged in 1994, with the Protea News of IPWG now being published as part of 

the Journal of the International Protea Association. Four volumes of Acta Horticulturae 

(185, 254, 316, 387, and 453) present some of the most readily available information 

on proteas, but the newsletters and journals of the two organizations are largely 

unavailable outside the membership base. This review includes a generous sampling of 

information shared in these resources. 

The principal protea production areas initially were South Africa, California 

and Hawaii in the USA, Australia, and New Zealand. Israel's floriculture industry joined 

them in the mid-1970s following a visit and talks by California's leading protea grower, 

Howard Asper. Since then, interest in the production of proteas has spread to many other 

countries, and nascent production for export is underway in Spain (Canary Islands), 

Zimbabwe, France, Mexico, San Salvador, and Chile. 

Worldwide, there may be about 900 protea growers. Verifiable figures of the 

numbers of growers of Leucospermum are not possible to obtain, and even the figures on 

numbers of growers of Proteaceae are, at best, estimates. South Africa counts over 

300 producers affiliated with SAPPEX, while Australia has over 150 affiliated with 

the Australian Flora and Protea Growers Association. The sources for both figures estimate 

that perhaps twice as many smaller growers are not affiliated. Elsewhere, estimates are 40 

growers for New Zealand, 30 for Hawaii, 90 for California, and 55 for Israel. 

In 1983, at the founding of the IPA, it was estimated that a little over 800 ha were 

planted to cultivated proteas, while in the early 1990s, the area was 5 times greater 

(Parvin 1991b). South Africa registered the greatest increase in cultivated area as a result 

of pressures to reduce harvesting from the wild. A recent report (Malan 1997) 

estimated that 173,000 Leucospermum species and hybrid plants were established on 

66 ha in intensive cultivation as of 1996 and a harvest of 1.3 million stems was 

projected for 1997-98. In 1992, Zimbabwe was estimated to have about 240 ha of protea 

plantings (Harre 1992). Australia's native plant industry began to expand in the 1980s, 

reaching about 63 ha of cultivated Leucospermum in 1993 out of more than 945 ha 

devoted to native and introduced proteas (Turnbull 1997). Israel had about 20 ha of 

proteas (1.5 ha in Leucospermum) in 1992 (Meltzer 1992), with only 85,000 

Leucospermum stems sold at auction in 1995-96 (J. Ben-Jaacov, personal communication). 

The cultivated area for all proteas in Hawaii in 1996 was 66 ha (Hawaii Agr. Stat. Serv. 

1997) and in California 192 ha (Karen Robb, personal communication). 

Figures for the economic value of Leucospermum are hidden in the overall 

category of proteas, although figures from the Dutch auctions showed a per stem price 

for imported Leucospermums ranging from 0.75 to 0.70 (US$) in 1994-95. The per stem 

price for L. patersonii at auction in Israel was 76 cents in 1995-96 and 103 cents in the first 

three-quarters of the 1996-97 season (J. Ben-Jaacov, personal communication). In the 

USA, proteas are combined into the category of "other cut flowers" except for Hawaii, 

where the return to protea growers was $1.2 million in 1996 and in San Diego County of 

California where farm gate value (1996) was $3.57 million (Karen Robb, personal 

communication). A mid-90s figure for the farm gate value of Leucospermum in Australia 

was about one million dollars from 20 ha (David Matthews, personal communication). 

A figure of $12 million was estimated for the worldwide value of cut proteas in the late 

1980s, and this may represent less than 1/2% of the world's annual expenditure for 

flowers (Parvin 1991b). The proportion of this figure that Leucospermum represents is 

undetermined, although reports suggest it is about 10% (Forsyth 1992). 

30

II. BOTANY 

A. Origin and Ecology 

Before Australia, Antarctica, South America, and Africa drifted apart, they 

shared a zoological and botanical ancestry. Africa parted from the ancestral landmass 

about 120 million years ago, whereas South America and Australia separated about 70 

million years ago. Sir Joseph Hooker (cited in Venkata Rao 1971) observed in 1860, that 

the many bonds of affinity between the three southern floras, the Antarctic, Australian and African, 

indicate they have been members of one great vegetation which may once have covered as large a 

southern area as Europe now does the northern. The geographical changes that have resulted in its 

dismemberment into isolated groups scattered over a southern ocean must have been great indeed. 

The Proteaceae presently occur across the three temperate southern hemisphere 

continents (Australia, Africa, South America) that formerly were connected as 

Gondwanaland (Gondwana). The success of the dispersed members of the family has 

been attributed to inherent genetic plasticity (Dixon 1987). The concentration of 

Proteaceae in Australia (45 genera, 800+ species) argues for their origin there but 

endemism also exists in the African Proteaceae (16 genera, Rourke 1997), and no genera 

are common between the continents. South Africa presents great diversification in the 

subfamily Proteoideae (Vogts 1982). Proteaceous fossils dating from the early Tertiary 

period have been found in Victoria (Australia) as well as in Antarctica. The South 

American genera are evolutionarily closer to the eastern Australia taxa. Venkata Rao 

(1971) suggested that Proteaceae evolved in the mountainous rainforest conditions of 

eastern Australia in the Cretaceous period before spreading out into the lowlands and 

adapting to more xerophytic conditions. Western Australia and Africa are, in his view, 

secondary centers of diversification. The Proteaceae are largely distributed on soils of low 

nutrient content, often with acidic pH values. 

B. Morphology 

Leucospermum species are evergreen woody perennials with growth habits 

that range from small trees to spreading shrubs to prostrate ground covers. Some species 

produce a thickened lignotuber at ground level which contribute to vegetative 

regeneration of the plant following fires. The root systems are profusely branched with 

clusters of rootlets of limited growth appearing on the main roots. These are known as 

proteoid roots (Purnell 1960; Lamont 1986). Venkata Rao (1971) and Lamont (1986) state 

that proteoid roots are not mycorrhizal but may require a biological stimulus for their 

development. The leaves are simple, smooth to hairy, with entire to toothed margins. 

The inflorescences are manyflowered and resemble compositaceous clusters with short, 

thick receptacles subtended by involucral bracts. The flowers are simple with three basic 

whorls, the perianth, androecium, and gynoecium. The flowers are 4-merous, 

hermaphroditic, and perigynous (Venkata Rao 1971). Although the flowers are 

structurally regular, three posterior tepals are fused and the anterior one remains free so 

that the perianth is bilabiate. The style emerges through this discontinuity, and the tepals 

reflex to show reds, oranges, and yellows. Stamens are adnate to the tepals with the 

anther fused to the tepal midrib. Pollen grains are triporate and are shed before the stigma 

is receptive. The pistil has a long, curved style with a lateral stigma subtended by a 

pollen collecting apparatus. 

Rourke (1972) and Jacobs (1985) describe the inflorescence as a capitulum that 

develops from an axillary rather than a terminal bud, but that appears to arise distally. 

Inflorescences may be solitary, as in L. cordifolium, L. lineare, and L. vestitum, or 

in clusters (conflorescences), as in L. oleifolium, L. tottum, and L. mundii. The 

individual florets consist of a perianth formed by four fused perianth segments, one of 

31

which separates from the other three as the flower opens. The perianth curls back to display a 

prominent style; the striking appearance of the whole inflorescence of open flowers 

resembles a pincushion-thus one of the common names is pincushion protea. The styles, 

perianth, and involucral bracts may be white, yellow, pink, orange, or red and the 

combinations are responsible for the popularity of the pincushion proteas as cut flowers. 

The fruit of the Leucospermum is an indehiscent achene with a gelatinous 

pericarp (functionally, an elaiosome) and a tough seed coat consisting of several layers 

of sclerified cells. A reinterpretation of the pericarp-testa interface suggests that a 

crystalliferous layer found at this boundary is part of the testa outer integument rather 

than the pericarp (Manning and Brits, 1993). The embryology of Proteaceae has received 

considerable study by Venkata Rao (1971). The ovule is solitary and orthotropous and 

develops into a large (c. 8 mm), rounded seed, non-endospermic with mainly oily and 

proteinaceous food reserve. The species name, Leucospermum, which means "white 

seed," refers to the elaiosomes, which dry out to become pale and papery in 

herbarium specimens, but which are fatty, juicy coverings attractive to native ant 

species that drag the seed to shallow underground nests in the fynbos habitat. This may 

enable dispersal and germination (Brits 1987). 

32 

C. Taxonomy 

The Proteaceae consists of more than 1700 species in 82 genera, all of which occur 

in the southern hemisphere. The genus Leucospermum consists of 48 species (Table 

2.2, Plate 2) confined to southern Africa (Rourke 1972). Only a few species have been 

utilized as cut flowers (L. cordifolium, L. patersonii, L. lineare, L. 

conocarpodendron, L. vestitum), but natural and manmade interspecific hybrids 

exist as clonal selections that are grown commercially (Jacobs 1985). Other species are 

being examined for their potential to contribute disease resistance, foliage traits, and 

extended flowering seasons. 

Chromatographic analyses of 267 species and subspecies of all genera in the 

Proteaceae have contributed to an understanding of the evolutionary relationships 

within this family (Perold 1984, 1987). The phenolic compounds, leucodrin and its 

hydioxylated analogue, leudrin, and the diastereoisomer conocarpin and its ringopened 

methyl ester, reflexin, have been used to distinguish between Leucadendron 

and Leucospermum. Perold (1988) further demonstrated that the presence or absence of 

these phenolic compounds could be used in the characterization of Leucospermum 

hybrids. Both leucodrin and conocarpin are absent in L. cordifolium, L. lineare, and L. 

tottum, while leucodrin occurs in L. patersonii and its hybrids and conocarpin occurs in 

L. glabrum and its hybrids. 

Table 2.2. Leucospermum species and derivation of the species name (Rourke 1972, 

SAPPEX 1990, Rebelo 1995). 

Species Authority Derivation of name 

arenarium Rycroft Of sandy places 

bo usii Gandoger After H. Bolus 

calligerum (Gandoger) Gandoger & Schinz Bearing beauty 

catherinae Compton After Mrs. Catherine van der 

Byl and its catherine wheel 

appearance 

conocarpodendron (L.) Buek Cone-fruit-tree 

cordatum Phillips Heart-shaped 

cordifolium (Salisb. Ex Knight) Fourcade Heart-shaped leaf

cuneiforme (Burm. F.) Rourke Wedge-shaped 

erubescens Rourke Reddening 

formosum (Andr.) Sweet Beautiful 

fulgens Rourke Shiny 

gerrardii Stapf After W. T. Gerrard 

glabrum Phillips Hairless 

gracile (Salisb. Ex knight) Rourke Slender 

grandiflorum (Salisdb.) R. Br. Large/noble flower 

guenzii Meisn. After W. Guenzius 

hamatum Rourke Crooked 

harpagonatum Rourke Sickle-shaped 

heterophyllum (Thunb.) Rourke Various-leaved 

hypophyllocarpodendron (L.) Druce Under-leaf-fruit-tree 

innovans Rourke Novelty 

lineare R. Br. Linear 

muirii Phillips After J. Muir 

mundii Meisn After J. L. L. Mund 

oleifolium (Berg.) R. Br. Olive-leaf 

parile (Salisb. Ex Knight) Sweet Equal (similar to other species) 

patersonii Phillips After H. W. Paterson ? 

pedunculatum Klotzsch in Krauss Having a stalk 

pluridens Rourke Many-teeth 

praecox Rourke Flowering early 

pmemorsum (Meisn.) Phillips With end bitten off 

profugum Rourke Fleeing outwards 

prostratum (Thunb.) Stapf Lying on the ground 

reflexum Buek ex Meisn. Bent backwards 

rodolentum (Salisb. Ex Knight) Stapf Smelling like a rose 

royenifolium (Salisb. Ex Knight) Rourke Wild-coffee (Royena)-leaf 

saxatile (Salisb. Ex Knight) Rourke Of the rocks 

saxosum S. Moore Occurring among rocks 

secundifolium Rourke Unidirectional leaves 

spathulatum R. Br. Spoon-shaped 

tomentosum (Thunb.) R. Br. Woolly 

tottum (L.) R. Br. Native to the Cape (Hottentot) 

truncatum (Buek ex Mesin.) Rourke Cut off at tip 

truncatulum (Salisb. Ex Knight) Rourke Small, cut off at tip 

utriculosum Rourke Having a bladder 

vestitum (Lam.) Rourke Clothed 

winterii Rourke After J. Winter 

wittebergense Compton of the Wittenberg mountains 

A number of synonyms and botanical varieties have been collected under the above species by Rourke 

(1972). 

33

34 

D. Floral Physiology 

1. Flowering. 

Knowledge on flower initiation and development in Leucospermum was 

summarized in The Handbook of Flowering III (Jacobs 1985). He proposed that 

Leucospermum was a day-neutral plant in which flower initiation was evoked in 

response to high light intensity in conjunction with intraplant factors such as cessation of 

shoot growth and release of axillary buds from correlation inhibition. Jacobs et al. 

(1986) later separated flower growth and development into four stages: pre-floret 

(inflorescence bud initiation phase), floret initiation (floret primordium initiation phase), 

floret differentiation, and inflorescence enlargement. Plants grow vegetatively in spring 

and summer, with floret initiation commencing after shoot extension growth has ceased 

in fall. The pre-floret phase is characterized by slow growth and the development of bracts 

without florets in their axils. These bracts make up the involucre that covers the 

peduncle. In later-formed bracts, florets develop (the timeframe being mid-to-late 

fall), until cessation of floret initiation during the shortest days of winter (see also Criley 

et a1.1990). Inflorescences develop slowly through the winter months, then more rapidly 

as the days become longer and light intensity increases. Depending upon cultivar, 

flowering occurs in late winter through early spring or even into summer. 

For a period after cessation of shoot extension, pinching can induce vegetative 

growth from the upper axillary buds, indicating, according to Jacobs (1980, 1983), that the 

plants have not yet entered an induced state. By late fall, an induced state is achieved in 

a distal axillary bud, and other axillary buds are inhibited. Induction is relatively strong for 

the more distal buds and decreases basipetally. The developing inflorescence 

correlatively inhibits axillary buds below it (Jacobs 1980, 1983; Malan et a1. 1994a,b). 

Any of the top 6 to 10 lateral buds on a decapitated plant are capable of developing as an 

inflorescence. The 6 to 10 buds below the developing inflorescence develop to about 5 

mm in diameter as secondary inflorescence buds composed primarily of bract-like leaves 

and perianth initials, but they do not develop further unless the primary inflorescence is 

removed. Removal of the primary inflorescence bud during inductive short days leads to 

inflorescence initiation in 1 or 2 lateral buds, with a weaker effect the later in the 

season (Malan 1986). The developmental period of the secondary inflorescence buds 

becomes shorter the later in the spring that the primary inflorescence is removed due to 

more rapid accumulation of heat units in the ensuing spring and summer (Jacobs and 

Honeyborne 1979), however, the ability of a secondary bud to develop a flower declines 

the later the removal of the primary inflorescence (Jacobs and Honeyborne 1978; 

Malan et al. 1994b). 

The induced state is maintained for about 2 months (in the Cape Province of 

South Africa) and the plant gradually returns to the noninduced vegetative state by early 

spring. Secondary inflorescence buds will abscise when the plant returns to a 

vegetative growth phase. Buds below the secondary inflorescence buds do not develop and 

remain correlatively inhibited, but they will grow out vegetatively if the shoot is cut 

back. A key concept is that the buds entering the bract initiation phase must achieve a 

certain size (characterized as 20 mg DW) or they do not continue to develop (Malan 

1986). Jacobs' (1985) concept that inflorescence initiation was not a response to 

photoperiod, as it does not occur during the long days (LD) of summer and the induced 

state is lost during short days (SD) of winter, changed as evidence mounted for a new 

interpretation. Jacobs' laboratory studied a number of factors, including timing of 

inflorescence initiation; influence of growth regulators, shading, and photoperiod; 

effects of defoliation, decapitation, and other manipulations of the shoots to determine how 

they influenced flowering. 

Jacobs et al. (1986) reported that long days delayed onset of the induced state 

and that flower initiation in Leucospermum required high light intensities during 

vegetative growth followed by SD. The induced state is lost more rapidly under shade

than full sunlight or when the plant is sprayed with GA or ethephon (Napier 1985). 

Napier's studies showed that a decrease in leaf starch was associated with the diminished 

capacity to form flowers. Later work (Malan and Jacobs 1987, 1990) demonstrated that 

LD (3.7 µmol × s -1 × m -2 provided from incandescent lamps throughout the night period) 

could prevent flower initiation on upper axillary buds on shoots decapitated at various 

times from summer through winter, while similarly handled shoots under natural 

daylengths initiated and developed inflorescences. Night break lighting (2 to 6 hr 

depending on length of dark period) was also effective in preventing flowering (Malan and 

Jacobs 1990). 

Since the transition from vegetative to induced state occurred at the same time 

every year, Malan and Jacobs (1987, 1990) suggested that photoperiod might play a 

key role in the induction of Leucospermum. The low level of light energy needed to 

prevent initiation also argued for the participation of photoperiod in the process. Jacobs 

and Minnaar's (1980) observations of simultaneous reproductive development also 

supported the idea of a photoperiod switch. Malan and Jacobs (1990) stated that ‘Red 

Sunset’ was a qualitative SD plant that required at least 42 SD inductive cycles (>12 hr 

dark) for normal flowering. Such conditions prevail at Stellenbosch, South Africa (33°, 

54'S) from April to September. Inflorescence development can occur between May and 

September; however bud responsiveness is weaker after June. 

Leaf removal and shading prevented flower initiation in the interspecific 

hybrid ‘Red Sunset’ (L. cordifolium × L. lineare) (Jacobs 1980). Heavy shading 

applied during summer reduced the number of stems forming an inflorescence (Jacobs 

1983), but long stems were less responsive to the inhibition of flowering at low light 

intensities. 

The question may be posed, "Must a shoot reach a certain size or achieve a 

threshold leaf area, or simply cease elongation to begin to accumulate carbohydrates in 

order to be receptive to an inductive short day?" The appearance of an inflorescence on 

short stems of recent origin following a late pinch argues against shoot age or a 

threshold leaf area as necessary for induction (Jacobs 1980, 1983). Jacobs and Minnaar 

(1980) reported that production of bracts with florets in their axils commenced 

simultaneously on all shoots regardless of variations in the time of shoot growth 

cessation. Cessation of shoot growth on old plants occurred in mid-summer, while 

shoot growth extended into fall on young plants (Jacobs 1985). Jacobs (1985) noted 

that early cessation of shoot growth could also be induced by water stress for plants 

growing under dry land conditions. Malan and Jacobs (1987) stated that buds that had 

developed a number of bract-like leaves would develop as vegetative shoots if the plants 

were stimulated into shoot extension growth by rainfall after growth cessation and 

concluded that shoot growth cessation is not a reliable indicator that the plants had 

reached an induced state for reproductive development. Cessation of shoot elongation 

certainly seems implicated, but the question of whether it is a necessary condition is 

not clear. 

The correlative inhibition of primary inflorescence bud upon secondary 

inflorescence buds was thought due to its IAA production and export (Malan et al. 1994a). 

Diffusable plant growth substances from primary inflorescence buds were collected in agar 

receiver blocks and analyzed by radioimmunoassay and by HPLC. IAA content and its 

export from the primary inflorescence bud did not differ significantly from that of 

inhibited buds nearby, but the developmental patterns favored the primary 

inflorescence. Since all buds exported IAA, they concluded that it was not the IAA 

concentration of a single organ or its inherent ability to export IAA that is responsible for 

inhibition, but the total amount of IAA moving down the shoot that determined the extent of 

inhibition. During floret initiation and differentiation, auxin production and export were 

low, but at the end of the floret initiation stage, IAA and ABA peaked, while GA was 

present until floret initiation was complete, and cytokinins were high in the pre-floret 

stage and first half of the initiation stage, but declined during later stages of 

development (Malan et a1. 1994b,c). GA export peaked just before lateral axillary buds 

35

lost their responsiveness to inductive short days. Since exogenous application of GA also 

reduced the responsiveness of axillary buds to short days (Napier and Jacobs 1989), 

Malan et al. (1994b) proposed that GA export from the primary inflorescence bud was 

responsible for the correlative inhibition of the axillary buds. The GAs could be either GA, 

or GA, or both, as both were detected by the antiserum and had similar polarities and 

HPLC retention times. 

Malan et al. (1994c) determined that benzyladenine (BA) applied to decapitated 

shoots prior to floret development in the secondary inflorescence buds increased the dry 

mass of the inflorescence and number of florets per inflorescence. The results were 

similar to those of Napier et al. (1986a). Extra bracts were initiated on the peduncle, but 

precocious floret development (in these bracts) did not occur and the loss of responsiveness 

to short days in winter time was not affected by the cytokinin compared to untreated buds. 

Malan et al. (1994c) concluded that BA did not interact with the gibberellins that were 

apparently inhibiting lateral bud responsiveness to short days. 

To sum up the role of growth regulating substances in floral development, it 

appears that auxin does not play a major role in inhibiting bud responsiveness to short 

days. Gibberellins from more distal buds, especially the primary inflorescence bud, may 

play the role of correlative inhibitors of lower buds on the shoot. The more developed 

the inflorescence bud, the more strongly the lateral buds are inhibited in 

responding to inductive SD, presumably because of high GA levels (Malan et al. 

1994b). Cytokinins are involved in quantitative roles such as increasing the meristem 

diameter, number of bracts and florets, and number of inflorescences per stem. 

In L. patersonii, LD were required for floret induction, but SD accelerated floret 

initiation (Wallerstein 1989; Wallerstein and Nissim 1988). The LD effect quantitatively 

influenced the number of axillary buds that initiated inflorescences. The most distal 

axillary buds were the most sensitive. Stem thickening was concurrent with the 

cessation of stem elongation under SD, but if the axillary meristems failed to develop into 

inflorescence buds, stem thickening ceased. 

2. Pollination Biology. 

Species of Proteaceae are frequently pollinated by various honey-seeking birds, 

bats, and small animals. The flowers are grouped in capitula consisting of 30-300 

florets. The florets shed pollen over a period of 7 to 14 days, generally before the 

pistil of the same flower is receptive (protandry). Fresh pollen remains viable for up to six 

days when stored at room temperature and up to six weeks when stored at 5°C (Brits and 

van den Berg 1991). The small stigmatic groove (30-300 µm long) opens within 24 hours 

and attains maximum receptivity two to five days after anthesis, as shown in Fig. 2.1 

(Brits and van den Berg 1991). 

Pollen viability can be tested by germinating in 12% sucrose plus 100 mg boron/L 

(Fig. 2.2) (Brits 1992a). Shchori et al. (1992) reported that better germination was achieved 

using Taylor's medium in a hanging drop. 

Ito et al. (1978, 1990) have described their pollination technique. Since 

pollen is shed before the stigma is receptive, emerging styles (hooked stage) are 

gently released from the perianth, and the stigmas are examined for the presence of 

pollen. The anthers are removed from flowers that do not show pollen on the stigma. 

Pollen from fully open flowers of selected male parents is applied to the slotted tip of the 

stigmatic area two days after emasculation and again two days later. The emasculated 

and pollinated flower is covered to prevent contamination and labeled to identify the 

cross. 

36

Fig. 2.1 Average percentage of stigmatic grooves open and number of seed set 

following artificial pollination on successive days after anthesis in 

Leucospermum cordifolium. Source: Brits and van den Berg 1991. 

Fig. 2.2 Effect of sucrose and boron (100 mg H3BO3/L) on pollen germination 

percentage and pollen tube growth in L. cordifolium. Source: Brits 1992a. 

E. Genetics 

Chromosome numbers are constant within the genus at 2n = 24, x= 12 (Rourke 

1972; Van der Merwe 1985). A wide range of interspecific hybrids have been collected 

and introduced to cultivation (Brits and van den Berg 1991). In addition, directed crosses 

are being made among species in efforts to produce later flowering, improve color and 

shape, and introduce tolerance to Phytophthora cinnamomi (Brits 1992a). Brits (1992a) 

noted that self-incompatibility is present to a moderate degree in Leucospermum and that 

interspecific crosses are often highly heterotic. Cross pollination is apparently favored; as 

only 3 to 4% of selfed flowers set seed as compared to 6 to 8% for cross-pollination (Brits 

1992a). Horn (1962) reported even lower percentages of seed set among open pollinated 

37

flower heads. Thus, a strong degree of self-incompatibility and interspecies 

incompatibilities were proposed (Brits and van den Berg 1991). Resources allocation, 

insufficient pollinators, and predation are possible alternative explanations for low seed 

yields. 

III. HORTICULTURE 

The most widely grown Leucospermum species are floriferous, spreading shrubs 

on which relatively short-stemmed inflorescences are borne in the spring. Horticulturists 

have had to develop management practices to improve stem length and straightness for 

their use as cut flowers. Their potential as flowering potted plants was recognized when 

budded cuttings flowered after rooting; stock plants are being manipulated to achieve 

stronger branches for this use. 

38 

A. Propagation 

1. Seed. 

Poor seed (or more properly, achene) germination in Leucospermum has posed 

problems for both horticulturists and plant breeders. Much of the early research to 

overcome this problem has been conducted in the laboratories of Johannes van Staden of 

the Department of Botany, University of Natal. In preliminary studies (Brown and Van 

Staden 1973; Van Staden and Brown 1973), removal of the pericarp and seed coat increased 

germination, as did increasing the oxygen concentration around intact seed. The outer 

layer of the achene (the pericarp proper) becomes gelatinous upon imbibition and is 

presumed to interfere with gaseous exchange. 

Based on a report (Van Staden and Brown 1977) that oxygen promoted embryo 

cytokinin levels, Brits and Van Niekerk (1976) used hydrogen peroxide to improve 

germination. However, the effect was applicable only to proteaceous species with nutlike 

achenes, as 13 out of 15 serotinous species did not respond to the hydrogen peroxide 

treatment (Brits 1986b). Brits (1986c) noted that achenes harvested slightly prematurely 

germinated better than naturally matured achenes and suggested that dormancy was due to 

restricted oxygen uptake attained during the final stages of seed maturation, and that 

dormancy probably resides in the outer layer(s) of the seed coat. 

The hydrogen peroxide treatment was not always successful, which led Brown et 

al. (1986) to examine a range of other treatments successful on seed of other plants. 

Following imbibition, the pericarp was removed, and the seeds were incubated under 

alternating temperatures of 10°C for 8 h and 20°C for 16 h with light (11 W/m) provided 

during the high temperature period from cool white fluorescent lamps. Emergence of 

the radicle was used as the criterion of germination. Germination was on moist filter 

papers to which various growth regulators were added. Some growth regulators were 

supplied as soaks prior to placing the achenes on moist filter paper. Germination 

improved from 11% for controls to 44-50% with GA3 concentrations of 25 to 500 mg/L. With 

the commercial product, Promalin (mixture of GA4, GA7, and benzyladenine), a 24 h soak 

improved germination from 10% for the control to 26 to 46% for Promalin concentrations of 

50 to 400 mg/L. Achenes germinated on filter paper to which a range of ethephon 

concentrations had been added also slightly improved germination over that of the control, 

while incubating achenes in an atmosphere of ethylene gas similarly improved 

germination. In the same series of experiments, hydrogen peroxide (10% v/v) soaks 

improved germination to 24%, compared to 12% for controls. They concluded that the 

gibberellins are the most active group of hormones in stimulating germination of 

Leucospermum achenes and suggested that GA in combination with other treatments 

needed investigation. 

Brits (1986a,c) placed a fluctuating diurnal temperature requirement for 

germination in an ecological context. An optimum high of 24°C and low of 9°C as

determined from controlled experiments -promoted germination. In burnt mesic 

conditions of their natural habitat, Leucospermum seeds germinated during the winter 

when water was most likely to be available, rather than in the warm, dry summer. The 

daily surface temperatures of this sun-warmed soil in winter paralleled those of the 

controlled experiment, while temperature conditions of unburnt, or lightly or heavily 

shaded, soils did not meet the temperature requirements for germination. Brits concluded 

that Leucospermum was closely adapted to its environment with regard to germination 

temperature requirements. He also recorded temperatures at depths of 30 to 45 mm, where 

seeds buried by ants were found. Daily temperature fluctuations during early winter were 

of the same order as the known temperature requirements of L. cordifolium seeds. 

The ecological approach to germination was also evident in a more recent report 

that desiccation, such as that due to fire, breaks the exotesta, and the endotesta as well when 

wetted, to permit oxygen diffusion and hydration of the embryo (Brits et al. 1993). Brits 

et al. (1997) propose that Leucospermum has at least one adaptive strategy for each stress 

or disturbance factor operating in nature: ant dispersal, desiccation-scarification by 

fire, alternating temperature requirement, and ecologically related temperature 

requirements. Phasic changes of gibberellins and cytokinins are also believed to control 

germination through an inductive threshold, mobilization of lipid and protein reserves, 

cotyledon expansion, and radicle growth (Brits et al. 1995). 

Although complicated schema involving sulfuric acid scarification, Promalin (a 

gibberellin + benzyladenine preparation), pure oxygen, and alternating temperatures work 

to improve germination to 95% in the laboratory and are effective on a number of species 

(Brits 1990d), Brits (1991) proposed a simple treatment for commercial seedling 

production. Dry achenes are soaked in a 1% solution of hydrogen peroxide for 24 hours, 

the gelatinous pericarp is removed, and the achenes are sown in open seedbeds in autumn 

when daily temperatures vary from the optimum low at night to the optimum high by day. 

Satisfactory germination percentages (not reported, but presumed from other reports by the 

same author to be about 60%) were the result. This procedure was used successfully for L. 

cuneiforme and L. tottum by Rodriguez-Perez (1993). 

While most propagators agree on the importance of fresh seed for high germination 

percentages, commercial germination practices for proteaceous seed has been subject to 

many variations. Parvin (1974) recommended 3 parts of finely screened cinders to 1 part 

peatmoss as a germination medium with 21°C bottom heat, and "plenty of moisture" 

leaching through 15 cm of medium. Harre (1986) reported his best successes came from 

sowing seed in a 1 loam: 1 pumice mixture or 5 loam: 2 coarse sand: 3 pumice during the 

falling temperatures of autumn, treating with captan to reduce fungal attack, and 

awaiting germination. The hard-shelled seeds of Leucospermum are slow and erratic to 

germinate, taking 3 to 15 months. Harre soaked seed in 60°C hot water for 30 mins prior to 

sowing, but did not clearly state whether this practice improved germination. Perry (1987) 

suggested a hot water soak to minimize seedborne diseases followed by dusting with a 

fungicidal powder. Once seedlings have reached the first true leaf stage, they-are 

hardened off for potting. Harre also advocated ”wrenching”, a technique whereby the 

seedlings are disturbed a week before transplanting to induce lateral root formation. 

The diversity of successful practices does not lend itself to a single recommendation. 

Brits' hydrogen peroxide treatment has broad applicability while Harre's practical 

nurseryman's approach (Harre 1988b) suffices for media, containers, transplanting, 

and environmental considerations. While uneven germination may be the reason that 

growers prefer to transplant rather than direct seed to tubes or pots, improvements in 

seed quality should speed the use of direct seeding in containers suitable for 

transplanting. 

2. Cuttage. 

Leucospermum cutting propagation offers few challenges because most plant 

material roots readily. Brits (1986d) compared terminal and sub-terminal cuttings and 

found that recently matured terminals taken in autumn rooted best. Harre (1988a) 

39

ooted leaf (or possibly a leaf-bud) cuttings of many protea species, but noted that they did 

not produce plants. His observations suggest, however, that leafbud cuttings might be 

examined as a means of rapid increase for new cultivars. However, in other trials, rooting 

and shoot elongation of leaf-bud cuttings were poor, and up to 32 weeks was required for 

transplantable cuttings (Rodriguez-Perez 1992). 

While Leucospermum cuttings can be rooted at almost any physiological stage 

of development, a preferred cutting is the recently matured new growth, known as a 

semi-hardwood cutting (Malan 1992). This type of material is gathered in autumn 

after shoot growth terminates. Harre (1988a) recommended removing the tip about a 

week before taking the cutting because rooting was improved, and vegetative growth 

resumed readily following rooting. Manipulation of cuttings on the stock plants before 

harvest as well as after the collection of cuttings was suggested as a means to improve 

rooting (Harre 1989). Cuttings (type and maturity not specified) of L. cordifolium 

‘Riverlea’ were harvested fully turgid in early morning and held under mist for varying 

periods before being treated with 2000 ppm IBA and placed under automatic mist 

(cycle not given). Delays of 3 and 5 days before sticking the cuttings yielded rooting 

in excess of 90%, while a delay of 7 days reduced rooting to 77%. The cuttings were 

deemed well enough rooted that hardening could begin after 44 days and potting up after 

50 days. 

Another aspect to manipulating the future cutting was developed for the production 

of potted Leucospermum plants (Brits et al. 1992). Well-branched cuttings induced by 

spraying a primary elongating shoot with 960 mg/L ethephon rooted easily in 6 to 8 weeks. 

Yoshimoto (1982) proposed that air-layering of branched cuttings was another technique 

that could be used to produce larger plants for pots or for field planting. 

As a result of practical experiments, Harre suggested that rooting under 35- 

50% shade is superior to lower light intensities; that a well-aerated medium leads to 

superior root quality (his examples included better rooting in cracked tubes and tubes 

with holes and when cuttings were placed down the side of a tube); and that initial 

propagation under automated intermittent mist, then shifting onto capillary watering beds 

as roots initiate, provided excellent results (Harre 1988a, 1989). Cuttings from wellnurtured 

stock plants 2 to 5 years old are his preferred propagules. He also recommends 

pinching and cutting back the stock plants to yield more cuttings of a uniform diameter 

and quality. 

Rooting Compounds. While Leucospermum cuttings often root without the aid of auxins, 

most nurseries use auxin treatment to enhance rooting. Rousseau's early report (1968) 

suggested IBA solutions of 0.2 to 0.4% were adequate and mixtures of IBA/NAA in the 

same range gave about the same results. McKenzie (1973) used a.quick dip in 0.3% IBA, 

noting the results were better than with Seradix No. 2 powder. A range of 0.2-0.3% IBA 

was recommended by Parvin (1974), while Parvin (1982) later reported improved 

rooting of two South African Leucospermum hybrids over untreated controls when liquid 

IBA-NAA (2:1) formulations were used, and total auxin concentrations were in the 

range of 1300 (1:10 dilution) to 2500 (1:5 dilution) parts per million. A talc dust of 0.8% 

IBA (as Hormex #8) yielded somewhat lower rooting percentages than did the liquid 

formulations, while Yoshimoto (1982) recommended 0.65% IBA in talc powder. Jacobs 

and Steenkamp (1976) reported on the results of a series of IBA treatments (from 0 to 8000 

ppm) and recommended 4000 ppm as either a quick dip solution or talc dust for L. 

cordifolium semi-hardwood cuttings. Asper (1984) routinely used 5000 ppm IBA as a dip 

treatment to induce rooting. 

Propagation Medium and Bottom Heat. Rousseau (1968) used a sandpeat mixture for 

rooting, while Yoshimoto (1982) found a 1 peat: 2 perlite medium produced the best 

results. Interestingly, Harre (1988a,b) avoids peatmoss in his post-rooting medium and 

instead includes scoria, sand, or pumice with soil. He suggests that proteoid roots, 

which develop in the peat-based medium, do not contribute to the establishment of 

liners when they are transplanted to the field. A lengthy exchange of opinions 

40

concerning the use of peat or bark suggested there was no good biological basis for 

avoiding peat, as many proteaceous plants were grown well in media containing peat 

(Blake 1987). For example, McKenzie (1973) used a 1 peat: l sand medium for 

propagation and 2 soil: l peat: l sand as a potting mix. Jacobs and Steenkamp (1976) 

evaluated several rooting media for L. cordifolium and recommended a 2:1 or 1:1 

mixture of peat and polystyrene grains over mixtures of 2:1, 1:1, or 1:2 peat and sand, 

because the former clung to the new roots better than did the heavier sand-based medium. 

Brits (1986d) reported that bottom heat (23 ± 0.8°G) greatly improved rooting over 

no bottom heat (12 ± 2°C) under mist, and that the use of IBA-based rooting compounds 

improved rooting at the cooler temperature but not at the warmer. Cultivar differences 

were important, with 75% rooting for ‘Caroline’ and only 30% for ‘Hybrid T 75 11 24’. 

Sub-terminal cuttings did not root as well as terminal cuttings of the same cultivar given 

bottom heat, but were nearly equal to or outperformed terminal cuttings without bottom 

heat. Brits also observed that misting at long intervals, and allowing the leaves to dry off 

between on cycles did not influence cutting mortality, perhaps because the xerophytic 

character of Leucospermum may impart some tolerance to drier rooting conditions. These 

results suggest the potential to develop simpler, cheaper, and healthier rooting 

technology than conventional frequent-misting systems (Brits 1986d). 

3. Grafting. 

Grafting is often viewed as a solution to problems of root system adaptation to low or 

high pH soils, salinity, or soil-borne diseases. Grafting on lime-tolerant rootstocks has 

been recommended as an approach to problems of protea production on soils of neutral to 

slightly basic pH (Brits 1984b). A lime-tolerant species such as L. patersonii was 

recommended. Moffat and Turnbull (1993) evaluated rootstocks resistant to 

Phytophthora cinnamomi, and although none were found in the genus Leucospermum, 

they found a variety of grafting techniques that worked well on either rooted cuttings or 

on cuttings to be rooted under mist (cutting grafts). 

The standard grafting technique is wedge-grafting of leafy semi-hardwood 

scions onto seedling rootstocks (Rousseau 1966; Vogts et al. 1976), but the requirement 

of a mist system during wound healing increased costs and stimulated a look at other 

techniques. Approach grafts are also successful but more time-consuming to execute, 

and required more aftercare. 

During 1976 to 1980, G. J. Brits of the Vegetable and Ornamental Plant 

Research Institute (Riversonderend, South Africa) conducted 40 grafting and budding 

experiments to determine rootstock production methods, grafting and budding techniques, 

potential understocks, and to evaluate the effectiveness of grafting (Brits 1990b, 1990c). 

Rooted cuttings of Leucospermum were superior to seedling rootstocks because of 

necessary thickness requirements, uniformity, and clonal selection possibilities. The 

wedge graft, using a 2-bud scion with 0.5 cm 2 leaf blade subtending each bud, yielded 80 

to 95% take on rooted cuttings, while chip budding onto unrooted cuttings yielded a 93% 

success rate. Prior to planting out in the field, the scion should be allowed to produce at 

least 5-cm-long shoots in the nursery. As to time of year, Brits expressed a preference for 

early autumn, although he noted that grafts made in the spring had the benefit of 

producing growth during the same growing season. 

The use of cutting grafts, where the graft union develops while the cutting roots, is 

also recommended (Brits 1990b). Cutting grafts were evaluated using four Leucospermum 

cultivars (Ackerman et a1. 1995). In the second year after planting established liners into 

the field, the grafted plants significantly out-yielded the same cultivars on their own 

roots. Ackerman and his colleagues concluded that there was significant advantage to 

using resistant rootstocks selected for their suitability to the local soil types. Brits (1995b) 

reported that budding onto a cutting and rooting it was more economical than grafting. 

The choice of rootstock was important, because 'Vlam' roots with difficulty while 

hybrid rootstocks could be selected with 100% capacity to root (Brits 1990b). Brits 

(1990c) evaluated 19 Leucospermum species with rootstock potential and found great 

41

variability in capacities to root as cuttings, support vigorous scion growth when used as 

rootstocks, and produce a shoot of graftable diameter (Table 2.3). None of the species 

exhibited great tolerance to Phytophthora cinnamomi, although a hybrid of L. formosum 

× L. tottum designated as ‘T75 11 02,’ and another of L. conocarpodendron ssp. 

viridum × L. cuneiforme, designated ‘T75 11 24’, performed well in one field 

experiment. 

Selection of rootstock plays a significant role in improving adaptability and 

yield of Leucospermum. Van der Merwe (1985, and references cited therein) produced 

a number of intergeneric grafts, and suggested close genetic relationships as a result 

of compatibilities he found. One important result was that Serruria may be grafted onto 

Leucospermum conocarpodendron and grown in sites where Serruria on its own roots 

would not survive. Malan (1990) compared an interspecific hybrid (L. tottum × L. 

formosum) and ‘Sue Ellen’ understocks for cuttings wedge-grafted with scions of ‘Sue 

Ellen’ (a hybrid of L. cordifolium × L. lineare). While graft union rates were only 12.2% 

and 23.8% for ‘Sue Ellen’ on itself and the hybrid, respectively, due to the inexperience of 

the laborers, rooting was faster for the hybrid understock cuttings and growth of the scion 

shoots was better than for the ‘Sue Ellen’ understock cuttings. Malan also noted that new 

growth of ‘Sue Ellen’ scions was less affected by Phytophthora cinnamomi root rot when 

grafted on the hybrid than on its own roots. Brits (1995b) reported that budding onto 

‘Spider’ cuttings in the fall, followed, by LD during winter, produced market-ready 

plants six months later. Moffat and Turnbull (1994) recommended additional investigation 

of L. saxosum as a potential rootstock with low susceptibility to Phytophthora. Root rot 

resistant understocks have the potential to increase plantings of Leucospermum where 

Phytophthora root rot is a problem. 

4. Tissue Culture. 

Leucospermum cordifolium callus culture without organogenesis was reported 

by Van Staden and Bornman (1976). Ben-Jaacov and Jacobs (1986) reported success in 

bud sprouting from semi-hardwood shoot segments of ‘Red Sunset’, an interspecific 

hybrid of L. cordifolium × L. lineare, on filter paper bridges immersed in liquid 

Anderson medium with 2 ppm BA. Kunisaki (1989, 1990) achieved proliferation from 

axillary bud explants in half-strength MS inorganic salts, 2% sucrose and 0.2 mg BA per 

liter. Round, green proliferating bodies were induced to form shoots after transfer to filter 

paper bridges. After 4 to 6 leaves developed, the propagules with their shoots were 

transferred to agar medium, then, at 5 to 10 mm in height, they were separated from the 

propagules and grown on to greater length. Rooting was achieved by soaking the basal 2 

to 4 mm stem in 50 or 100 mg IBA/L solutions for 4 days (later modified to a 10-min dip 

in 150 mg IBA/L). The microcuttings were rooted in an agar-based half-strength MS 

medium with activated charcoal and 2% sucrose. Kunisaki (1990) reported greater 

success with a modified composition of the agar rooting medium, but also noted that 

rooting could be achieved in sterile perlite. A “feeder leaf” technique was employed 

successfully by Rugge et al. (1990), in which a leaf blade on an explant was inserted into 

the culture medium. Axillary bud sprouting above the feeder leaf was substantially 

improved over the bud subtended by the feeder leaf or buds proximal to the feeder leaf 

in this technique. 

42

Table 2.3. General characteristics of 19 Leucospermum species with rootstock potential for species of the section Brevifilamentum 

Rourke, determined from horticultural data or deduced from ecological data. Source: Rourke 1972. 

Horticultural Data Ecological Tolerance 

Graft 

compatib 

Leucospermum sp. ility Rooting 

Vigor of Plant 

rooted size/stem 

pH 6.5- Rel. high 

ability cuttings diameter Longevity 8.5 salts Drought Cold Wet soils 

catherinae (B) 61 C C C C C D B A 

Conocarpodendron ssp. 

Conocarpodendron ssp. B 71 D A A B B B C C 

Viridum (Durbanville) B (70) D A A B B C C C 

cordifolium A 100 C C C C C C C C 

cuneiforme (C) 50 C C B C C B C C 

erubescens (C) (60) C C C C C B C C 

formosum B 56 B B B C C D C B 

fulgens (B) 78 C B A B C D C 

gmndiflorum (B) 66 B C B B B C C 

guenzii (B) (60) C B B B B D C B 

patersonii A (100) A A A A B C D C 

p/uridens B 14 C B A B B B B C 

proecox (B) 100 B B B A B C C C 

pmemorsum (B) 56 B A A C C B B C 

reflexum C (66) B B B C C C A B 

rodolentum (C) 51 C C C A B C C C 

saxosum (C) (60) D D D B B C B C 

truncatum (C) 61 D D C A B C D C 

utriculosum (C) 29 C C C C C B C C 

vestitum (A) 42 C C C C C B C C 

Real or expected compatibility is based on grafting results with 6 exceptional candidates and on taxonomic relationships, respectively. 

A = excellent; B = good; C = average/normal; D = unsatisfactory relative to L. cordifolium. Rooting values (except those in 

parentheses) ex Jacobs 1982 (Brits 1990c).

Tal et al. (1992a) showed that cytokinins and GA3 had strong effects on 

multiplication, but that a medium containing BA was better than zeatin. GA3 at 1 to 2 

mg/L was essential for rapid proliferation and elongation of the shoots, providing nearly 

double the shoot increase of BA alone. GA3 also enhanced shoot length, an important 

consideration in handling shoots during subculturing. Light intensities of the level of 230 

µmol × m -2 × s -1 enhanced in vivo rooting compared to lower intensities. The auxins, 

IAA, IBA, and NAA, all improved rooting over the use of no auxin, but the best 

rooting was with 1 mg IBA/L. Hardening off was successfully accomplished using plantlets 

with 3 to 5 nodes, fog (delivering 0.25 mm water/h), and high levels of light (14,000 

lux). In conclusion, research results have laid the groundwork for commercial 

micropropagation of Leucospermum, but conventional systems of vegetative 

propagation are more widely used. 

44 

B. Environmental Responses 

1. Light. 

Jacobs and Minnaar (1980) determined that light intensity reductions of up to 

50% did not slow the rate of flower development, but flower quality, as assessed by the 

number of styles per flower head, receptacle length and diameter, and inflorescence dry 

weight, decreased with decreasing light intensity. Jacobs (1983) proposed that there was 

a quantitative response to light intensity because heavy shading prevented flower 

initiation. Napier (1985) found that shading plants when they had been induced led to 

reduced carbohydrate in the leaves and a loss of the induced state. The reduced capacity 

of deheaded shoots to initiate an inflorescence during winter may be more related to low 

light energy relationships than to a short photoperiod (Jacobs 1980). Jacobs and Minnaar 

(1980) ruled out a major role for light intensity and stated that the main factors affecting 

rate of flower development in pincushion were temperature and shoot size. 

2. Temperature. 

In the areas of South Africa where Leucospermum spp. are native, the mean 

annual temperatures are 13 to 16°C and the monthly mean is below 20°C (Ben-Jaacov 

1986). Leucospermums are frost-sensitive, and growers have observed plant loss in 

severe frosts. Diverse protea-growing areas such as Israel, western Australia, and 

California achieve greater extremes (Ben-Jaacov 1986). In the commercial production 

area of Hawaii, the range is from a monthly minimum daily mean of about 13°C during 

winter to a maximum daily mean of 25°C in late summer, but the daily mean seldom 

exceeds 20°C. The protea-producing area of the island of Madeira at 500 m above sea level 

has winter/summer ranges of 10-18/15-25 ° C (Blandy 1996). 

Prior to establishing that flowering was under photoperiodic control, Jacobs (1976) 

and Jacobs and Honeyborne (1979) proposed that the accumulation of heat units (from 

4.4°C to the average daily temperature beginning 1 May onwards in South Africa) 

controlled the rate of floral development. Following removal of a primary inflorescence 

bud, about 925 heat units above a 5.8°C base temperature were required to mature 90% of 

secondary flower buds that began to develop. Fewer days were required in late spring than 

early spring as a response to greater heat unit sums per day, about 8.5 early on to about 

20 by mid-summer. Jacobs (1976) also suggested that the exploitation of warm and 

cool growing regions could extend the production period from August into January. 

Criley et al. (1990) reported a 120-day development period for inflorescences of 

‘Vlam’ once floret initiation began in the fall, with about one-fourth of the heat units 

accumulated in the last month of development. Heat unit accumulation (from a base of 6°C 

to the mean daily temperature from 1 September) was uneven, varying from 14 units/day 

in mid-fall to 10 in mid-winter under Hawaii conditions, with an average of 12.8 heat units 

per day over the period of development. The heat unit total was 1536 units from floret 

initiation until 50% bloom was achieved. They concluded that under short photoperiods 

with high light intensities, floral development could be rapid if temperatures were not

limiting. 

Application of the light and temperature results may be difficult to achieve for 

field-grown pincushion plants, but possibilities exist for potted plants. One scenario 

would impose 12 hr SD during the high light period of the year on potted plants grown at 

18-20°C. Flowering could be expected about 4 months after the development of a 1 cm 

bud. 

3. Cold Tolerance. 

In South Africa, most Leucospermum species are indigenous to frost-free areas of 

the Cape (Ackerman 1995) (Table 2.4). When grown outside their natural habitats, they 

experience both warmer and cooler temperatures. As a general statement, they will 

tolerate brief exposure to temperatures as low as -3°C. L. cordifolium is affected by 

severe frost, while species from higher elevations, such as L. tottum and L. vestitum, are 

more cold tolerant (Vogts 1980). L. lineare, from elevations of 300 to 1000 m, is another 

cold-tolerant species. Research on cold acclimation has not been reported, but growers 

have shared knowledge about plant survival during episodic cold periods through the 

newsletter of the IPA. 

4. Soils. 

Most of the Leucospermums are indigenous to nutrient-poor, coarse, acidic, 

sandstone-derived soils. A few species are indigenous to soils derived from limestone 

and with a high pH. Vogts (1980) and Matthews and Carter (1993) have described the 

native locales of several important commercial species, including L. cordifolium, L. 

vestitum, and L. tottum. The weathered Table Mountain sandstone soils (pH 4.5 to 6.5) of 

the Caledon and Bredasdorp districts support populations of L. cordifolium, while L. 

vestitum is found on similarly acidic soils in mountainous areas of the West Cape north 

to the Cedarsburg range. Weathered sandstone soils support L. tottum in mountainous areas 

of the Cape. L. lineare is found on gravelly clay soils derived from granite in mountains 

of the southern Cape. 

The Leucospermums seem adaptable to a variety of soil types within a narrow 

range of pH and fertility levels, as evidenced by their culture in Hawaii and the Canary 

Islands (volcanic soils), southern California and Israel, Australia, and several regions of 

southern Africa. Soilless culture has also been successful using either 10 cm slabs of 

rockwool or crushed volcanic rock (Calo 1986). 

Table 2.4. Origin and altitudinal distribution of some of the Leucospermum species grown 

in commercial cultivation (Rebelo 1995). 

Leucospermum sp. Habitat Elevation (m) 

Conocarpodendron ssp. 

Granite and sandstone soils 

conocarpodendron 

to 160 

cordifolium Sandstone soils 30 to 500 

glabrum Cool, southern slopes on peaty soils 150 to 500 

lineare Granite-derived clays 300 to 1000 

patersonii Restricted to limestone soils 50 to 300 

reflexum Near streams on sandstone soils 1000 to 2000 

tottum var. tottum Sandstone slopes 300 to 2000 

vestitum Varied, on rocky sandstone slopes 60 to 1350 

45

46 

C. Cultural Practices 

1. Spacing. 

Planting densities are governed by two considerations: the ultimate size of the 

plant and the method of maintenance. One commercial grower recommended that 

Leucospermum be planted 3 m apart in rows (Matthews 1982). An Australian 

recommendation is 1.7 m in-row and 3.5 m between rows (Matthews and Matthews 

1994). A South African grower reported a spacing of 1.75 × 0.75 m (7580 plants/ha), but 

planting distances would change with changes in pruning method (Steenkamp 1993). 

As good drainage is required, hardpan should be broken up and the soil rototilled. If posts 

and wire supports are used, the height of the lowest wire will depend on the size of bush 

being planted, but may be as low as 15 cm from the ground. Additional wires are 

installed later. The main leaders of the plants are fastened to the wire by clips of the 

type used in the culture of various vining fruits. 

2. Pruning. 

Management of proteas began with minimal attention to the plant structure. 

However, as with many other woody plants, pruning was found beneficial because heading 

back increased lateral shoot production and controlled plant height and shape for ease of 

harvest and to facilitate spraying. Brits et al. (1986) pointed out that a balance between 

thinning and heading back is necessary to stimulate vegetative growth while minimizing 

production of non-marketable short flowering branches. 

Brits et al. (1986) distinguished between proteas with a lignotuber and ordinary 

non-lignotuberous species. Some Leucospermum species (L. saxosum, L. 

cuneiforme) are lignotuberous, which means they produce an enlarged base consisting 

of thickened wood and bark on which numerous axillary and adventitious buds are 

visible. The lignotuber provides a source of new shoots when veld fires damage the 

higher parts of the plant. Both fire and pruning down to the lignotuber serve to rejuvenate 

the plant. In contrast, older shoots of the non-lignotuberous species tend to die back to the 

base, and pruning is used to remove old, nonproductive shoots or to stimulate lateral 

breaks on young (1- or 2-year-old) wood. 

Leucospermum is pruned differently from Protea (Brits et al. 1986; Matthews 

and Matthews 1994) (Fig. 2.3). Strong flowering branches of the current season are 

headed back to 7-15 cm during or soon after flower harvest to produce bearing branches 

for the ensuing season. The early cutback permits a longer growing season and, 

potentially, a longer stem. Thinner, later-flowering branches are cut to their origins, as 

new shoots that might sprout from a short, thin stub result in a cycle of short branches, 

which again produce short branches. Producers normally thin the non-marketable 

flowering branches in a separate operation at the end of the flowering season. Strong 

flowering branches of lignotuberous species are headed back to within 30 cm of the base 

of the plant at a point just above well-developed buds. 

Other aspects of pruning of Leucospermum parallel practices followed in 

managing other woody plants (Brits et a1. 1986). Old flower heads and seed heads are 

removed during postharvest follow-up pruning. Vigorous shoots of 10 to 15 cm length 

that developed during flowering are allowed to remain. Young, actively growing 

dominant shoots should be pruned back to 20 to 40 cm. poorly branching and short, thin 

shoots and dead and diseased shoots are removed. Seedling plants and rooted terminal 

cuttings of Leucospermum are headed back during vegetative growth flushes to improve 

plant shape and remove horizontal branches lying on the ground (Matthews and Matthews 

1994). Flower heads that form on rooted cuttings should be removed to encourage lateral 

shoot growth. The prevalence of disease in the aerial portions of the plant will dictate the 

use of disinfectant on the pruning shears and protective sealants on pruning wounds 1.5 

cm diameter or greater. Matthews and Matthews (1994) distinguish between L. 

cordifolium and other species of Leucospermum in recommending that the number of 

flowers per bush of the cordifolium types be strictly limited by pruning during the early 

years of bush development to achieve a more upright bush habit and longer stems. Yr 1: 0

Plate 1 Banksia serrata painted by Celia Rosser. Courtesy of Monash University. 

Leucospermum cordifolium ‘Vlam’ 

Plate 2 Leucospermum species that have contributed to the commercial assortment of 

pincushion cut flowers or potted plants (L. oleifolum). Photos by P.E. Parvin and R. A. 

Criley. (Continues on next page)

Leucospermum tottum 

Leucospermurn conocarpodendron subsp. conocarpodendron 

Leucospermurn lineare 




Leucospermum vestitum 

Leucospermum oleifolum 

Leucospermum patersonii 




Leucospermum reflexum var. luteum Leucospermum reflexum 

Leucospermum glabrum 



Criley.

Flw; Yr 2: 4 Flw; Yr 3: 10 Flw; Yr 4: 25 Flw; Yr 5: 50 Flw; Yr 6: 60 Flw. In their 

program, pruning is done at flowering and for a month or so afterwards. 

Fig. 2.3 Schematic representation f four types of schoots borne on productive 

Leucospermum plants and suitable pruning sites. A: strong flowering branch, the 

base of which is left when the flower is cut; B: weak flowering branch of 

marketable length; C: Weak, non-marketable flowering branch-both B and C are 

cut flush with the parent branch thinning cuts); D: thin, vegetative schoot that is 

left to develop in another growing season. b= flower; M= parent branch. Source: 

Brits et al. 1986. 

Pruning is also used to influence flowering, principally to delay it. Early fall 

pruning to leave 10 to 15 shoots of 10 to 15 cm length was evaluated by Malan and 

Jacobs (1994) as a means to delay flowering through the production of shoots 

physiologically incapable of responding to short day inductive conditions. Night break 

lighting between 20:00 and 04:00 and supplemental irrigation were additive in prolonging 

stem growth. Naturally short day-lengths in spring were expected to result in reproductive 

development and an extended flowering season. The system was unsuccessful, however, 

because changes in growth habit during the cool, reduced-light-intensity days of winter 

resulted in few marketable stems. This study should be repeated, however, with other 

cultivars or in warmer regions to determine if temperature or light intensity were truly 

limiting. 

3. Disbudding. 

Following up on work by Jacobs and Honeyborne (1978), Brits (1986e) and Jacobs et 

al. (1986) demonstrated that removal of the primary inflorescence bud about two months 

prior to normal flowering led to the development of secondary inflorescence buds and a 

later harvest. Brits (1977) had previously demonstrated that application of ethephon to the 

branches prevented development of the primary inflorescence and activated the 

secondary inflorescence buds; later flowering was the result. Timing, however, was 

important, as late treatments caused loss of yield and decreased flower quality. Brits (1986e) 

suggested that it was necessary to select cultivars that would respond favorably to 

deheading or ethephon treatments. Both normally flowering and late-flowering cultivars 

were responsive. 

Although all buds on a shoot have a potential to develop as flowers, normally the 

first bud to develop inhibits reproductive development of other buds. In a few species such 

47

as L. erubescens and L. saxosum more than one flower develops, but on most largeflowered 

species, this is uncommon and undesirable for packing and shipping. Malan and 

Roux (1997) note that the characteristic of producing multiple flower buds does permit 

extension of the production season by removing the primary bud and allowing a secondary 

bud to develop. Since the second bud was suppressed in its initial development, it 

flowers later (Jacobs 1983, 1985). Malan and Jacobs (1990) had previously observed 

that decapitation of the terminal 5 cm of a growing shoot caused axillary bud break that 

was vegetative during natural or artificial long days but that resulted in development of an 

inflorescence in the uppermost axillary bud during the shorter day-lengths of fall. The 

capacity of these axillary buds to develop as inflorescences was lost as days lengthened 

in the spring. Between 42 and 56 SD cycles were necessary for inflorescence 

development and late winter decapitation provided too few SD for reproductive 

development. 

Cultivar differences exist in the responsiveness of axillary buds to develop as 

inflorescences (Jacobs and Honeyborne 1978; Jacobs 1980, 1983). Disbudding of the 

primary inflorescence of ‘Golden Star’ in South Africa as late as October 15 was possible 

without crop loss (Jacobs and Honeyborne 1978), but ‘Red Sunset’ buds regenerated as 

vegetative shoots. September 15 was considered as the latest date at which disbudding 

would still provide a crop. Malan and Roux (1997) stated that the flowering time of 

early-flowering cultivars such as ‘Ballerina’ and ‘Starlight’ could be delayed better 

using disbudding techniques than later-flowering cultivars (Table 2.5). 

The disbudding operation is more complex than merely delaying flower 

production because it impacts upon the next year's crop as well. Malan and Roux (1997) 

caution that the most vigorous shoots should not be disbudded, as these will be the early 

harvest of flowers and from their stubs develop the shoots for the next season's crop. 

Shoots of average vigor may be disbudded to produce a late crop, while weak shoots (

Table 2.5. The period of delay from normal peak flowering time, at Elsenburg, South Africa, following disbudding of Leucospermum 

cultivars during the period indicated (Malan and Roux 1997). 

Disbudding Period 

Normal Late April Late May Late June Late July Late August 

Cultivar flowering Weeks delay 

Tested on most vigorous shoots (mostly 60 to 80 cm long) 

Sunrise late July 3-4 7-8 13-14 16-17 16-17 

Luteum early Sept. 3 month distribution 

of disbudded shoots 

Gold Dust early Sept. 2-3 4-5 6-7 8-10 11-12 

Scarlet Ribbons mid Sept. 0 1-2 3-4 5-6 6-10 

Flamespike mid Sept. 0 0-1 0-2 4 6-7 

Helderfontein late Sept. 0 2-4 6-7 - - 

Yellowbird late Sept. 0 0-1 1-2 4-6 4-8 

Ballerina early Oct. 0 0-3 2-4 4-7 7-11 

Caroline early Oct. 0 0-1 0-2 1-4 4-7 

Red Sunset early Oct. 0 0 0-3 3-4 4-7 

Gold Star mid Oct. 0 0 0 0-3 2-6 

Vlam late Oct. 0 0 0-1 2 5-7 

Goldie late Oct. 0 0 0-1 0-1 

Tested on average shoots (40 to 60 cm long) 

Succession I early Sept. 4-5 4-5 5-7 5-8 

Succession II early Oct. 0-1 1-4 4-6 5-7 

High Gold early Oct. 1-3 3-5 5-6 8-10 

Starlight early Nov. 0-2 1-4 1-7 3-8

4. Irrigation. 

Water requirements for most Proteaceae have not been determined. In the 

mountainous regions of the Cape where many Leucospermum species are found, rainfall 

(@ 400 to 1000 mm) is concentrated in the winter months, while a few species are found in 

the summer rainfall (600 to 1000 mm) regions inland and further north. In the western 

Cape province, pincushions are cultivated without supplemental irrigation, relying on 

natural winter rainfall of 600 to 700 mm. 

Malan and Jacobs (1994) reported that shoot growth cessation could be prevented 

during the dry fall by weekly irrigation at the rate of 27 L/mz (calculated from the 

author's description of their methodology), but night break lighting was required to continue 

the effect through winter. They concluded that water stress was the main cause of 

cessation of shoot growth prior to inductive SD in the autumn. However, many 

shoots were incapable of uninterrupted apical growth, and the development of distal 

axillary shoots rendered the shoots unmarketable as flower stems. Winter shoot 

production through the use of night break lighting and irrigation was not an effective 

approach to delay flowering until summer in ‘Red Sunset’ pincushion. 

In a typic eutrandept, medial isothermic soil, commonly denoted as a loam at the 

Maui Agricultural Research Station (Kula, island of Maui, Hawaii, USA), where an 

average annual rainfall of 45 to 100 cm rainfall occurs, an irrigation rate of 5.5 to 7.5 L per 

plant per day was determined optimum (Wu et al. 1978). Less water was used in 

fumigated fields where the stress of root-knot nematodes was absent. The presence of 

root-knot nematodes increased water requirements by nearly 2 L per day. A rate of 3.8 L per 

day could achieve 80% of optimum yield during drought situations. The latter rate is 

similar to Malan and Jacobs (1994) rate of 27 L/mz, but is less than the 35 L per week 

recommendation of Furuta (1983). 

5. Nutrition and Fertilization. 

Unique to the Proteaceae are clusters of finely branched even-length rootlets 

occurring throughout the shallow root system of most species (Purnell 1960). The 

rootlets are crowded together along the axis of the lateral roots and are covered with long 

root hairs. They do not appear to have mycorrhizal associations, but it is reported that 

they are microbially induced (Malajczuk and Bowen 1974). The masses have a 

lifespan of about 6 months before shrivelling and disappearing. Such root masses are 

known as proteoid roots, and through their large surface areas they are thought to be 

responsible for K and P absorption (Lamont 1986; Vorster and Jooste 1986a). Grierson and 

Attiwill (1989) found increased H+ ion concentrations in leachates of proteoid roots, but 

also found increased levels of reduced manganese, and suggested that unidentified 

chelating compounds were released as well, since high amounts of aluminum have 

been found in leaves of Proteaceae. Lamont (1986) cautions that management practices 

such as cultivation will damage proteoid roots, and weed control is essential to reduce 

competition between the shallow proteoid roots and shallow-rooted weeds. Since the 

proteoid roots are concentrated in the leaf litter and surface layers of the soil, proteaceous 

species tend to be sensitive to chemical treatments, whether they be fertilizer, 

nematicides, or fungicides. 

Phosphorus absorption in proteoid roots of Protea compacta showed a peak between 

pH 4 and 5.5 (Vorster and Jooste 1986a). Analyses also showed that proteoid roots were 

more effective in absorbing potassium than were ordinary roots. However, proteoid 

roots also accumulated their P, acting as sinks, while ordinary roots readily translocated P 

to the aerial parts (Vorster and Jooste 1986b). Inclusion of sucrose in experimental 

solutions stimulated the translocation of P from the proteoid roots, suggesting an energydependent 

mechanism for translocation from proteoid roots to the aerial parts. Proteoid roots 

were metabolically more active in P absorption at 35°C than at lower temperatures, while 

ordinary roots increased their rate of P absorption over the range of 15 to 35°C (Smith 

and Jooste 1986). Proteoid roots also displayed a higher oxygen uptake than did ordinary 

50

oots. Grierson and Attiwill (1989) demonstrated that proteoid roots can acidify their 

immediate environment. pH values of 4.2 to 4.4 were reported in the leachates of 

proteoid roots of Banksia integrifolia, while associated leaf litter and soil 5 cm away 

had pH values of 7.1 and 5.5 to 6.5, respectively. They concluded that nutrient uptake is 

enhanced by lower pH and the release of organic chelating compounds from the roots. With 

Protea cynaroides, periods of active growth of proteoid roots immediately precede bud 

differentiation and bud development (Hanekom et a1. 1973) and thus correlate with 

periods requiring high nutrient uptake. 

Although the above results were obtained with Protea compacta, P. cynaroides, 

and Banksia integrifolia, the principles may be extended to Leucospermum. The mass of 

fine proteoid roots permits greater diffusion of oxygen around them. Their sugar and oxygen 

requirements and greater metabolic activity in both ion absorption and translocation suggest 

proteoid roots play a unique role in the nutritional status of these plants. The proteoid roots 

die off during the dry summers and are replaced each winter with the return of winter rains, 

a period when inflorescence development takes place. 

Both numbers and mass of proteoid roots increased during L. parile seedling 

development (Jongens-Roberts and Mitchell 1986). Mobilization of P to the canopy 

occurred in 1- to 2-year-old plants, while in 5- to 6-year-old flowering plants, P level 

declined in the non-reproductive parts of the plant. In young plants, root production and foliar 

phosphorus content increased during the winter, but there was a marked decline in both in older 

plants. 

The phosphorus-phobia vis-à-vis the Proteaceae is widely circulated in the 

commercial literature [c.f., "Provided phosphate is totally withheld, average pH levels of 5 

will be acceptable..." (Riverlea Nursery undated)] and has received attention from 

researchers (Allemand et al. 1995; Malan 1996). Rates of fertilization considered normal 

for other woody plants often caused phytotoxicity to proteas, and Munro (1990) related that 

growers were advised not to supply P in their fertilizer programs. Nichols (1981) classified L. 

cordifolium among the highly sensitive proteas as a result of experiments providing young 

plants with 1 to 2 kg P/M3 of soilless potting medium. Sanford (1978) reported very little 

effect of phosphorus addition (as treble superphosphate) of up to 400 kg P/ha in field culture, 

although there was a slight increase in marketable yield. Foliar content of P was not 

correlated with yields of flowers per plant. One Australian grower (Bowden 1987), however, 

reported that his proteaceous plants responded to low levels of slow-release forms of P. His 

account suggests a need to examine the form in which P is applied. Trials of 0.1% potassium 

dihydrogen phosphite as a foliar spray for Phytophthora cinnamomi control showed no 

trace of phytotoxicity in several proteaceous species, including L. reflexum, while 

providing a high degree of control of the pathogen (Wood 1987; Turnbull and Crees 1995). 

Similar effectiveness was observed on four Leucadendron species (Marks and Smith 1989). 

Matthews (1982) suggested that soils used for Leucospermum culture should have a pH 

of 5 to 5.5, K and P levels below 20, Ca below 10, and Mg below 30. On the basis of New 

Zealand Ministry of Agriculture and Forestry soil analysis, the following nutrients levels 

(units not specified) were considered suitable for Proteaceae: Ca, 6; P, 4 to 6; K, 4 to 6; and 

Mg, 8 to 12 (Salinger 1985). In Hawaii, a minimum soil content of 32 ppm (P205), 

0.117 meq K, and a pH of 5.5 to 6.1 were recommended (Munro 1990). 

In soilless culture using rockwool slabs or crushed volcanic rock, satisfactory 

growth of L. tottum and L. reflexum was achieved using a fertility regime of 50 ppm N, 

15 ppm P, 25 ppm K, and 1 ppm microelements. The pH was maintained between 5.5 and 

6.5 by addition of sulfuric acid (Calo 1986). In pine bark and sand, root development, 

plant height, and branching of containerized L. cordifolium plants were satisfactory 

with N levels of 50 and 100 ppm and P levels of 4.5 and 9 ppm in twice-weekly liquid 

feeding (Matthews 1993). 

Parvin (1986) reported on the application of tissue analysis to understanding the 

nutritional requirements of Leucospermum. Samples of recently matured leaves from 

the most recently matured vegetative flush of growth were collected from healthy green, 

51

field-grown plants. The analyses (Table 2.6) were used to define a baseline against which 

abnormal plants could be compared. Seasonal variation existed, but only calcium and 

magnesium showed large differences between the vegetative growing period of summer 

and the inflorescence development period of late fall, with higher values for the former than 

the latter. Sanford (1978) found little relationship between amounts of N, P, and K applied 

as fertilizer and foliar levels of the same nutrient. In his study, foliage N ranged from 

1.27 to 1.38%, P was in the range of 0.14 to 0.16%, and K ranged from 0.62 to 0.67% 

in recently expanded leaves. 

Using sand culture, Claassens (1986) determined that Leucospermum 

cordifolium responded better to ammonium than nitrate forms of N, although this species 

tolerated nitrate better than did the genus Protea. Analyses for the highest dry matter 

yield showed somewhat higher tissue concentrations for P, K, and Ca and lower N than did 

Parvin's fieldgrown plants (Table 2.6). He also analyzed the flower heads of 

unfertilized veld plants and his fertilized sand culture plants and found trends to be similar 

except for nitrogen. Claassens concluded that higher N levels contributed to higher yields 

as well as to a higher nutrient content, and that N in the ammonium form is the predominant 

element that needs to be managed in culture. Witkowski (1989, 1990) reported that L. 

parile stored N in leaves and twigs and used it during inflorescence production during 

the next year. Claassens's (1986) study was cited by Brits (1990c), with the additional 

information that certain ecotypes originating on calcareous soils tolerated higher 

concentrations of N03, NH4, P, alkalinity, and total salts than ecotypes originating from 

more acidic soils. Brits suggested that such characteristics might be a useful guide to 

selecting rootstocks. Malan (1996), on the other hand, offered the opinion that fertilization 

may be so dependant upon variety and site characteristics that recommendations 

would need tailoring to specific conditions. 

Table 2.6. Foliar and flower head tissue analyses of Leucospermum cordifolium. 

(Parvin 1986 and Claassens 1986). 

Content (% Dry Weight) 

Foliage Flower Head z 

Element Parvin y Claassens Veld Sand culture 

N 1.18 0.86 0.50 2.00 

P 0.09 0.12 0.08 0.15 

K 0.49 1.39 1.40 1.60 

Mg 0.22 0.20 0.60 0.60 

Ca 0.53 1.05 0.20 0.25 

S 0.14 

z Claassens 1986. 

y Content for microelements (ppm): Al (190), Cu (6), Fe (118), Mn (248) and Zn (30). 

6. Production Period. 

Although there are nearly 100 Leucospermum cultivars available, the exporters 

see a need only for a few lines that cover the entire marketing period. Since a cultivar 

typically blooms for only 4 to 6 weeks, approximately 6 to 8 cultivars flowering in 

succession would cover the late winter to late spring marketing period (Brits 1992b). 

These would include the basic color lines and early, mid-season, and late production 

periods. Parvin (1974) reported that 65-75% of the total crop of L. cordifolium ‘Hawaiian 

Sunburst’ was harvested during the December through February time period in Hawaii. 

During a three-year study, beginning with 6-year-old plants, the per-plant yields 

averaged 600 to 650 flowers. Approximately three years transpires under Hawaii 

52

conditions from initial seeding or rooting of cuttings before commercial levels of flower 

harvesting develop (Parvin 1974). Jacobs (1976) suggested that the flowering season could 

be extended by developing clonal selections from early- and late-flowering seedling 

populations (Fig. 2.4). His data showed that 50% of the crop could be harvested in 14 

to 29 days, but through suitable selections, the marketing season could be extended 

over four to five months. Leucospermum releases of the ARC Fynbos Unit extend the 

season from mid-August (late winter) to mid-November (mid-spring) (Table 2.7). 

Figures above horizontal bar indicate percentage of crop harvested. 

Figures below horizontal bar indicate number of days. 

Fig. 2.4 Distribution of flowering in a seedling population of Leucospermum 

cordifolium in South Africa. Source: Jacobs 1976. 

7. Growth Regulator Studies. 

Long, strong stems are desired by the cut flower growers, but some Leucospermum 

species and hybrids produce stems too short to be of commercial value. Napier et al. 

(1986a,b) investigated the influence of single and multiple sprays of GA at 1000 mg/L on a 

hybrid of L. conocarpodendron × L. cordifolium during the summer vegetative growth 

stage. They noted that GA applications were ineffective in causing elongation when 

shoots were reproductive, but internodes between basal bracts of the shoot were 

elongated. Multiple applications of GA caused a marked increase in stem length 

without affecting shoot diameter. The dry weight per unit length of shoot was 

decreased because of smaller leaves. In a concentration comparison, GA at 750 mg/L 

applied five times at three-week intervals provided optimal shoot elongation, while 

53

higher concentrations caused damage to the leaves and shoot tip, and shoot diameter was 

thinner. 

Table 2.7. Color and flowering periods in the western Cape (South Africa) for 17 

Leucospermum cultivars released by the Fynbos Unit of the Agricultural Research 

Council of South Africa (Brits 1992b). 

Color Early 

Flowering Period 

z 

Mid-season y Late x 

Yellow 'Yellow Bird' L. 'Goldie' L. 

cordifolium 

'Luteum' L. reflexum 

'High Gold' L. 

cordifolium × L. 

patersonii 

cuneiforme 

Red 'Sunrise' L. 'Flamespike' L. 

cordifolium x L. cordifolium 

patersonii 

'Fire Dance' L. 

'Vlam' L. 

cordifolium 

cordifolium 

Pink/Pastel/ 'Succession 1' 'Scarlet Ribbon' L. `Pink Star' L. 

Novelty lineare-type glabrum × L. tottum cordifolium 

'Helderfontein' L. 'Tango' L. glabrum × L. `Caroline' L. 

glabrum lineare 

cordifolium × L. 

tottum 

‘Starlight’ linearetype 

‘Succession 2’ lineare- ‘Ballerina’ lineare- 

z 

Middle August to end of September 

y 

Middle September to end of October 

x 

Late September to mid-November 

typetype 

In a similar field study on a L. conocarpodendron × L. cordifolium hybrid, 

Malan and Jacobs (1992) reported that a single GA3 spray at 500 mg/L, when shoots 

resulting from pruning were 10 to 17 cm long, markedly increased the number of 

shoots longer than 30 cm when compared to control plants. Pruning was done in late 

winter to leave a stub about 20 cm in length, and the GA application was made 10 to 12 

weeks later. Their study included multiple applications, but only up to 3, a month 

apart, and shoot length increased with multiple applications, as in Napier's study. 

Internode length was affected only slightly (no data presented), but node count was 

increased significantly. Their final recommendation of 500 mg GA3/L was based on the 

economics of GA application, higher concentrations being uneconomic in their opinion. 

Application of the cytokinin benzylaminopurine (BA) to developing 

inflorescences of ‘Red Sunset’ increased the number of florets in the inflorescence as well 

as dry weight, but also caused abnormal peduncle growth (Napier et al. 1986b). A single 

application made early in the development of the inflorescence increased floret number 

by 45%, while multiple applications added only slightly more, although dry weight 

of the inflorescence increased as the number of BA applications increased to four. Malan et 

al. (1994c) reported that apices of BA-treated shoots were larger than those of untreated 

shoots and more bract and flower initials were produced as a result, thus confirming the 

observations of Napier et al. (1986a). Spray applications of BA after inflorescence 

initiation stimulated the development of several inflorescence buds on the same branch, 

54

a process that ended in the abortion of the inflorescence buds (Wallerstein and Nissim 

1988). Dupee and Goodwin (1990) reported that application of gibberellin (GA4+7 or GA3) 

or paclobutrazol to initiated flower buds enhanced flowering by 3 to 9 days. Terminal bud 

removal delayed flowering, while terminal bud removal and treatment of the next bud with 

GA4+7 hastened the development of the secondary bud. Spray applications of GA to 

initiated inflorescences accelerated development, but also caused flower bud abortion 

(Wallerstein and Nissim 1988). Ethephon (960 mg/L) is also being used on mother plants 

to induce multiple branches on shoots to be harvested and used as cuttings for potted plant 

production (Brits et al. 1992). 

The use of auxins for rooting of cuttings is treated under propagation. 

Ethephon application (500 mg/L) to decapitated shoots reduced their 

responsiveness to inductive short days (Napier and Jacobs, 1989). Ethephon also 

enhanced the loss in responsiveness to short days when the plants were grown under 

shade. It is not clear how ethephon interacts with the lowered carbohydrate status of the 

shoot to reduce flower initiation. 

D. Plant Protection 

1. Diseases. 

Among the important diseases affecting Leucospermum are root and collar rots 

caused by Phytophthora cinnamomi Rands and P. nicotianae Breda de Haan, leaf spots 

and stem cankers caused by Dreschslera dematioideo (Bubak and Wrobl.) Subramanian 

and P. C. Jain, and D. biseptata (Saci and Roum) M. J. Richardson and E. M. Fraser, a stem 

and leaf scab caused by a Sphaceloma (= Elsinoe telomorph) sp., and a canker and 

dieback caused by Botryosphaeria dothidea (Moug:Fr) Ces and De Not. (Von Broembsen 

1985, 1989; Von Broembsen and Van der Merwe 1985; Knox-Davies et al. 1988; Kent 

1989; Nagata and Ferreira 1991, 1993). Botrytis cinerea Pers.:Fr also colonizes young 

shoot tips and buds of Leucospermum (Cho 1977). The aerial diseases are favored by 

conditions where dew or fog persist in the mornings and are transmitted by splashing 

water and cuts caused by pruning and flower harvest. The Dreschlera group and 

Sphaceloma (Elsinoe) require free water for conidial germination (Benic and Knox-Davis 

1983; Kent 1989). 

The first report of verticillium wilt on any protea species appeared in 1991 (Koike 

et a1. 1991), when affected plants of L. cordifolium collapsed and died. Symptom 

expression included terminal shoot wilting, fading of foliage to light green and 

eventual collapse and browning of the entire plant. Brown flecking and streaking 

were apparent in the stem xylem tissue. Verticillium dahliae Kleb was isolated and 

its pathogenicity confirmed by inoculation into and reisolation from cuttings of L. 

cordifolium cv. Firewheel. 

In the long term, breeding for disease resistance is a desirable alternative to 

fungicide use, but with the past emphasis on breeding for flower qualities, little 

progress has been made. Some progress has been reported in breeding for Phytophthora 

tolerance and Dreschlera resistance (Von Broembsen and Brits 1985, 1990), but all 

species evaluated lacked resistance. Good tolerance was shown for several hybrids and 

species selections and some tolerance appeared to be expressed within L. cordifolium 

(Von Broembsen and Brits 1990). Leonhardt et al. (1995) reported some resistance to 

Sphaceloma (Elsinoe scab disease) in L. conocarpodendron and L. reflexum. They have 

also found some interspecific hybrids with resistance to Sphaceloma, Botrytis, and 

Dreschlera. Matthews (1988) reported that L. patersonii showed some resistance to 

pincushion scab with a cultivar 'Goldie' completely resistant. 

Protective fungicides (e.g., mancozeb, iprodione, chlorothalonil) are 

recommended, as well as regular sanitation to remove diseased or dead plant parts. 

Control of canker and dieback was achieved by a single spray application of benomyl 

immediately after pruning. Since Leucospermum is extremely susceptible to 

55

Phytophthora (Von Broembsen and Brits 1985), control measures include avoiding 

poorly drained sites, planting disease-free nursery material, and fumigating the soil 

with methyl bromide prior to planting. Soil solarization has also been recommended 

(Knox-Davies 1988). Systemic fungicides have given inadequate control or are 

phytotoxic. 

Control measures for many foliar diseases include roguing, sanitation, disinfection 

of pruning shears, and application of fungicides. Over-reliance on broad-spectrum 

fungicides such as benomyl has fostered resistance among some pathogens (Cho 1977). 

Due to the ever-changing spectrum of chemical controls, it is impractical to attempt to list 

effective materials, but useful resources include Protea Diseases (Von Broembsen 1989), 

Protea Diseases and Their Control (Forsberg 1993), and the occasional publication of The 

Protea Disease Letter (Nagata and Ferreira 1991, 1993) by the University of Hawaii. 

An interesting biological control approach against Phytophthora cinnamomi 

utilized selected strains of Pseudomonas cepacia (Turnbull et al. 1989). Among the 

Proteaceae, Leucospermum was still susceptible to the root rot when inoculated with 

Pseudomonas cepacia, but plant mortality was slightly reduced. The promise of biological 

control, at least for Leucospermum, remains unfulfilled. 

2. Nematodes. 

Root-knot nematodes can severely limit growth and productivity of Leucospermum 

(Cho and Apt 1977). Heavily infected plants show stunting and chlorosis, followed by 

death of the plant. Treatments with phenamiphos and the fumigant 

dibromochloropropane (DBCP) increased shoot growth and flower production (Cho et 

al. 1976). The root-knot nematode [Meloidogyne incognita (Kofoid and White) 

Chitwood] decreases cut flower yields by at least 25% in infected fields compared to - 

fumigated fields with an optimal irrigation regime (Wu et al. 1978). Under drought 

conditions or with minimal irrigation however, yields were comparable. 

3. Insect Pests. 

Three general categories of insect pests that damage proteas are (1) flower visitors, 

which may or may not damage the flowers but which are quarantine problems because 

the flowers must be marketed insect-free; (2) leaf feeders, leaf miners, and sap suckers, 

which cause aesthetic damage to the foliage of exported cut flowers; and (3) borers, which 

use protea stems and flowers as their hosts (Coetzee 1987a, 1987b). Occasionally 

centipedes and snails are found in the flower heads. A "Witches Broom" stem 

proliferation condition in protea may be caused by a mite (Aceria proteae) (Coetzee 

1987a). Seed predation is a problem both in the wild and for propagators of proteas from 

seed (Coetzee and Giliomee 1987). Effective registered pesticides exist for some of the 

pests, but differ from country to country. 

4. Weeds. 

Nishimoto (1975) reported little or no injury from high rates of dichlobenil and 

oxadiazon (Ronstar) on trickle-irrigated Leucospermum planted 8 months prior to 

treatment. However, slight to severe injury was reported from simazine, ametryne, and 

diuron, especially at high rates. Weed control from all treatments was good. DeFrank and 

Rauch (1988) achieved acceptable weed control from pre-emergent sprays of 

oxadiazon and oxyflurofen 2% + oryzalin 1%, but noted that a black plastic woven ground 

cover suppressed all weed growth, which has since become an accepted weed control 

practice in Hawaii. For grass weed control, DeFrank (1990) recommended the postemergent 

herbicides: fluazifop-butyl (Fusilade), sethoxdim (Poast), DPX 6202 (Assure), 

and RE-36290 (Selectone). DeFrank and Rauch (1988) achieved satisfactory post-emergence 

grassy weed control with the manufacturer's recommended rate of fluazifop-P, but noted 

that a 4X rate could damage Leucospermum flower buds. 

56

E. Postharvest Studies 

1. Handling and Storage. 

Except in southern California, proteas tend to be grown in areas far distant from 

their markets. As most proteaceous flowers are heavy and/or bulky, air shipment is 

expensive, and shippers have investigated slower shipment methods, including 

seafreight. Pincushions are normally harvested with at least the first row of styles 

open, but this varies with the cultivar and destination. For packing into boxes, 

inflorescences with too many open styles are not desired because of tangling. On average, 

about 50% of the styles are open (Matthews and Matthews 1994). 

Research on postharvest handling practices has shown that the pincushion protea 

will tolerate cool, dry, long-term storage and still provide a useful vaselife. L. cordifolium 

flowers that were cooled and hydrated at 1°C in water, wrapped in newsprint and 

bagged in plastic film withstood periods of three and four weeks of 1°C storage, and after 

rehydration, possessed an average vaselife of 8 days, versus 9 days for untreated controls 

(Jones and Faragher 1990). Haasbroek et al. (1973) successfully stored L. cordifolium at 

1.7°C for 3 and 4 weeks without significant deterioration in vaselife. Downs and 

Reihana (1986) found significant varietal differences in vaselife following a period of 

simulated transport, with the New Zealand cultivar Harry Chittick at 35.5 days, a 

Hawaii hybrid of L. lineare × L. cordifolium at 29.7 days, and a South African hybrid 

(L. glabrum × L. conocarpodendron) Veldfire at 16.9 days. 

Parvin (1978) improved vaselife of Leucospermum cordifolium by 44 to 48% 

through the use of a 2 to 4% sucrose plus 200 to 600 ppm hydroxyquinoline citrate 

"preservative" solution. Silver nitrate at 1000 ppm was not beneficial for the cultivars of 

L. cordifolium but improved vaselife for the L. conocarpodendron × L. cuneiforme 

hybrid, ‘Hawaii Gold’ (Parvin and Leonhardt 1982). 

Since the mature, expanded pincushion flower occupies as much room in a 

shipping carton as a standard chrysanthemum, investigations were undertaken into the 

revival of wilted flowers with extruded styles, which could be packed more tightly. 

Flowers pulsed with a preservative prior to partial dehydration (20% loss of FW) and 

storage (24 h at 13°C) could be revived, although vaselife was not as long as with fresh 

cut flowers (Criley et al. 1978a, 1978b). Leucospermum flowers cut in bud (7 cm 

diameter) offered better promise, however, with full development and less loss of vaselife 

than flowers cut at a younger stage (Criley et al. 1978a; Parvin and Leonhardt 1982). 

2. Insect Eradication. 

A variety of approaches has been used to eradicate insects from the flower 

heads before shipping. Maughan (1986) reported that fumigation of various Protea spp. 

with methyl bromide, carbon dioxide, nitrogen, sulfur dioxide, dichlorvos, pyrethrum, 

and combinations killed varying amounts of insects, but often damaged the flowers or 

decreased vaselife. Treatments combining carbon dioxide with pyrethrum or diclorvos 

required exposures up to 30 h for 100% kill, but did not produce marked damage. 

Magnesium phosphide gas plus dichlorvos also has given excellent control (Wright 

and Coetzee 1992), as has a pressurized aerosol of dichlorvos (Coetzee 1987b; Wright 

1992). Vapor heat treatments of 10 min at 56°C or 66°C decreased vaselife of cut 

Banksia prionotes by 21% and 49%, respectively, while hot water dips of 30 min at 

46°C or 10 min at 56°C damaged the inflorescences and reduced vaselife by 25% and 

37%, respectively (Seaton and Joyce 1993). 

Gamma irradiation of protea flowers effectively killed earwigs, spiders, weevils, 

millipedes, and ants after 50 minutes of exposure (0.1 to 2.9 megaRads) without serious 

leaf blackening, but the experiments did not include Leucospermum (Wright and 

Coetzee 1992). At a dose required to kill insects (10 k Gy), flowers and leaves of 

Banksia were damaged (Seaton and Joyce 1992). In the only similar work mentioning 

Leucospermum, inflorescences with 50% of the styles reflexed were subjected to 30 

Krads of gamma irradiation (Haasbroek et al. 1973). Evaluation of the flowers and foliage 

57

after irradiation, 36 h storage at 15°C, and rehydration in a preservative solution showed 

little or no damage and a vaselife of 28 days versus 23 days for blooms with no 

irradiation treatment. Since corroborating data is lacking, it is not clear whether 

Leucospermum is more tolerant to gamma irradiation than other proteaceous flowers or 

whether the conditions of this experiment were unique. 

3. Grades and Standards. 

For many years, harvest of pincushions from natural stands in the veld resulted in 

mixed quality and lack of uniformity of the product (Littlejohn et al. 1995). This 

situation improved as pincushions moved to more distant cultivation areas and seedlings 

and selections were planted out. Little effort was made to manage the plants for longer, 

straighter stems. Initially, the wholesale and retail florists accepted mixed qualities, but 

the existence of standards for most floricultural crops stimulated a similar request for the 

proteaceous cut flowers as well. An early attempt to gain approval for grades and 

standards for cut pincushion flowers (Hawaii Dept. Agr. 1980; Table 2.8) failed to enlist 

grower support. A major deficiency of this proposal was acceptance of short stem 

flowers. The Flower Export Council of Australia (1992) circulated a draft grades and 

standards proposal (Table 2.9). 

Where they languish, grades and standards need to be implemented, if only to 

improve communication in the overseas flower markets that exporters have targeted. The 

IPA itself should develop a set of standards for stem length and straightness; flower shape 

and freedom from defects, insects, and diseases; and descriptions for single- and multipleheaded 

stems. Tables 2.8 and 2.9 present a platform from which to start. 

Table 2.8. Standards proposed for Leucospermum cordifolium by the Hawaii 

Department of Agriculture (1980). 

Standard 

Class (Grade) 

Extra fancy Fancy 

Stem length from 

cut end to base 

of flower head 

> 23 cm 15 to 23 cm 

Flower Full head, well-formed and 

symmetrical, well 

developed, more than 1/2 

styles reflexed, well 

colored, and typical of the 

species. 

Full head, well-formed and 

symmetrical, well 

developed, more than 1/2 

styles reflexed, well 

colored, and typical of the 

species. 

Clean, properly trimmed, free Clean, properly trimmed, 

from injury. 

free from injury. 

Angle of flower head not 

more than 90 0 to the stem. 

Angle of flower head not 

more than 90 0 to the stem. 

Foliage Leaves stripped from lower Leaves stripped from lower 

3/4 of stem. 

3/4 of stem. 

Slight defect or blemish Slight defect or blemish 

permitted. 

permitted. 

Stem straightness Curvature not to exceed 2.5 Curvature not to exceed 2.5 

Tolerances for 

defects and offsize 

cm from a straight line. 

Not more than 2% by count 

may fail to meet the 

requirements of the grade 

or the stem length. 

cm from a straight line. 

Not more than 2% by 

count may fail to meet 

the requirements of the 

grade or the stem length. 

58

Table 2.9. Flower Export Council of Australia proposed standards (1992) for cut 

Proteaceae (Leucospermum). 

Class (Grade) 

Standard Extra class Class 1 

Minimum length 60 cm 40 cm 

Flower Well formed. Reasonably well-formed. 

Sound, clean, uniform, of 

good color and size, no 

abnormal external 

moisture, fresh in 

appearance, insect- and 

disease-free. 

Proportion of reflexed styles 

< 5%. 

Flowers not hidden by 

leaves. 

Foliage 90% leaves intact on not less 

than 50% of stalk below 

flower head. 

Sound, clean, uniform, of good 

color and size, no abnormal 

external moisture, fresh in 

appearance, insect- and 

disease-free. 

Proportion of reflexed styles < 

5%. 

Flowers not hidden by leaves. 

90% of leaves intact on not less 

than 50% of stalk below 

flower head. 

Clonal Flowers of clonal origin. Flowers typical of the variety. 

Typical of variety and Typical of species. 

species. 

Single bloom Stems straight (no more than Straight stem with flower head 

10° bend). 

no more than 45° bend. 

Tolerance for 

defects and 

blemishes 

5% 10% 

F. Genetic Improvement 

One of the first Leucosperm um hybrids to be registered was a red hybrid named 

‘Mars’, selected in 1969 by the late F. C. Batchelor on his Protea Heights farm from a 

Leucospermum cordifolium population after five generations of mass selection (Brits 

1984a, 1985a). As of the fourth edition of the International Protea Register (International 

Registration Authority: Proteas 1997), 30 cultivar names have been registered and 

another 58 have been noted but not registered for selections and interspecific hybrids of 

Leucospermum. 

Breeding objectives for proteas have mostly focused on new flower colors, 

improved productivity, and a longer season of bloom, but characteristics such as 

improved postharvest life, disease resistance, and slender, longer, and straighter 

stems, reduced leaf pubescence, and smaller leaves have also received attention (Brits 

1992a, 1992b; Ito et al. 1990; Leonhardt et al. 1995). L. lineare has been used to contribute 

slender, light-weight stems with narrow, pubescence-free foliage, all qualities sought 

by flower exporters (Leonhardt et al. 1995). L. lineare contributes earliness to hybrids 

with L. cordifolium, while L. tottum contributes a later flower season (Jacobs 1976). 

Interspecific hybrids of L. lineare with L. cordifolium have been selected that markedly 

extend the normal flowering season in South Africa (Brits 1992b). Active breeding 

programs are being conducted at the Fynbos Research Station, Elsenburg, South Africa 

(Brits 1992a, 1992b; Littlejohn et al. 1995) and at the Maui Research Station of the 

University of Hawaii (Ito et al. 1978, 1979, 1990, 1991; Leonhardt et al. 1995), and in 

Israel (Shchori et al. 1995). 

59

Breeding and selection require 10 to 15 years, although some hybrids have been 

produced in less than 10 years (Ito et al. 1990). In Israel, evaluation of hybrids between L. 

patersoni and L. conocarpodendron yielded four high-yielding cultivars tolerant of high 

pH soils and a rootstock cultivar in only four years after planting out (Shchori et al. 

1995). Ackerman et al. (1995) selected plants tolerant to high pH, calcareous soils, 

from seedlings of L. patersoni. One selection, designated ‘Nemastrong’, was also 

tolerant to nematodes. A cross between L. patersonii and L. conocarpodendron, 

designated ‘Carmeli’, also demonstrated excellent resistance to high pH and calcium. 

Both selections root well from cuttings and have good grafting characteristics. 

60 

G. Leucospermum as a Pot Plant 

While a number of the Proteaceae may be grown as potted plants, the Leucospermums, 

with their relative ease of rooting and attractive floral display, have the greatest potential 

(Sacks and Resendiz 1996). Plants for sale need to be offered with several buds open. High 

light intensity is necessary for flowering (Jacobs and Minnaar 1980; Napier and Jacobs 

1989; Ackerman et al. 1995) as well as for rapid rooting of cuttings. Research on the 

photoperiod responsiveness of Leucospermum (Wallerstein 1989; Malan and Jacobs 

1990) indicates that daylength manipulation may have implications for potted flowering 

plant production as well. 

Leucospermum species suitable for potted plants are of two types: those 

having a single large inflorescence, such as L. cordifolium, L. lineare, and L. tottum; 

and those with small multiple inflorescences (conflorescences) such as L. oleifolium, 

L. muirii, and L. mundii (Ackerman et al. 1995; Brits et al. 1992; Brits 1995a). It is 

important to select material that will root rapidly and support flower initiation and 

development on a young root system (Ackerman and Brits 1991; Brits et al. 1992). 

1. Production. 

Some pinchusions do not respond well to a short production cycle and must be 

grown on a longer cycle of 18 to 24 months (Ackerman et al. 1995). These include the 

multiple-headed species and some single-headed types. Branched cuttings are 

produced on the mother plant, rooted in late autumn, and kept under production an 

extra year to flower in the second season. Sacks and Resendiz (1996) use a 20-month 

production program, rooting cuttings in the summer, transplanting to 10-cm pots, and 

pinching to induce branching the following spring and potting up to 16-cm pots. Salable 

pots with 5 to 6 buds per plant are produced a year later. 

The growing medium should be lightweight but capable of holding sufficient 

water and nutrient cations (Brits et al. 1992). A medium of 10 peat:40 pine bark:50 river 

sand supplied with a liquid feed at each irrigation (77 ppm N, 5 ppm P, 63 ppm K, 23 ppm 

Ca, 8 ppm Mg, 1.8 ppm Fe, and a microelement complex) proved satisfactory (Ackerman 

et al. 1995), while Ben-Jaacov et al. (1989) reported successful cultivation in media of 4 

coarse peat:4 fibrous peat:2 vermiculite No. 6 or 3 volcanic tuff (8 mm):1 peat in 10-cm 

pots. Brits (1990a) provided a rapid production method using cuttings that had set buds 

on the mother plant (Fig. 2.5). Following rooting, the inflorescences developed, producing 

a marketable potted plant within 6 to 8 months after harvesting of the original cuttings. 

As one single flowering stem, the plants were not marketable because of weak stems and 

lack of fullness, but several single-stem cuttings per pot is feasible (Brits et al. 1992). 

Branched, budded cuttings are useable, but cultivar selection for the capacity to continue 

inflorescence development is necessary to avoid bud abortion during or following rooting. 

Alternative protocols for rapid pot plant production are illustrated in Fig. 2.6. Brits et al. 

(1992) suggested that taking the cuttings in late summer (earlier than the semi-hardwood 

stage) would overcome the problem of abortion of the primary flower bud and allow rooting 

to occur before initiation of flower buds. They suggested heading back soft terminals to 

harder subterminal wood.

Fig. 2.5 Original concept of rapid production of flowering Leucospermum potted plants 

from semi-hardwood cuttings rooted while bearing a flower bud. Source: Brits 

et al. 1992. 

Fig. 2.6 Alternative rapid production systems for Leucospermum potted plants in the 

southern hemisphere using cuttings harvested in different physiological stages. 

Source: Brits et al. 1992. 

61

Yoshimoto (1982) successfully rooted cuttings with branches stimulated by 

removing 6 to 10 cm of tip during spring and summer, but he was not successful in 

forcing flowering in the next season. At that time, the application of high light and 

photoperiod requirements was unknown. A significant advance in production of potted 

Leucospermum ‘Ballerina’ was reported by Brits et al. (1992). Branched shoots (Fig. 2.7) 

produced by spraying 960 mg ethephon/L on strongly elongating primary shoots about 10 

cm long on the mother plant were rooted and manipulated as potted plants. The resulting 

shoots had a wider angle to the primary shoot compared to hand-pinched controls and 

produced a more desirable shape for marketing. Observations from other studies (Brits et 

al. 1986; Jacobs and Minnaar 1980; and Napier 1985) suggested that shoot diameter was 

important for good flower initiation, and that cultivars should be selected for their capacity 

to produce flowers on relatively thin stems (ca. 3.5 mm diam.). Flowers were initiated 

on stem diam. of 4 to 5 mm in cut flower types, but on stems too long for well-proportioned 

potted plants. Species producing multiple inflorescences, such as L. mundii and L. 

oleifolium, were also recommended. 

Fig. 2.7. A shoot of Leucospermum treated with ethephon to induce multiple laterals. 

Photo: Criley. 

The L. lineare × L. tottum hybrid ‘Ballerina’ has been shown to have a high 

propensity to develop flowers even after cutting back (Brits et al. 1992; Ackerman et al. 

1995) (Fig. 2.8). In one experiment in which primary shoots on mother stock plants were 

tip-pinched, BA was applied, and the resulting shoots shaped on the mother plant before 

taking the shoot as a cutting. Following treatment with 4000 ppm KIBA, non-induced, 

branched cuttings of two cultivars rooted well in 4 to 5 weeks. ‘Ballerina’ tolerated the 

manipulations better than did ‘Tango’ (a hybrid of L. glabrum × L. lineare) with 80% of 

the rooted plants flowering on several branches the next spring versus a very low proportion 

for ‘Tango’. 

Growth regulators are being used to induce branching (Brits et al. 1992) and 

improve compactness, increase leaf number, and increase shoot diameter, with a 

concomitant improvement in the capacity to initiate inflorescences (Ackerman and Brits 

1991; Ben-Jaacov et al. 1990; Brits 1995a). These uses may apply to cutting 

62

manipulations on the stock plant as well as to plants already growing in containers. 

Brits et al. (1992) proposed a scheme for the rapid production of potted Leucospermum 

using paclobutrazol and BA on the mother plants (Figure 2.9). Ethephon may cause 

some shoot length reduction and is additive with paclobutrazol (Brits 1995a). 

Fig. 2.8. Diagram of sequential manipulations performed on ‘Ballerina’ Leucospermum 

lineare × L. tottum shoots, followed by rooting in early spring and resulting in 

branched potted plants flowering in December in the southern hemisphere. 

Source: Brits et al. 1992. 

2. Postproduction. 

Budded Leucospermum plants abort their young flowering buds if moved into 

low indoor light conditions. Ackerman et al. (1995) recommend that the first row of styles 

be released on the inflorescence as the minimum developmental stage. Following 

storage in darkness for up to 8 days at 4°C and 90% RH, budded plants of ‘Ballerina’ 

continued to flower without damage or reduction in quality. Under similar conditions, L. 

oleifolium and L. mundii suffered some bud damage and leaf discoloration and 

flowered for 17 and 7 to 10 days, respectively (Ackerman et al. 1995). 

IV. CROP POTENTIAL AND RESEARCH NEEDS 

As developing nations seek sources of foreign currency to support development and 

improve conditions for rural peoples, the export of flower crops has been an important 

component. However, such nations do not support research into the new floral crops, and 

the sources of knowledge will be the very nations whose growers will lose market share to 

the new competition. Nonetheless, a 1997 listing of IPA members revealed only 13 

different nations and did not include any from Asia or Central/South America. The same 

impetus that moved rose, carnation, and chrystanthemum production to Colombia, 

Ecuador, Mexico, and Kenya will also drive Leucospermum production to suitable 

climatic regions in nations with low land and labor costs. Interest is being shown in areas 

as diverse as Taiwan, China, Korea, southern France, Corsica, Chile, and El Salvador. 

63

Development of new protea-producing regions will come from joint ventures with existing 

growers. 

Since the market for proteas of all types is not yet saturated, particularly in terms 

of year-round availability, there is still room for both domestic and foreign 

production to increase. The few researchers involved with production of cut flowers 

and potted proteaceae have much work ahead of them before crop production practices 

reach the levels of sophistication attained by roses or carnations, for example. The 

challenge for producers is to identify and prioritize where to put limited financial 

resources in support of long-term as well as short-term needs. 

Fig. 2.9. Diagrams of basic rapid production systems of Leucospermum in the southern 

hemisphere. Seasonal manipulations are done on the mother plant primary shoots 

and on rooted cuttings and include, progressively, 1: control; 2: branching 

treatment; 3: growth retardation with paclobutrazol (PBZ); 4: shaping of pot plant 

64

y.heading back laterals; 5: benzyladenine treatment to increase number of 

inflorescence buds in types bearing conflorescences. Source: Brits et al. 1992. 

At the Sixth Biennial Conference of the IPA, Parvin (1991b) observed that the first 

decades of protea production were producer-driven: the novelty value was high, the 

supply was low, and almost any protea brought to market could be sold. He ventured 

that as wholesalers, retailers, and the ultimate consumer begin to appreciate quality, the 

markets will be driven by consumer preferences. Education of the consumer, 

determining consumer preferences, and controlling production to grow what the consumer 

wants are the future for the industry. 

The research needs of Leucospermum, as separate from other Proteaceae, are not 

so distinct, and there is a great deal of overlap in such lists (Brits et al. 1992; Brits 

1995c; Malan 1995). The categories for needed research range from gaining a better 

understanding of the biology and physiology of the subject plant to learning about 

marketing opportunities and requirements. 

Gathering and learning more about the varied germplasm is a high priority, 

especially with South African flora threatened by wild gathering, land clearance for crops 

and animals, and other forces inflicting loss of habitat. In the Leucospermum collections 

at the Fynbos Unit of the South African Agricultural Research Council, some forms can 

no longer be found in the wild. The germplasm base is especially valuable for 

breeding and crop improvement (Littlejohn 1995). Plant breeders have much to learn 

about the genetic bases for productivity, disease resistance, flower color, ease of 

propagation, and possibilities for manipulating flowering time. 

Nutrition remains an area of concern because of off-color foliage disorders, 

interactions with soil pH and soil type, and inadequate standards for tissue analysis and 

their interpretation as a guide to fertilization. Malan (1996) notes that the interaction of 

substrates, growing techniques, and nutrition on proteoid root development is unknown. The 

suggestion that ammonium nitrogen is favored by Proteaceae should be followed up, as well 

as alternative forms of phosphorus for fertilization. Development of Leucospermum as 

potted plants also requires an understanding of the fertilizer regime. The interactions of 

major and minor elements with the flowering process are not known, and this could be 

important in the timing of fertilizer application on growth and flowering. 

Increasingly, attention is being turned toward practices that spread seasonal 

production over longer periods, improve quality, and permit better management of the 

plants. Other culture and management issues requiring research include: salinity 

tolerance, irrigation frequency and amount, pruning for optimal flower production and 

plant growth habit, and the interaction of nutrition with vegetative and reproductive phases 

of growth. The culture of Leucospermum under protected cultivation and soilless culture 

systems is receiving attention in areas where the climate is marginal for outdoor culture 

(Allemand et al. 1995; Montarone and Allemand 1995). 

While vegetative propagation is not the problem with Leucospermum that it is with 

other Proteaceae, research continues to find more efficient and less costly systems. 

Bringing tissue culture from a laboratory level to commercial production volumes also 

represents a challenge, if not to research, then to the ingenuity of commercial 

laboratories. The introduction of rootstocks, such as ‘Spider’, (Van der Merwe et al. 1991) 

and ‘Nemastrong’ and ‘Carmeli’ (Ackerman et al. 1997) that are tolerant to diseases, easy 

to root as well as suitable for the technique of cutting grafting, and compatible with other 

species and hybrids, may accelerate plantings of Leucospermum in previously 

inhospitable sites. Israeli research has proven the value of adaptability testing in the 

development of rootstocks suitable to local soil types. 

Pest control remains an on-going problem area, not only for new insects, but 

also because of diminishing availability of registered chemical controls. Insect presence 

in cut flowers limits their use and export and is the impetus for finding improved practices 

to prevent their presence, remove them, or kill them (Seaton and Woods 1991; Wright and 

Coetzee 1992). Ants, while not damaging pests on their own, are well known for 

"managing" colonies of other insects that they bring into the inflorescences, and effective 

65

control measures need to be developed. The practices of Integrated Pest Management (IPM) 

have not been elaborated for Leucospermum, although the principles developed for other 

crops will certainly apply (Wright 1995). 

Control of diseases and nematodes faces the same problem of diminished 

availability of registered chemicals. The stem and collar rots caused by 

Phytophthora spp. are particularly difficult because the most effective fungicide, 

metalaxyl, is not registered for field use in protea. At present, use of Phytophthoratolerant 

rootstocks offers the best approach, while the traditional breeding approach 

will require many years to implement and may still find no genes for resistance in 

the species. The technologies of genetic engineering may yield useful results once 

resistance genes are identified. 

The minor crop designation under which all protea fall is a deterrent to rapid 

advances in finding herbicides that can be used among proteas, but progress can be 

expected here, especially when registrations permit a broad designation for ornamental 

use. Specific weeds may still pose a problem, however. The use of groundcover or sodcrops 

that can be mowed and managed to reduce their competition with the shallowrooted 

proteas offers some promise, especially when other advantages may accrue, such 

as nematode-repelling properties, reservoirs for predaceous insects, and nutrition (through 

the use of nitrogen-fixing legumes). 

Postharvest research is needed to determine optimum storage conditions, vaselife 

following pre-conditioning and storage treatments, hybrids with good vaselife, 

packing and shipping conditions, management of diseases, and disinfestation of insects. 

The post-production characteristics of potted Leucospermum and the production 

practices that influence them are also in need of elaboration. 

Marketing research is high on the list of priorities of commercial growers in all parts 

of the world. The needs range from product selection to identification of consumer wants, 

from postharvest handling and storage to packaging, and from identifying seasonal 

sources to the markets requiring the products available at any given time. 

At the Seventh Biennial IPA Conference in Harare, Zimbabwe, Kobus Steenkamp, 

Farm Manager of Protea Heights near Stellenbosch, recounted the story of a farmer who 

had won a million Rand in a lottery. Asked what he would do with the money, he replied, 

"I will just carry on farming until the money is finished." Mr. Steenkamp added, "I think 

one can run a sound business with proteas, but not easily get rich." 


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75

Protea: A Floricultural Crop from 

the Cape Floristic Kingdom ∗ 



ISBN 0-471-38789-4 © 2001 John Wiley 

& Sons, Inc. 

by: J.H. Coetzee and G.M. Littlejohn 

∗ Research conducted by the authors was supported by The Agricultural Research 

Council, the South African Protea Producers and Exporters Association, the European 

Commission (INCO-DC contract number IC18-CT97-0174), and the International Protea 

Association. 

3 

77


Protea, the most widely known genus of the Proteaceae, is now an important floral 

crop. Other genera in this family that are widely used in floriculture are Leucospermum 

(Criley 1998), Banksia (Sedgley 1998), and Leucadendron. Mimetes, Serruria, Aulax, 

Telopea, Grevillea, Isopogon, and Paranomus are used to a lesser extent. The name 

Protea, given by Linnaeus in 1753, referring to the Greek mythical god, Proteus, who 

could change his shape at will, is truly an apt name due to the wide diversity of this 

genus. The genus Protea is only found in sub-Saharan Africa and currently 114 species 

are described (Rourke 1980), with 14 subspecies recognized (Rebelo 1995). The tropical 

Protea species are widely distributed across sub-Saharan Africa and comprise 35 species 

(Beard 1992). Three of these tropical species are found in the summer rainfall region of 

South Africa: P. caffra, P. gaguedi, and P. welwitschii. The 89 species of Protea found in 

Southern Africa may be sub-divided into 20 groups of closely related species, shown in 

Table 3.1 (Rebelo 1995). The Cape Floristic Kingdom, a small strip of land between the 

towns of Grahamstown in the east and Clanwilliam in the west (Fig. 3.1) is home to 69 

endemic species of Protea (Rourke 1980). It is from these species that the commercially 

utilized species derive, and include the stately P. cynaroides with a flower diameter of up 

to 25 cm and P. scolymocephala with a flower diameter of approximately 5 cm. The Cape 

Floral Kingdom, one of the world’s six plant kingdoms, is also known as the Flora 

Capensis or the fynbos biome. This plant kingdom, ranking alongside the Holarctic, 

Palaeotropic, Neotropic, Australasian, and Antarctic Kingdoms that cover vast areas of 

the globe, is unique. Plants in this region are adapted to hot dry summer conditions and 

primarily acidic, nutrient poor soils. It comprises only 0.04% of the earth’s surface, but 

due to its remarkable plant species diversity (>8500 species of flowering plants) and high 

level of endemism, has been classified as a distinct phytogeographic region (Bond and 

Goldblatt 1984). 

Table 3.1. Taxonomic groupings within the genus Protea (summarized from Rebelo 

1995). 

Group Common Names Species 

Rodent Sugarbush P. amplexicaulis (Salisb.) R.Br., P. humiflora Andrews, P. 

cordata Thunb., P. decurrens E. Phillips, P. subulifolia 

(Salisb. ex Knight) Rourke 

Grassland Sugarbush P. caffra Meisn., P. petiolaris (Hiern) Baker & Wright, P. 

simplex E. Phillips, P. parvula Beard , P. dracomontana 

Beard, P. nubigena Rourke 

Shaving Brush Sugarbush P. inopina Rourke, P. glabra Thunb., P. rupicola Mund ex 

Meisn., P. nitida Mill. 

Red Sugarbush P. enervis Wild 

Mountain Sugarbush P. angolensis Welw., P. rupestris R.E. Fr., P. madiansis 

Oliv., P. rubropilosa Beard, P. comptonii Beard, P. 

curvata N.E. Br., P. laetans L. E. Davidson 

Savanna Sugarbush P. welwitschii Engl., P. gaguedi J.F. Gmel. 

Moorland Sugarbush P. asymmetrica Beard, P. wentzelana Engl. 

King Sugarbush P. cynaroides (L.) L. 

Snow Sugarbush P. scolopendriifolia (Salisb. ex Knight) Rourke, P. 

scabriuscula E. Phillips, P. cryophila Bolus, P. pruinosa 

Rourke 

Spoonbract Sugarbush P. roupelliae Meisn., P. eximia (Salisb. ex Knight) Fourc., P. 

compacta R. Br., P. obtusifolia H. Beuk ex Meisn., P. 

susannae E. Phillips, P. burchellii Stapf, P. longifolia 

Andrews, P. pudens Rourke 

78

True Sugarbush P. repens (L.) L., P. aristata E. Phillips, P. lanceolata E. 

Mey. ex Meisn. 

Bearded Sugarbush P. laurifolia Thunb., P. neriifolia R. Br., P. 

lepidocarpodendron (L.) L., P. lorifolia (Salisb. ex Knight) 

Fourc., P. coronata Lam., P. speciosa (L.) L., P. stokoei E. 

Phillips, P. grandiceps Tratt., P. magnifica Link, P. 

holosericea (Salisb. ex Knight) Rourke 

Dwarf-tufted Sugarbush P. lorea R. Br., P. scorzonerifolia (Salisb. ex Knight) 

Rycroft, P. aspera E. Phillips, P. scabrapiscina R. Br., P. 

piscina Rourke, P. restionifolia (Salisb. ex Knight) 

Rycroft, P. denticulata Rourke 

White Sugarbush P. subvestita N.E. Br., P. lacticolor Salisb., P. punctata 

Meisn., P. mundii Klotzsch, P. aurea (Burm.f.) Rourke, P. 

venusta Compton 

Bishop Sugarbush P. caespitosa Andrews 

Eastern Ground 

P. tenax (Salisb.) R. Br., P. foliosa Rourke, P. vogtsiae 

Sugarbush 

Rourke, P. intonsa Rourke, P. montana E. Mey. ex Meisn. 

Western Ground P. acaulos (L.) Reichard, P. angustata R. Br., P. laevi R. Br., 

Sugarbush 

P. convexa E. Phillips, P. revoluta R. Br. 

Shale Sugarbush P. mucronifolia Salisb., P. odorata Thunb. 

Rose Sugarbush P. scolymocephala (L.) Reichard, P. acuminata Sims, P. 

canaliculata Andrews, P. nana (P.J. Bergius) Thunb., P. 

witzenbergiana E. Phillips, P. pityphylla E. Phillips 

Penduline Sugarbush P. recondita H. Beuk ex Meisn., P. effusa E. Mey. ex Meisn., 

P. sulphurea E. Phillips, P. namaquana Rourke, P. 

pendula R. Br. 

While the prominent use of Protea today is as fresh or dried flower, the plant has 

had many uses in the past. Early European settlers in South wagon wheels. The bark of P. 

nitida was used in the tanning of leather and the leaves as a source of black ink (Rourke 

1980). Protea also had their uses in traditional medicine (Van Wyk et al. 1997). The 

nectar of P. repens, which is produced in copious amounts, was used by early European 

settlers as a remedy for chest disorders after being boiled to a syrup. The bark of P. caffra 

is used to treat bleeding stomach ulcers and diarrhoea. 

79

Fig. 3.1. Map of Africa, depicting the Cape Floristic Kingdom and the distribution of 

tropical Protea throughout Africa. 

II. HISTORY 

80 

A. Taxonomy and Cultivation 

The early taxonomical and cultivation history of Protea has been reviewed by 

Rourke (1980). A Dutch trade group collected the first Protea in 1597 and in 1605 

Clusius described P. neriifolia. Paule Hermann of the Netherlands collected Protea on

Table Mountain in 1672, but the descriptions were published in 1737. Sir Hans Sloane of 

London described P. repens in 1693 and Plukenett did likewise for P. scolymocephala 

and P. cynaroides in 1700. 

European collectors of exotic plants were the first cultivators of Proteaceae, from 

achenes collected by Masson in 1774. P. repens was the first recorded Protea species to 

flower outside its natural habitat. In 1803, P. cynaroides flowered in the collection of the 

Earl of Coventry, Croome, Worcestershire. The largest collection of 35 species was 

grown by George Hubbert in 1805 in the suburbs of London and, by 1810, 23 species of 

Protea were already grown at Kew Gardens. The Dutch and French showed great 

enthusiasm for Protea cultivation during this period. The first commercial distributors of 

Protea achenes were the London firm, Lee and Kennedy. Among their clientele was 

Josephine, wife of Napoleon. The industrial revolution in Europe and the British Isles, in 

the early 1800s, led to wide-scale heating of greenhouses and concomitant high humidity, 

conditions under which Protea would not grow, leading to a loss of interest in their 

cultivation. It was only in 1981 that P. cynaroides flowered once again in Kew Gardens. 

In this rich floral kingdom, the South African wild flower industry had a humble 

origin. Street hawkers began selling flowers, picked in the surrounding mountains, on the 

streets of Cape Town, a tradition still in existence (Coetzee and Littlejohn 1995). In the 

19th century, European church groups established settlements on their mission stations in 

the rural areas of the Cape, for people originating from the Khoi-San tribes, as well as 

slaves imported from the East, and European settlers. These inhabitants of the mission 

stations, at Elim and Genadendal, were the first exporters of dried indigenous flowers to 

Europe in 1886 (Krüger and Schaberg 1984). 

However, no interest was shown in the cultivation of Protea in the 19th century. 

In 1910, A. C. Buller cultivated P. cynaroides commercially for the first time on his farm 

near Stellenbosch. In 1913 the National Botanical Garden of South Africa at Kirstenbosch 

was established and proteas were among the first plants cultivated. The first seed trader 

selling proteaceous achenes was Kate Stanford, who issued a catalogue in 1933 (Rourke 

1980). Ruth Middelmann greatly promoted sales of proteaceous achenes, exporting 

achenes to countries such as New Zealand, the United States of America (California), and 

Australia (Lighton 1960). The Kirstenbosch botanical garden also introduced a system for 

the selling of achenes of plants from the Flora Capensis soon after its establishment. 

Frank Batchelor established the first commercial plantation on his farm in Devon 

Valley near Stellenbosch, the farm later to be known as Protea Heights, where he 

harvested the first flowers in 1948. In 1953 P. cynaroides was part of a floral basket sent 

as a gift from the people of the Cape to Queen Elizabeth on the eve of her coronation 

(Lighton 1960). This is the first documentation of fresh Protea being exported. Buller and 

Batchelor can be viewed as the fathers of the fresh, cut flower protea industry in South 

Africa. The commercialization of the dried flower industry began in the mid 1950s, with 

the Middelmann family exporting large quantities of dried flowers by ship to Europe. 

Today there are over 400 flower harvesters collecting plant material from the wild and 

delivering it to large dried flower businesses for drying and processing for export. In the 

South African dried flower industry, six Protea species are used (Table 3.2), from which 

a large number of products are created (Coetzee and Middelmann 1997). Twenty different 

products that originate from P. repens are sold (Wessels et al. 1997), with more than 20 

million inflorescences of P. repens harvested in the natural habitat annually to supply the 

market. The proteaceous material used in the dried flower industry is primarily harvested 

from the natural habitat and can have negative effects on the ecology of the fynbos, the 

re-establishment of the species after fire, and the genetic variability within a population 

(Coetzee and Littlejohn 1995). 

81

Table 3.2. Important Protea species used in the dried flower trade. 

Species Trade Name 

P. repens Repens flower, rosette 

P. compacta Compacta flower, rosette 

P. magnifica Barbigera flower 

P. susannae Susannae rosette 

P. neriifolia Neriifolia bud 

P. obtusifolia Obtusifolia flower 

The fresh cut flower industry utilizes 12 Protea species and a number of 

interspecific hybrids, listed in Table 3.3 (Coetzee and Middelmann 1997). Approximately 

350 growers cultivate Proteaceae commercially. Although some species of Protea are still 

harvested in the natural habitat and sold as fresh cut flowers, a recent survey indicated 

that more than 80% of the cut flower Protea are from cultivation (Wessels et al. 1997). In 

1997 the Proteaceae hectarage under intensive cultivation in South Africa was in excess 

of 400 ha, of which 50% were Protea (Middelmann and Archer 1999). A further 1,000 ha 

of broadcast sown plantations were recorded. During 1998, 3,666 tons of fresh cut 

flowers were exported from South Africa, of which 30% was represented by genus 

Protea. The top-selling products exported by South Africa are P. magnifica, P. repens, 

and P. eximia, representing 58% of exports of flowering stems. Large quantities of 

bouquets, many containing P. eximia or P. compacta, are also exported from South 

Africa. Export and local sale of Protea is throughout the year, with a peak in export 

quantities during October. 

Table 3.3. Important Protea species used in the fresh cut flower trade (Middelmann and 

Coetzee, 1997), with their natural flowering times in the Southern Hemisphere 

(Rebelo 1995). 

Flowering time 

Protea Species Trade name J F M A M J J A S O N D 

P. compacta 

P. cynaroides King 

* * * * * * 

z P. eximia Duchess 

* * * * * * * * * * * * 

z * * * * * * 

P. grandiceps 

P. lacticolor 

P. magnifica Barbigera 

* 

* * * * * 

* * * * 

z or 

82 

Queen y 

* * * * * * * 

P. mundii * * * * * * * * * 

P. nana * * * * 

P. neriifolia Mink y * * * * * * * * * * 

P. pityphylla * * * * * 

P. repens Sugarbush y * * * * * * * * * * * * 

P. scolymocephala Scoly z * * * * 

z South Africa 

y USA 

B. Research 

The domestication of Protea in South Africa began in 1913, with the inauguration 

of the National Botanical Garden at Kirstenbosch. The establishment of a collection of

Proteaceae led to the publication of an article on cultivation, titled “The cultivation of 

proteas and their allies” (Matthews 1921). It was only in the late 1950s that a scientific 

manual was published on protea cultivation: Proteas: Know Them and Grow Them 

(Vogts 1959). Due to the growing interest in South Africa in proteas as a floricultural 

crop, the South African Department of Agriculture initiated a research program on proteas 

in the 1960s, under the leadership of Dr. Marie Vogts. The first research phase dealt with 

the identification, collection, and establishment in cultivation of the protea species in 

South Africa with floricultural potential. The collection of economically important 

species was established at Oudebosch near Betty’s Bay. Ten years of research resulted in 

the identification of horticultural variants within species. The characteristics of these 

variants were stable when propagated by achenes (Vogts 1971). In 1973, a breeding and 

selection program was initiated at Tygerhoek, near Riviersonderend, about 150 km from 

Cape Town. The collection of proteas was moved from Oudebosch to the new site. The 

first Protea cultivar resulting from this program was Guerna (Plate 1), a P. repens 

selection (Brits 1985). During the period 1988 to 1992 the germplasm collection of 

Proteaceae, or what is known as the field genebank (Littlejohn and de Kock 1997) was 

moved from Tygerhoek to a new site, Elsenburg, an experimental farm near Stellenbosch. 

In April 1992, the genebank collection was transferred to the Agricultural Research 

Council (ARC), a non-profit, non-governmental organization. The ARC is responsible for 

the maintenance of the field genebank and to research the commercialization of Southern 

African Proteaceae. 

Research in other countries where Protea is cultivated has been undertaken by 

various research organizations, with individuals within the organizations playing critical 

roles. In Hawaii, research on propagation, cultivation, selection, and diseases has been 

undertaken since the 1960s by the University of Hawaii. In California, the University of 

California has played an instrumental role in importing new plant material and in research 

on leaf blackening. Proteaceae research in Australia is conducted by a number of different 

organizations in Western Australia and Queensland, while in New Zealand the 

Horticulture Research Centre in Levin conducted Proteaceae research (Matthews and 

Carter 1983). In France, research on cultivation in soilless medium under glass at the 

Sophia Antipolis INRA station is underway, and in Tenerife, Spain, the University of La 

Laguna is active in Proteaceae research. The Volcani Institute in Israel has done excellent 

research on cultivation of Proteaceae in calcareous soils. However, worldwide research on 

Proteaceae as a horticultural crop is decreasing, although many problems for cultivators 

of cut flowers still exist. In the 1980s an active International Protea Working Group was 

inaugurated (Lamont 1984) but, by the late 1990s, the membership had dwindled to five 

researchers. 

C. World Industry 

The Proteaceae of Southern Africa are also cultivated in many other countries, 

such as Australia, Chile, El Salvador, France, Israel, New Zealand, Spain (Canary 

Islands), Portugal, the United States of America (California, Hawaii), and Zimbabwe 

(Leonhardt and Criley 1999). Cultivation in many countries developed simultaneously 

with the industry in South Africa. 

In Australia, the Botanical Garden in Adelaide began cultivating Cape flora in 

1871 (Lighton 1960). The cut flower industry in Australia gained impetus when 

immigrants from South Africa, such as the Wood family, sold their farm in South Africa 

in 1984 and emigrated to Western Australia with large quantities of seed. Today, South 

African Proteaceae are cultivated in South Australia, Victoria, New South Wales, 

Queensland, and Western Australia, but no data exists on the extent of cultivation of the 

genus Protea. Large commercial plantations are especially found in the 

Busselton/Margaret River area of Western Australia. The largest nursery producing potted 

plants of various Proteaceae species is situated in Monbulk, Victoria, and is owned and 

run by the Matthews family. In New Zealand, origins are unclear, but it is widely believed 

83

that South African Proteaceae were brought there by soldiers returning from the Anglo- 

Boer War during the period 1899 to 1906 (Matthews and Carter 1983). In 1922, Duncan 

and Davies Nursery offered P. repens in their catalogue and Stevens Brothers began 

selling proteaceous cut flowers in 1945. Achenes imported from South Africa were used 

to hybridize the well-known Leucadendron cultivar, Safari Sunset. A Protea cultivar that 

originated from New Zealand is the P. repens hybrid, Clark’s Red. Proteaceae cut flowers 

are an important New Zealand export commodity, and are sold primarily to Japan and the 

Far East. There are no statistics on the extent of Protea plantations (Soar 1998). 

The industry in Hawaii developed from a research project on new cut flower crops 

at the University of Hawaii. While a visiting Professor in Hawaii, Sam McFadden, 

University of Florida, imported a wide variety of propagative material in 1964. Included 

were proteaceous achenes. In 1968, Phillip Parvin joined the Faculty as Research 

Horticulturist at the Maui Agricultural Research Center, and spent the next 25 years 

assisting in the development of the protea cut flower industry in Hawaii. Today, 

approximately 60 ha of Proteaceae are cultivated in Hawaii (Wilson 1998). 

The cultivation of South African Proteaceae in California was promoted by 

Howard Asper of Escondido, who imported many species during the 1960s. Today, 

approximately 450 ha are under woody Southern Hemisphere plants for cut flower 

production, of which approximately 20% is the genus Protea (Perry 1998). 

Zimbabwe is a recent entrant to the international trade in Proteaceae. The primary 

initiators of cultivation on a commercial scale were the Miekle family in the late 1970s. 

The first Protea cut flower exports were made in 1981. The Australian cultivar Pink Ice 

was cultivated on a large scale in Zimbabwe, but recent problems with disease and insects 

have drastically reduced the hectarage. Other Protea cultivars and species are being used 

and approximately 78 ha are under plantations, with 140 ha of other Proteaceae 

(Middelmann and Archer 1999). 

The area under cultivation of Proteaceae in South America is approximately 8 ha, 

with 0.5 ha in Chile (Lobos 1998) and 7.5 ha in El Salvador (Veltman 1998). Spain and 

Portugal have approximately 30 ha of cultivated Proteaceae, located mainly on the islands 

of Madeira (Fernandes and Blandy 1998) and Tenerife (J. A. Rodríguez-Pérez, pers. 

comm.). 

III. REPRODUCTIVE BIOLOGY 

The genus Protea range in size from small prostrate shrubs, some with 

underground stems, to large trees. All are evergreen, woody perennials with 

sclerophyllous leaves suited to withstand periods of hot, dry weather. Regeneration can 

take place through sprouting from the lignotuber in some species or by release of achenes, 

from infructescences maintained on the plant. The foliage varies from fine needle-like 

leaves in P. aristata to the petiolate oval or obovate leaves of P. cynaroides. The 

commercially valuable product in Protea is the terminal inflorescence. It is the size and 

color of the involucral bracts of the inflorescence, which range from greenish white 

through all shades of orange, pink, red to brownish-red that give the Protea their aesthetic 

appeal. The genus Protea is distinguished from all other African genera of the Proteaceae 

by its flowers. The perianth is bipartite, bilaterally symmetrical with the three adaxial 

perianth segments fused from the base of the tube to the tips of the limbs, forming a 

distinct sheath, while the abaxial perianth segment separates completely from the adaxial 

perianth sheath, falling free as each individual flower opens (Rourke 1980). Each flower 

is composed of four perianth segments and the individual flowers are aggregated together 

on the inflorescence, surrounded by a prominent involucre of colored and often tufted 

bracts. The involucral bracts provide the main floral display. The individual flowers 

develop spirally from the outer edge of the involucral receptacle. Three anthers are 

attached to the three fused perianth segments; the fourth anther is attached to the free 

perianth segment. The central pistil consists of an ovary containing a single ovule, a long 

84

style and a small stigmatic region at the tip of the style enclosing the stigmatic groove. 

The distal portion of the style is specialized to form the pollen presenter, the external 

morphology of which varies between species (Rourke 1980). The pistil of P. repens can 

be roughly divided into four major regions: the stigma, a vertebra-shaped upper style, a 

heart-shaped lower style, and the ovary (Van der Walt and Littlejohn 1996a). The upper 

pistil is modified to form the pollen presenter, an elongated, ridged structure where pollen 

is deposited prior to anthesis and a longitudinal obliquely placed terminal groove on the 

upper adaxial side of the stigma, the stigmatic groove. A layer of interlocking epidermal 

cells fringes the margin of the stigmatic groove. A stylar canal appears to run the length 

of the style, surrounded by densely packed transmitting tissue. The stylar canal joins up 

with the cavity formed between the ovule and the inner ovary wall. The ovary is partially 

embedded in the woody involucral receptacle of the inflorescence and contains one 

acutely obovate-shaped ovule. The observed pistil structure of P. repens is very similar to 

P. cynaroides (Vogts 1971), Macadamia (Sedgley et al. 1985), and Banksia (Clifford and 

Sedgley 1993). In all cases the style is woody, containing many sclerenchyma cells, but in 

Macadamia and Banksia the stylar canal does not extend along the entire length of the 

style. 

Trichomes are found on the outer surface of the ovary. After flowering, the 

fertilized ovules develop into obconic achenes, densely pubescent with long straight hairs, 

brown, rust-colored, black, or white (Rourke 1980). The viable achenes tend to be found 

in distinct groups, or clusters on the receptacle, which may be a mechanism to reduce 

insect predation (Mustart et al. 1995). It appears that the plant actively controls the 

clustering, but the mechanism of control is unknown. The achenes formed may be stored 

in infructescences, the woody flower receptacle enclosed by woody involucral bracts, on 

the plant (Bond 1984, 1985), with release being triggered when water supply to the 

infructescence stops, such as during a fire, at plant death, or when insects consume the 

infructescence stem. Protea adapted to arid conditions, such as P. glabra and P. nitida, 

release their achenes four to seven months after flowering. The function of the trichomes 

on the achenes is fourfold: (1) expansion of drying achenes assists in forcing the achenes 

from the drying infructescence, (2) on an airborne achene they assist with buoyancy in 

high winds, (3) they assist in anchoring the achene to the ground, and (4) they orientate 

the achene on the soil surface to ensure optimum water uptake for germination (Rebelo 

1995). 

The flowers of Protea are protandrous, with the anthers dehiscing prior to the 

flower opening (Van der Walt and Littlejohn 1996b; Vogts 1971). The anthers deposit 

their pollen on the pollen presenter. During anthesis foraging fauna collects the pollen. 

Three types of fauna assist in pollination of Protea: birds (predominantly Promerops 

cafer, the Cape Sugarbird); small mammals such as mice, rats, and voles; and many types 

of insects (Collins and Rebelo 1992). The shape of the style in mammal pollinated Protea 

is curved (Plate 2), while bird and insect pollinated species have straighter styles. It is 

generally accepted that the Protea with large conspicuous inflorescences are bird 

pollinated, but species differ in dependency on birds as pollinators. Inflorescences of P. 

nitida, P. cynaroides, and P. repens bagged to exclude bird pollinators, but not insects, set 

achenes at the same rate as unbagged inflorescences (Coetzee and Giliomee 1985; Wright 

et al. 1991). In P. neriifolia, P. magnifica, and P. laurifolia the bagged inflorescences set 

significantly fewer achenes. 

At anthesis the stigmatic groove has not yet become receptive to pollen. In a study 

on P. repens and P. eximia, the stigmatic groove was open at its widest between three and 

six days after anthesis (Van der Walt and Littlejohn 1996b). The number of pollen tubes 

per style and the achene set recorded from controlled pollination indicated that peak 

receptivity of the stigma was between two and six days after anthesis. Stigmatic 

secretions in P. eximia increased as the stigmatic groove opened. 

The genus Protea has an inherently low achene set, between 1% and 30% under 

natural pollination conditions (Rebelo and Rourke 1986; Esler et al. 1989). Reasons cited 

for low achene set range from direct plant control of achene set numbers, pollinator 

85

limitation, insect and mammal predation, and poor nutrition. The percentage of florets 

with pollen tubes, the percentage of ovules penetrated by a pollen tube, and the achene set 

in P. repens and P. eximia are highly correlated, indicating that entry of a viable pollen 

tube into the stylar canal results in a viable achene. In P. repens the achene set from 

controlled self-pollination, open pollination, and pollination between different clones of 

P. repens resulted in the same high achene set percentages of between 40% and 74% 

(Van der Walt 1995), while the achene set of P. eximia did not exceed 10%. This is 

contrary to the generally accepted view that all Protea are obligatory cross-pollinators 

(Horn 1962) and supports the observation that achenes resulting from insect pollination 

are likely to be from self pollen (Wright 1994a). Pollination does not occur without a 

pollen vector, such as an insect or bird (Brits 1983). 

IV. CROP IMPROVEMENT 

86 

A. Genetic Variability 

The growth habit differences between species range from the Eastern and Western 

ground sugarbushes that have underground stems, to upright bushes typified by P. eximia, 

and to trees, such as P. nitida (Rebelo 1995). Some species have a lignotuber (a swelling 

of the stem at or just below ground level, covered in dormant buds that can regenerate 

after a fire), such as P. cynaroides and P. welwitschii, but most species do not. Protea are 

described as evergreen, but species differences occur, with some species having leaves 

that live for one year, e.g., P. nitida, and others with leaves remaining on the bush for up 

to 6 years, e.g., P. neriifolia. Leaf shape varies from the narrow, elongated leaves of P. 

longifolia to the ovate leaves of P. cynaroides that have a prominent leaf stalk. 

Interspecific hybrids exhibit characteristics intermediary to the parental species, allowing 

for ease of identification of the parents of interspecific hybrids (Vogts 1989). The color of 

the involucral bracts varies from brown, through shades of deep crimson, red and pink, to 

white or pale green, both within and between species. Further variation in flower 

appearance occurs due to differences in the color of the trichome tufts, or beard, at the 

ends of the inner and outer involucral bracts, especially in P. magnifica. 

Plant species with a predominantly outcrossing breeding system generally show 

high levels of phenotypic variability. The amount of phenotypic variability within species 

differs widely between species of Protea. In species with a wide habitat range, such as P. 

cynaroides, P. neriifolia, and P. magnifica, distinct horticultural forms (Plate 3) can be 

recognized (Vogts 1989). Studies indicated that the variation observed between seedling 

populations of P. cynaroides sampled from different localities was consistent when the 

plants were cultivated at a single locality, and therefore had a genetic basis (Vogts 1971). 

This was useful in selecting achene propagated populations that could flower at different 

times of the year and thus supply marketable flowers for 12 months of the year. 

In species with smaller habitat ranges, such as P. compacta, few observable 

differences are recognized between populations (Vogts 1989). Currently studies using 

RAPD-PCR analysis are being done by the Agricultural Research Council in South Africa 

to compare the extent of variation between species with a wide habitat range and those 

with a small habitat range. This information will assist in determining the extent to which 

populations must be sampled from, to try to maximize the variation within species kept in 

genebanks, botanical gardens, and in cultivation. 

There is a high level of genetic variation present in P. neriifolia based on analysis 

of segregation after self-pollination (G. M. Littlejohn, unpubl.). Measurements of various 

traits on mature seedling plants obtained by self-pollination of a single selected clone of 

P. neriifolia showed significant variation between seedlings. The type of traits measured 

included growth habit, plant height, flower color, leaf length and width, inflorescence 

length and width, inflorescence mass, style length, and the concealment of the 

inflorescence by the leaves. Genetic improvement is closely linked to the process of

Plate 1 Protea repens cv. Guerna, the 

first Protea cultivar released in 1978 from 

the South African Proteaceae breeding 

project. 

Plate 2 Protea holosericea, a mammalpollinated, 

endangered species found in 

two isolated population in the Worcester 

district within the Cape Floristic 

Kingdom. 

Plate 3 The large-leaf, summer flowering horticultural variant of Protea cynaroides in its 

natural habitat.

Plate 4 Protea cv. Sheila, a putative 

hybrid between P. magnifica and P. 

burchellii, is an example of an 

interspecific hybrid produced by natural 

pollen vectors and selected for its unique 

involucral bract color, flower head shape, 

and the plant vigor. 

Plate 5 Protea cynaroides cv. Madiba, 

the result of controlled hybridization, was 

selected for its late spring flowering time, 

red involucral bract color, small leaves, 

thin stems, and strong plant vigor. 

Plate 6 The different flowering stages of a Protea repens hybrid, moving from left to 

right, the hard bud, soft bud, anthesis of first florest and progression of anthesis. The 

correct cut flower harvesting stage is from soft bud to anthesis of the first florets.

domestication of an essentially wild plant, such as the Protea (Brits et al. 1983). 

Domestication generally follows three phases: (1) the harvesting of wild flowers; (2) the 

selection of superior populations or clones; and finally, (3) the development of new 

variations by hybridization, aimed at improving traits of importance in cultivation (Brits 

1984). In a woody, perennial plant the breeding process is lengthy. The duration from 

collected wild plant material to acceptance of a cultivar developed by controlled 

hybridization can take up to 40 years (Fig. 3.2). This time span allows only for evaluation 

at one site, and no regional evaluation. Regional evaluation would increase the time span 

by four to six years (Wessels et al. 1997). 

Fig. 3.2. Sequence of events and time lapse in the development of a Protea cultivar, from 

selection of wild harvested material through controlled hybridization and the 

selection of a superior hybrid. 

87

88 

B. Selection 

The first stage in selection is the selection of species suitable for cultivation. Vogts 

(1989) provided Protea enthusiasts with a book on the Proteaceae and information on 

how to cultivate them. Of the species described in the book, 150 were identified as 

suitable for cultivation, with 86 having very good market potential (Brits et al. 1983). 

Characteristics sought for in suitable species included: attractive and arresting 

appearance, color, shape and size of flower head, foliage attractive but not dominating; 

flower head neither hidden nor pendulous; erect growth providing long, straight flower 

stems; good cultivation potential and ease of achene propagation; stability of characters; 

desired flowering time; post harvest quality; no obnoxious odor. 

Selection within a species can take two forms: selection for an improved 

population or selection of a unique individual from a population that is propagated 

clonally. Both of these methods have been used in Protea. The identification of 

horticultural variants within certain Protea species identified populations suitable for use 

in initiating mass selection for improving populations (Vogts 1989). 

Brits (1985) documented the selection of an achene propagated cultivar of P. 

repens, Guerna, which comprised 18 similar clones. Achene propagation or clonal 

propagation could be used. The success of selection of unique individual plants from 

within a population is dependent on the level of genetic variation present in the 

population from which one is selecting (Vogts 1989). Selection criteria for single plant 

selections are determined by the flower traits together with the producer requirements. 

These are summarized in Table 3.4. Single plant selections that have become successful 

cultivars include P. eximia cv. Fiery Duchess, P. magnifica cv. Atlantic Queen, and P. 

cynaroides cv. Red Rex (see Table 3.5). 

Table 3.4. The characteristics desirable in a single plant selection for use as a cut flower 

cultivar. 

Production characteristics Flower characteristics 

High yield 

Growth vigor 

Flower head color 

Flower head shape 

Longevity Attractive foliage that does not conceal flower head 

Ease of rooting Terminal flower with no secondary growth (bypass) 

Good regeneration after Straight stems 

pruning 

Tolerance to different soil Stems longer than 40 cm 

types 

Tolerance to cold Ease of packing 

Tolerance to heat Resistance to leaf blackening 

Insect resistance Vase life of 10 days minimum 

Ability to shift flowering time Involucral bracts that retain their turgidity and color 

and do not brown under hot, dry conditions 

Disease resistance Ease of removal of leaves on lower flower stem 

Table 3.5. Some cultivars in Protea, selected predominantly from chance hybrids or as 

single plant species selections, and recorded in the International Protea Register (Sadie 

1998). 

Putative parentage Cultivar names z 

P. burchelli/P. longifolia Nomad (SA) 

P. compacta/P. burchellii Brenda (SA)

P. compacta/P. eximia Pink Duke (SA) 

P. compacta/P. magnifica Andrea (SA), Lady Di (SA), Margot (SA), Pink 

Velvet (SA) 

P. compacta/P. neriifolia Carnivalz (SA) 

P. compacta/P. obtusifolia Red Baron (SA) 

P. compacta/P. susannae Pink Ice (Aus) 

P. cynaroides Artic Ice (NZ), Attaturk (Zim), Clarez (SA), Ivory 

King (Zim), Florindinaz (SA), Madibaz (SA), Red 

Rexz (SA) 

P. cynaroides/P. grandiceps Cottontop (SA), King Grand (SA) 

P. cynaroides/P. compacta Valentine (SA) 

P. eximia Duchess of Perth (Aus), Fiery Duchess (SA) 

P. eximia/P. susannae Baron (Aus), Cardinal (SA), Sylvia (SA) 

P. glabra/P. laurifolia Helzaan (SA) 

P. lacticolor/P. mundii Ivy (SA) 

P. laurifolia/P. sulphurea Pretty Annez (SA) 

P. magnifica Atlantic Queen (SA), Chelsea (SA) 

P. magnifica/P. burchellii Sheilaz (SA), Kurrajong Rose (Aus) 

P. magnifica/P. laurifolia Princess (SA) 

P. magnifica/P. longifolia Pinitaz (SA), Possum Magic (Aus) 

P. magnifica/P. neriifolia Pacific Queen (NZ), Venetia (SA) 

P. magnifica/P. obtusifolia Candidaz (SA), Ruthz (SA) 

P. magnifica/P. susannae Susara (SA) 

P. mundii/P. subvestita Empathy (Zim) 

P. neriifolia Frosted Fire (Aus), Pretty Belindaz (SA) 

P. neriifolia/P. repens Nataliaz (SA) 

P. neriifolia/P. longifolia Barber’s Hybrid (NZ), Anneke (SA) 

P. obtusifolia Davidz (Is), Jossefz (Is), Michalz (Is), Shlomoz (Is) 

P. pityphylla/P. effusa Ansiz (SA), Lizlz (SA), Petrouxz (SA), Riaz (SA) 

P. pudens/P. longifolia Pixiez (Aus) 

P. repens Embers (SA), Guerna (SA), Rubens (SA), Sneyd 

(SA), Sugar Daddy (SA) 

P. repens/P. longifolia Liebencherryz (SA) 

P. repens/P. mundii Sweet Suzyz (SA) 

P. repens/P. aristata Venusz (SA) 

P. repens/P. aurea Clark’s Red (NZ) 

P. repens/P. pudens Kurrajong Petite (Aus) 

Key: z Protected by plant breeder’s rights, or under application; Aus = Australia, Is = Israel, NZ = New 

Zealand, SA = South Africa, Zim = Zimbabwe 

Early in the development of the fledgling protea industry in South Africa, it was 

observed that chance occurring interspecific hybrids produced new, unique flower forms, 

the plants often exhibiting greater vigor than either parental species (Vogts 1989). This 

led to the active search for interspecific hybrids by growers and the selection of many of 

these as cultivars, all clonally propagated by means of cuttings (see Table 3.5). This was 

also the impetus behind the initiation of a controlled breeding program, based primarily 

on the development of interspecific hybrids. 

C. Hybridization 

The controlled pollination method developed for Leucospermum has been 

extensively used in Protea hybridization (Brits 1983). The method entails covering the 

inflorescence of the female parent to exclude all possible pollinating fauna after removing 

any flowers with dehisced anthers. Two days later the unopened flowers are all removed 

from the center of the inflorescence, leaving a single ring of approximately 40 to 60 

89

flowers that are newly opened. The pollen from the pollen parent is applied by using a 

style with pollen on the pollen presenter as a “brush” applicator. The inflorescence is recovered. 

Mature achenes are harvested between nine and twelve months later. The achene 

set obtained by using this technique in Protea have been dismally small (Brits 1992), 

except in the case of intraspecific hybridization in P. cynaroides and P. repens (Table 

3.6). 

Table 3.6. Controlled hybridization results in Protea using the Leucospermum 

hybridization technique (Brits 1983). 

Female parent Male parents Average achene set (%) 

P. aristata 

P. compacta 

P. aristata, P. repens 

P. compacta, P. eximia, P. 

cv. Sylvia 

0 

1.2 

P. cynaroides P. cynaroides 20.4 

P. eximia 

P. eximia, P. eximia/P. 

compacta, P. repens 

0 

P. pudens 

P. repens, P. obtusifolia, P. 

cv. Ivy 

0 

P. repens P. repens 24.6 

Modifications to this technique have been made, using information gleaned from 

the studies of natural pollination. Firstly, it has been found that viable achenes are often 

found clustered on the involucral receptacle and this appears to be under direct control of 

the female plant (Wright 1994a,b; Mustart et al. 1995). Secondly, visual observation of 

the involucral receptacle indicates that space could be a limiting factor in achene 

development, similar to that observed in Banksia (Fuss and Sedgley 1991a,b). Therefore 

the pollination technique was modified so that at the first visit after bagging the 

inflorescence only 10 to 20 flowers are pollinated, with the removal of the next spiral of 

flowers. This is done repeatedly over three to four successive visits to pollinate flowers on 

the inflorescence, with a final visit to remove the central, remaining flowers. While very 

time consuming, the increase in success of obtaining mature, viable achenes makes the 

effort worthwhile (Table 3.7). 

The full scope of interspecific hybridization can only be utilized if pollen can be 

successfully stored for use on species or clones flowering at different times of the year. 

The pollen of four Protea species was successfully stored for 12 months, desiccated, 

either at –18°C in an ordinary household deep freeze or in liquid nitrogen (Van der Walt 

and Littlejohn 1996c). 

90 

D. Interspecific Hybridization 

Interspecific incompatibility can be exhibited at different stages during the 

reproduction process or in the interspecific hybrid plant. The simplest form of 

incompatibility takes place prior to fertilization, where pollen tube growth from a 

“foreign” species cannot grow down the style of the seed parent and no fertilization 

occurs (Van Tuyl 1989). Studies on P. repens and P. eximia indicated that the ten-fold 

decrease in achene set observed after interspecific pollination compared to intraspecific 

pollination was due to pollen tube growth being interrupted while growing down the style 

of the female parent (Van der Walt and Littlejohn 1996a). High correlation was observed 

between the number of flowers in which pollen tubes observed entered the ovule and the 

percentage achene set recorded. This indicates that in these two species, post fertilization 

mechanisms to inhibit interspecific hybridization were not active.

Table 3.7. Some successful cross combinations obtained in Protea by using the modified 

controlled pollination technique. 

Seed parent Pollen parent Achene set (%) 

P. aurea P. lacticolor/P. mundii 19 

P. neriifolia P. holosericea 9 

P. magnifica/P. laurifolia P. holosericea 20 

P. pudens P. acuminata 63 

P. pudens P. nana 27 

P. neriifolia/P. burchellii P. holosericea 8 

P. eximia P. compacta 16 

P. compacta/P. neriifolia P. repens/P. aristata 1 

P. lepidocarpodendron/P. P. magnifica/P. neriifolia 5 

neriifolia 

P. magnifica/P. laurifolia P. neriifolia 2 

P. lepidocarpodendron/P. P. laurifolia/P. magnifica 8 

neriifolia 

P. eximia/P. susannae P. compacta 5 

P. compacta P. compacta/P. burchellii 15 

P. compacta P. longifolia/P. burchellii 15 

P. burchellii P. compacta/P. burchellii 8 

P. magnifica/P. laurifolia P. magnifica/P. obtusifolia 1 

Incompatibility can also be detected in poor vigor and growth of interspecific 

hybrids. In general, interspecific hybrids in genus Protea are vigorous (Brits 1983). A 

further level of incompatibility is chromosomal incompatibility, leading to loss of sexual 

reproduction capacity in interspecific hybrids. Pollen grain infertility is a good indicator 

of meiotic disturbances during the development of the pollen grains (Van Tuyl 1989). In 

genus Protea the fertility of pollen ranges from 0% in the case of P. cynaroides 

interspecific hybrids to 89% in a P. laurifolia hybrid (Van der Walt and Littlejohn 

1996b). No pattern of relatedness between parental species and pollen fertility was 

detected. Pollen size varied significantly between and within species. Meiotic analysis of 

interspecific hybrids of Protea has not yet been done and is complicated by the small size 

of the chromosomes and the woodiness of the flowers. No differences in the basal 

chromosome number of 12 have been recorded between species (De Vos 1943). 

E. Cultivars 

The aim of a breeding program is to develop cultivars (see Table 3.5) suitable for 

commercial exploitation for cut flower production. Currently cultivars of genus Protea 

originate from three sources: selection of individual superior plants from within species, 

selection of chance hybrids (Plate 4), and selection from achenes obtained from controlled 

hybridization (Plate 5) (Table 3.8). The parentage of chance hybrids is deduced from 

knowledge of characteristics of taxonomic importance between the seed parent and 

possible pollen parents growing in the vicinity of the seed parent. 

Prior to 1973, commercial plant resources were undescribed and traded 

collectively under their old specific names, e.g., P. barbigera Meisn. for P. magnifica 

Link. In 1973 an international cultivar registration program for Proteaceae was launched, 

South Africa having obtained authority from the International Society for Horticultural 

Science to act as the International Registrar of all protea cultivars falling within the South 

African genera (Brits et al. 1983). Some of the well known Protea cultivars incorporated 

in the international register are listed in Table 3.5. 

91

Table 3.8. Examples of cultivars derived from different sources within genus Protea. 

Source Cultivar name Putative parentage 

Selection of superior 

plants within species 

Selection of chance 

interspecific hybrid 

92 

Fiery Duchess 

Atlantic Queen 

Snow Queen 

Cardinal 

King Grand 

Susara 

Selection derived from 

controlled pollination Madiba 

Clare 

V. PHYSIOLOGY 

P. eximia 

P. magnifica 

P. magnifica 

P. eximia/P. susannae 

P. cynaroides/P. grandiceps 

P. magnifica/P. susannae 

P. cynaroides/P. cynaroides 

P. cynaroides/P. cynaroides 

Protea exhibits some unique physiological traits, such as the role of roots in water 

and nutrient uptake and carbohydrate metabolism in the cut flowering stems. The 

understanding of many physiological processes is incomplete, but this provides a fertile 

area for continued research. 

A. Flowering 

Protea species growing in their natural habitat are observed to flower at distinct 

times of the year (see Table 3.3). The majority of commercially used Protea flower 

naturally during the autumn to spring months of the Southern Hemisphere. The high 

demand for flowers in Europe, the dominant market for South African Proteaceae, is mid 

spring to mid summer, a time when few species flower. This has resulted in studies aimed 

at elucidating how flowering is initiated and if it can be manipulated. 

The Protea stem grows in spurts (called flushes) during loosely defined growth 

periods during the year. This produces clearly defined growth flushes on the stem. Under 

the climatic conditions of the Western Cape, the predominant growth periods are: Winter 

(March to August), Spring (September to November), Summer (December to January), 

and Autumn (February to March) (Malan 1993). The number of flushes, ranging from 

none to two, produced during each growth period, is influenced by the environmental 

conditions and the species. The Protea inflorescence is borne terminally on a shoot 

consisting of two or more growth flushes. The flushes arise in succession from a distal 

axillary bud, with flushes exhibiting strong apical dominance during active growth. 

Inflorescence initiation in Protea cultivar Carnival, a putative hybrid between P. 

compacta and P. neriifolia takes place after cessation of growth of the spring or summer 

flush under conditions in the Western Cape, South Africa. Generally two or more 

successive flushes are required for an inflorescence to initiate (Greenfield et al. 1993). A 

spring flush must be subtended by at least one previous flush for flower initiation to take 

place. Although not investigated in other species or hybrids, the requirement for at least 

two growth flushes subtending a flower is likely to hold for all other species. In some 

species, such as P. neriifolia, flowers are produced on secondary growth flushes that 

initiate below the current flower head, during the same season. This appears to be species 

specific, and will only occur on flowering stems with a large diameter (G. M. Littlejohn, 

pers. obs.). A minimum diameter of the flush subtending the inflorescence, a possible 

requirement for flowering to take place, has not been determined for any of the Protea. 

There are indications that the sink capacity of the stem plays a role in the ability of a stem 

to initiate an inflorescence (De Swardt 1989). Pruning studies on Protea cv. Carnival 

have shown the possibility of manipulating the flowering time, stem length, and 

production of mature bushes by manipulating the pruning time (Gerber et al. 1993;

Hettasch et al. 1997). Pruning the plant during the early spring months results in no 

flowering in the following spring, probably due to limited leaf area. Inflorescences are 

initiated on the spring and summer flushes of the following year, resulting in peak 

flowering during February as opposed to normal peak flowering during April. The 

bearing cycle of the plant is transformed in this way from an annual cycle to a biennial 

cycle. This also allows each stem to develop more growth flushes, which results in longer 

stems and a greater marketable harvest. 

The precise environmental and intraplant factors triggering inflorescence initiation 

are still unclear. Dupee and Goodwin (1990a) observed flower initiation on the first 

spring flush in P. neriifolia cv. Salmon Pink, while seedlings of the Long Leaf variant of 

P. cynaroides initiated flowers on the summer flush as well as the autumn flush. The 

flowering time and number of flowers harvested from different Protea species changed, 

depending on the site at which they were planted (Dupee and Goodwin 1990b, 1992). A 

delay in flowering, of approximately six months, and a reduction in flower number 

occurred at the site with the highest altitude, lowest mean winter temperature and largest 

difference in day length between summer and winter. ‘Guerna’ produces only 18 flowers 

per bush during the period of December to February at 33° South, compared to 86 stems 

per bush at 21° North spread over twelve months of the year (Table 3.9). In other 

cultivars, differences in flower time and flower number per plant per annum occurred 

when grown in Hawaii or South Africa. While flower numbers can be accounted for by 

differences in soil fertility, the time of flowering appears dependant on differences in day 

length. It would appear that in the absence of clear environmental cues, such as changes 

in day length, many Protea produce a flower on a stem when sufficient carbohydrate 

source is available in the stem. This latter method is employed by ‘Sylvia’, a backcross of 

P. susannae on a hybrid between P. eximia and P. susannae (Malan and Le Roux 1995). 

Although ‘Sylvia’ naturally flowers during the late summer and autumn in South Africa, 

flowering over the full year can be obtained if pruning is scheduled to occur throughout 

the year. 

Table 3.9. Comparison of flowering times and flower yield of Protea cultivars grown in 

Hawaii (21°N, 900 m) and South Africa (33°S, 177 m ), with flowering season 

corrected to the Southern Hemisphere. 

Months Flowering 

Cultivar z Location y J F M A M J J A S O N D 

Flowers 

harvested 

Guerna Hawaii * * * * * * * * * * * * 86 

South Africa * * * 18 

Brenda Hawaii * * * * 210 

South Africa * * 20 

Cardinal Hawaii * * * * * * * * 31 

South Africa * * * * * * 35 

Red Baron Hawaii * * * * * * * * * * 86 

South Africa * * * 24 

Sylvia Hawaii * * * * * * * * * * * * 66 

South Africa * * * * * 38 

z 

Refer to Table 3.8 for parents. 

y 

Hawaii data based on Criley et al. (1996); South African data based on Littlejohn (unpublished). 

93


1. Sexual Reproduction. 

The fruits of the Protea species are held on the woody receptacle enclosed by the 

involucral bracts. The Protea species found in the savanna areas outside the Cape Floral 

Kingdom release their achenes between two and four months after flowering (Rebelo 

1995). The Eastern Ground and Western Ground Protea (Table 3.1) generally release 

their achenes one to two years after flowering. The remaining species store the achenes in 

the infructescence indefinitely, a process called serotiny. The achenes are subject to large 

variations in temperature and the infructescence may become waterlogged during heavy 

rains, but germination will only take place after the achenes fall to the ground (Rebelo 

1995). About 80% of viable achenes will germinate within 90 days, if kept sufficiently 

moist and at temperatures ranging from 5° to 25°C (Van Staden 1966). The duration from 

fertilization until harvest of achenes of Protea affects the germination rate and amount of 

achenes germinating (Van Staden 1978; Le Maitre 1990). Dormancy seems to be imposed 

by a low temperature requirement and by the action of the pericarp, which prevents 

simultaneous germination of all achenes (Deall and Brown 1981). Scarification, 

stratification, and incubation in pure oxygen improved the germination of P. compacta 

(Brown and Van Staden 1973). Treatment of P. compacta with Promalin, a solution 

containing GA4/GA7 and benzyladendine, increased germination, as did a stratification 

treatment of 60 days at 5°C, but treatment with GA3 reduced germination (Mitchell et al. 

1986). Rodríguez Pérez (1995) observed an improvement in germination after imbibition 

with GA3 in P. neriifolia and P. eximia, but no significant difference in P. cynaroides. 

The optimum cues for maximum germination are likely to differ between the Protea 

species, as has been observed in Leucospermum (Brits 1990c). 

2. Vegetative Propagation. 

Members of the Proteaceae can be propagated by vegetative cuttings. The 

selection of single plants for use as clonally propagated cultivars depends upon the ability 

to propagate the plant material vegetatively. Most commercial Protea species are 

propagated by using approximately 20 cm long terminal, semi-hardwood cuttings (Malan 

1993). Sub-terminal cuttings can be successfully used in some cultivars (Harre 1995) and 

may be the preferred type of cutting (Montarone et al. 1997). Sub-terminal cuttings of 

‘Sylvia’ and ‘Cardinal’ delivered more vigorous plantlets with improved branching 

complexity at an earlier age. Rooting of leaf bud cuttings is also possible in P. obtusifolia 

(Rodríguez Pérez 1992). In general a 5 sec basal dip in indole butyric acid at 1,000 to 

4,000 ppm is followed by setting the cuttings in well aerated medium with intermittent 

mist and bottom heat at 22° to 25°C (Malan 1993; Harre 1995). Rooting generally occurs 

within six to 16 weeks. Auxin concentration (Perry 1988), auxin carrier (Gouws et al. 

1990), and hormone mixtures (Criley and Parvin 1979; Gouws et al. 1990) all influence 

rooting success. Specific requirements have to be adapted for each cultivar for optimum 

results (Harre 1995). The frequency of misting (Perry 1988), bottom heat temperature, 

light intensity, and rooting medium aeration (Harre 1995) also affect rooting. The time of 

harvesting cuttings is important in Protea, where growth flushes are not always well 

synchronized (Malan 1993), because the physiological status of the new growth flushes 

may not be consistent. Scarring of the base of the cutting is effective in promoting rooting 

of some Protea cultivars (Rodríguez Pérez 1990). Control of diseases while plants are 

rooting is important to ensure success (Benic 1986) and includes proper sanitation in the 

mother plants. 

3. Grafting. 

Grafting of Protea has focussed on using alkaline tolerant P. obtusifolia as a 

rootstock (Brits 1990a,b). The most successful method is the grafting or budding onto 

cuttings. The cutting can be rooted or unrooted. With unrooted cuttings, rooting and graft 

union are achieved simultaneously in a mist propagation facility. This latter technique has 

94

een successfully applied to Leucadendron (Ackermann et al. 1997). Factors requiring 

more research in Protea grafting are ease of rooting of the rootstock and selection for low 

phenolic production in the rootstock and scion, or methods to control blackening of the 

cut surfaces (Brits 1990b). Low grafting success in Protea was not ascribed to 

incompatibility between scions and rootstock. An extensive search for rootstocks within 

Proteaceae resistant or tolerant to root rot caused by Phytophthora cinnamomi highlighted 

successful scion and rootstock combinations within the different genera and indicated 

combinations where graft incompatibility occurred (Moffat and Turnbull 1995). P. 

cynaroides grafted successfully onto a variety of Protea species, but graft union failure 

occurred after one to two years, with eventual death of the scion. The most successful 

rootstocks tested were Protea cultivar Pink Ice and P. roupelliae. 


Tissue culture techniques for propagation of Protea (Rugge 1995) have been 

developed. The major problem in genus Protea is the browning of the tissue due to 

phenolic compounds (Malan 1993), however, shoot proliferation has been obtained in P. 

repens, P. obtusifolia, and P. cynaroides. Successful transplanting of rooted shoots to soil 

has not been achieved. Callus and proteoid roots have been raised from mature cotyledons 

of Protea (Van Staden et al. 1981). 

B. Water and Nutrient Uptake 

Most species of Protea are adapted to nutrient-poor soils derived from Table 

Mountain Sandstone, with a pH (KCl) between 4 and 6 and a clay content of less than 

20%. P. obtusifolia is found only on limestone calcareous sands with a pH (KCl) as high 

as 8 and P. susannae on the fringes of the limestone areas with pH (KCl) in the region of 

6 to 7. P. laurifolia can be found on shale soils with a higher silt content. The two rare 

species, P. mucronifolia and P. odorata, are adapted to growing on shale derived soils 

(Rebelo 1995). 

The most striking adaptation of the Proteaceae to the nutrient-poor soils on which 

they are found is the presence of proteoid roots, first described by Purnell (1960). The 

root system of Protea consists of a deep tap root, primarily a root for sourcing water, and 

shallow, lateral roots in the upper five to 10 cm that bear clusters of proteoid roots. 

Proteoid roots are specialized lateral roots that are diarch, show limited growth, and do 

not undergo secondary thickening. They bear profuse root hairs that are ephemeral and 

sometimes branched. Under natural conditions they first appear on roots of seedlings 

about six months old when the cotyledons are just withering away. The proteoid roots 

enable the plant to efficiently extract soil phosphorus (Lamont 1982), nitrogen, and 

potassium (Vorster and Jooste 1986a,b). In Protea growing under seasonally dry 

conditions, such as their natural habitat, proteoid roots are seasonal structures. Proteoid 

and other roots are only formed during the wet season (Lamont 1983). Shoot growth is 

predominantly during the dry, warm season. High nutrient levels in the soil, especially 

phosphates, inhibit the formation of proteoid roots in many of the Proteaceae (Grose 

1989; Silber et al. 1997). Proteaceae are also characterized by highly efficient utilization 

of P within the plant (Grundon 1972; Grose 1989). The use of tissue and soil samples to 

determine the seasonal nutritional requirements has not been entirely successful (Parvin 

1986). Seasonal and interplant differences in the cycle of growth flushes makes 

interpretation of leaf samples difficult (Barth et al. 1996). Leaf nutrient composition for 

‘Pink Ice’ was studied in detail and the results are summarized in Table 3.10. The range 

in nutrient concentrations is given for the two periods of the year, i.e., mid summer and 

late autumn through winter, when the variation between samples and plants was the least. 

Significant positive and negative correlations were observed between nutrients, e.g., N 

concentrations were positively correlated with P, K, Na, and Zn and negatively correlated 

with Ca, Mg, and Fe concentrations. These significant relationships may indicate 

synergistic and antagonistic interactions between nutrients that need to be considered 

95

when interpreting plant nutrient data. 

Research effort has focused on the cultivation of Protea in soilless media 

(Montarone and Allemand 1993). This has led to clarification of the total plant uptake of 

nutrients for certain species and clones (Montarone and Ziegler 1997). It is obvious that 

differences between species exist in terms of their requirements for different nutrients 

(Claassens 1986). 

Table 3.10. Range in mean nutrient concentrations of leaf samples of Protea cultivar Pink 

Ice during two periods of the year z . 

96 

Nutrient December to February May to August 

(% dry weight) 

N 0.82–0.83 0.77–0.86 

P 0.06–0.07 0.05–0.06 

K 0.37–0.41 0.18–0.21 

Ca 0.46–0.51 0.63–0.68 

Na - 0.14–0.18 

S 0.11–0.13 0.09–0.10 

(mg/kg) 

Cu - 3.5–4.5 

Zn 12–15 - 

Mn 43–44 - 

Fe - 51–54 

z Data from Maier et al. (1995). 

Water requirements of the different species grown under soilless conditions differ 

(Montarone and Ziegler 1997), with P. cynaroides requiring twice the amount of water 

required by P. eximia. Water requirements can be deducted by knowledge of where 

species grow naturally, i.e., species growing in wet valleys or near water sources have 

higher water requirements than species preferring dry areas (Manders and Smith 1992). 

Protea, however, will not grow under waterlogged conditions (Vogts 1989). 

Investigations on the water requirement of cultivated Protea under irrigation 

indicated that maintenance of a high soil water capacity was essential to the field survival 

of rooted cuttings of the Protea cv. Cardinal (Van Zyl et al. 1999). Active consumption of 

water continued throughout the year and maintenance of high soil water levels increased 

the shoot lengths and biomass production on cultivar Cardinal in comparison with lower 

soil water levels. 

C. Postharvest Physiology 

In the genus Protea, vase life reduction is associated with the phenomenon of leaf 

blackening due to oxidation of phenolic compounds in the leaves (McConchie et al. 

1991). The vase life of Protea is generally three to four weeks, but postharvest leaf 

blackening reduces the vase life to approximately one week. 

Discoloration of Protea leaves can be induced by mechanisms such as pre-harvest 

mechanical damage, insect or fungal attack, or excessive heat; however, postharvest leaf 

blackening occurs on leaves without any physical damage (Jones et al. 1995). Although 

pre-harvest conditions such as waterlogging, drought, and harvesting stems from aged 

plants have been reported to affect the extent of leaf blackening (De Swardt 1979), little is 

known of the possible mechanisms involved. 

Symptoms of leaf blackening occur within 2 to 5 days after harvest in P. eximia 

and P. neriifolia (McConchie et al. 1991). The extent of leaf blackening varies widely

etween species (McConchie and Lang 1993), clones within species (Paull and Dai 

1989), and the time of year. Paull and Dai (1989) found a reduction in leaf blackening if 

inflorescences were harvested in the afternoon compared to the morning and if 

inflorescences were harvested when the involucral bracts had just opened rather than at 

the soft bud stage. Fumigants used for insect disinfestation of inflorescences after harvest 

can also increase leaf blackening (Coetzee and Wright 1990; Karunaratne et al. 1997). 

Removal of the inflorescence significantly delays the onset of leaf blackening 

(Reid et al. 1989; Dai 1993). The inflorescence continues to expand after harvest and 

exhibits a high rate of respiration (Ferreira 1986) with a large volume of nectar 

production when open (Cowling and Mitchell 1981). Removal of the inflorescence, 

girdling of the stem just below the inflorescence (Dai 1993; Reid et al. 1989), adding 

2.5% to 5% of sucrose to the vase solution (Dai 1993), or placing the floral stems in 

bright light (Reid et al. 1989) delays or even prevents leaf blackening. The starch and 

sucrose concentration in leaves declines in stems held in the dark rather than in the light 

(McConchie et al. 1991; Bieleski et al. 1992). 

The physiological basis of leaf blackening is still poorly understood. It appears to 

be a complex cascade of events that lead to the oxidation of phenolic compounds (Jones 

et al. 1995). This occurs, either enzymatically via polyphenol oxidase or peroxidase, or 

non-enzymatically after cleavage of phenolic glycosides by glucosidases. It is still not 

clear if membrane degradation occurs during leaf blackening (Jones et al. 1995). A 

reduction in leaf carbohydrate levels is coincident with leaf blackening. Dai and Paull 

(1995) concluded that leaf blackening in Protea is a result of depletion of carbohydrate by 

the inflorescence. This was due primarily to the sugar demand for nectar production. 

VI. PRODUCTION 

A. Cultivation 

Cultivation techniques, describing the basic cultivation practices in different 

regions of the world, have been published in books by Matthews (1993), Vogts (1989), 

and Harre (1995). The Agricultural Research Council of South Africa has compiled a 

handbook on cultivation of Proteaceae (1998). 

The cultivation of Protea is limited by the availability of suitable soils and 

climatic conditions (Vogts 1989). The soils must be well drained and acidic, except in the 

case of lime tolerant species such as P. obtusifolia. Clay content less than 20% is 

preferred, but up to 50% clay will be tolerated by some species as long as the drainage is 

excellent. Hot, humid conditions are not well tolerated by Protea and sufficient air 

movement is required for healthy growth. High light intensity is required. Protea are 

generally cultivated without protection and in open soil. In South Africa, two forms of 

cultivation are practiced: intense cultivation of clonal and seed material in rows, and 

broadcast seed sowing. The latter is used primarily for P. repens and other species used in 

the dried flower industry (Coetzee and Littlejohn 1995). Cultivation under glass in 

soilless media is possible (Montarone and Allemand 1993) and is considered 

economically viable in the south of France. 

The general recommendation is to use a between row spacing of 3.5 to 4.0 m and a 

within row spacing of 0.8 to 1.0 m, giving a plant density of 2,500 to 3,560/ha. In 

practice, much closer spacing, with plant densities of up to 6,000/ha, is used by many 

farmers. The most important factors determining plant spacing are the size of the farm 

implements available to the farmer and the size of the plantation. In plantations small 

enough to be managed with hand labor only, plants are more closely spaced, but in large 

plantations wide inter-row spacing is required for the mechanical equipment. Soil 

preparation prior to planting depends on the soil type and depth. In very shallow soils, 

ridging is recommended to improve the depth of soil available for plant growth. Ridging 

is also used to improve the drainage of heavy soil. In very rocky soil, or on very steep 

97

slopes, no soil preparation is done. In soils of a good depth, liming and adjustment of the 

macro and micro nutrient levels by fertilization prior to soil preparation to a depth of 1 m 

is recommended. 

Drip irrigation is the preferred method of supplying water to Protea during the dry 

season. Overhead irrigation is not suitable as it increases the possibility of diseases and 

large droplets can damage the flower heads and leaves. The Protea species and hybrids 

used in cultivation will tolerate dry summer periods, but sensitivity to lack of water 

during the winter varies, e.g., P. repens will tolerate dry winter conditions in a summer 

rainfall area, but P. stokoei will not. Inorganic and organic mulches are widely used. The 

choice of the type of mulch depends on the soil type, soil temperatures, and cost of the 

mulch. Low growing cover crops that have a low cutting frequency are recommended 

between rows to assist in weed control. Fertilization programs differ from locality to 

locality, depending on the chemical and physical properties of the soil, the biomass 

removed annually from the plants during harvest and pruning, and the cultivar being 

grown. The general recommendations are not to apply large amounts of phosphates, nor 

use fertilizers in which more than 50% of the nitrogen is bound in nitrates. Top-dressing 

with potassium during the life of the plant will be necessary. 

Maintenance of the immature bushes requires pruning to develop a complex 

structure of bearers as soon as possible. Under conditions where the plants grow slowly, 

annual pruning is sufficient, but in warmer areas where plants grow faster, pruning will be 

required two to three times a year during the first two years. Protea cultivars are generally 

able to bear a harvest of flowering stems of sufficient length two to four years after 

planting, depending on the parentage of the cultivar. Bushes in production will be pruned 

to leave bearers for the following crop during the harvest of flowering stems, with 

additional pruning to remove unwanted vegetative stems as required. Pruning to achieve 

biennial production requires leaving a long bearer when the flowering stems are 

harvested. This long bearer is then re-cut during the early spring to remove any new 

shoots, thereby timing the initiation of the new shoots correctly for manipulation of the 

flowering time. The number of bearers, and therefore shoots per plant, at any stage of the 

plant’s development is dependent on the cultivar and its interaction with the climatic and 

soil conditions. 

Flowering stems are harvested at any stage between soft-bud, or anthesis of the 

outer ring of florets (Plate 6). The stems are best placed immediately in water, with 

cooling to 2° to 5°C within 60 minutes after harvest. Thereafter the cool chain should be 

maintained until the stems are sold to the florist or consumer. In exporting countries the 

cold chain is of necessity broken during air transport. The stem length categories for 

export standards from South Africa start at a minimum of 40 cm, with an increase in 

length of 10 cm for the next category. The stem length of the longest and shortest stem 

packed in a carton may not differ by more than 5 cm and the stem may not deviate by 

more than 5 cm from straight. The Protea with small flower heads, such as P. nana, may 

be exported from 25 cm in length and longer. Maximum allowable blemishes, either 

physical or due to disease, on the involucral bracts and leaves are also defined, but each 

importing country sets its own phytosanitary restrictions. 

The cultivation of Protea, both within its natural habitat and in other regions is 

increasing annually (Middelmann and Archer 1999). Species such as P. cynaroides grow 

under a wide variety of conditions, but other species, such as P. compacta and P. 

magnifica, grow poorly when cultivated outside their natural habitat range. The 

interspecific hybrids registered as cultivars (Table 3.5) are generally easily cultivated 

under a diversity of conditions. 

98 

B. Pathogens Associated with Diseases of Protea 

There are a number of unique pathogens associated with Protea species, as well as 

some wide host range pathogens that attack these plants. References are also made to 

fungi that attack proteas when they are cultivated outside their natural habitat (Forsberg

1993; Ziehrl et al. 1995; Swart et al. 1998; Swart 1999). The first protea disease was 

described by Cooke (1883) and since then more than 30 pathogens have been isolated 

from Protea, of which nine can be considered as economically important diseases of 

Protea species (Table 3.11). Diseases are one of the limiting factors in the 

commercialization of proteas. Diseases can lead to the total destruction of cultivated 

proteas. Infected foliage and/or stems of protea flowers are esthetically not acceptable and 

lead to phytosanitary problems during international trade. In the past, disease resistance 

was not taken into account with cultivar development, as selections were primarily aimed 

at flower characteristics (Knox-Davies et al. 1986). As a result epidemic disease problems 

can occur with intensive cultivation of clonal proteas. 

The most important diseases of Protea species can be grouped into root diseases, 

leaf spot diseases, diseases of the shoots, stem and inflorescence, and the cankers. With 

the exception of one bacterial disease, all of these diseases are caused by fungi. There 

have been no confirmed reports of Protea infected by viruses. 

1. Pathogens of Roots. 

Phytophthora cinnamomi is an important root pathogen of Proteaceae in Australia 

(Forsberg 1993), New Zealand (Greenhalgh 1981), South Africa (Knox-Davies et al. 

1986), and the U.S.A., especially Hawaii (Kliejunas and Ko 1976; Rohrbach 1983). The 

disease causes root and crown rot, and is commonly referred to as the sudden death 

syndrome. Infected plants become chlorotic and wilt as a result of extensive root rot (Von 

Broembsen 1979, 1989; Cho 1981). Most protea deaths occur during hot dry periods and 

on badly drained soils (Newhook and Podger 1972; Pegg and Alcorn 1972; Van Wyk 

1973b). 

Table 3.11. Economically relevant diseases of Protea species. 

Pathogen Name of Disease Reference 

Phytophthora cinnamomi 

Rands 

Root and crown rot (Van Wyk 1973a) 

Batcheloromyces proteae 

P.S. Van Wyk and Knox- 

Dav. 

Leaf spot (Marasas et al. 1975) 

Coleroa senniana (Sacc.) Leaf spot (Saccardo 1910) 

Müller & Arx 

Leptosphaeria protearum Leaf spot (Van Wyk 1973a) 

Syd. and P. Syd. 

Mycosphaerella proteae Leaf spot (Van Wyk 1973a) 

Sacc. 

Mycosphaerella 

jonkershoekensis P.S. 

Van Wyk, Marasas and 

Knox-Dav. 

Leaf spot (Van Wyk et al. 1975a,b) 

Phyllachora proteae Wakef. Leaf spot (Wakefield 1922) 

Botrytis cinerea Pers: Fr. Flower head blight (Serfontein & Knox-Davies 

1990b) 

Collectotrichum 

Anthracnose/tip die-back (Benic & Knox-Davies 

gloeosporioides (Penz.) 

Penz. and Sacc 

1983) 

Armillaria luteobubalina 

Watling and Kile 

Root pathogen (Forsberg 1993) 

Fusarium oxysporum 

Schltdl.: Fr. 

Fusarium wilt (Swart et al. 1998) 

Macrophomina phaseolina Root and collar rot (Benic 1986) 

99

(Tassi) Goid. 

Phytophthora nicotianae 

Breda de Haan 

Root and collar rot (Forsberg 1993) 

Rhizoctonia solani J.G. 

Kühn 

Damping-off (Rohrbach 1983) 

Rosellinia De not. sp. Basal stem, crown or collar 

rot and root rot 

(Forsberg 1993) 

Verticillium dahliae Kleb. Shoot wilting and chlorosis 

of foliage 

(Forsberg 1993) 

Pythium vexans De Bary Damping-off (Benic 1986) 

Pseudomonas syringae Bacterial leaf spot (Paine and Stansfield 1919) 

100 

Moffatt 

Cercostigmina protearum 

(Cooke) U. Braun and 

Crous var. protearum 

Clasterosporium proteae 

M.B. Ellis 

Coniothyrium Corda emend. 

Sacc. Species 

Mycosphaerella bellula 

Crous and M.J. Wingf. 

Teratosphaeria fibrillosa 

Syd. and P. Syd. 

Leaf spot (Crous and Braun 1996) 

Leaf spot (Ellis 1976) 

Leaf tip disease (Van Wyk 1973a) 

Leaf spot (Crous and Wingfield 1993) 

Leaf spot (Sydow and Sydow 1912) 

Teratosphaeria proteaearboreae 

P.S. Van Wyk, 

Marasas and Knox-Dav. 

Leaf spot (Van Wyk et al. 1975a) 

Trimmatostroma macowanii Leaf spot (Ellis 1976) 

(Sacc.) M.B. Ellis 

Didymosporium congestum Leaf spot (Diodge 1950) 

Syd. 

Dothiorella Sacc. sp. Leaf spot (Anon. 1991) 

Chondrostereum purpureum Silver leaf (Forsberg 1993) 

(Perd.: Fr.) 

Schizophyllum commune Trunk rot (S. Denman, pers. comm.) 

Fr.: Fr. 

Sclerotinia Fuckel. sp. Die back (Benic 1986) 

Phomopsis (Sacc.) Sacc. sp. Die-back (Orffer and Knox-Davies 

1989) 

P. cinnamomi can be isolated from seedlings with damping-off symptoms in 

seedbeds and from cuttings in nursery beds (Benic 1986; Forsberg 1993). Symptoms are 

generally less severe and develop more slowly on Protea than on other Proteaceae such as 

Leucospermum and Leucadendron. Protea cynaroides, P. neriifolia, and P. repens appear 

to be resistant to P. cinnamomi. Other soil-borne pathogens of Protea are listed in Table 

3.11. 

2. Pathogens of Leaves. 

Protea species are generally more prone to leaf spot diseases than other 

Proteaceae (Van Wyk 1973a) and the only bacterium, Pseudomonas syringae, was 

isolated from the leaves of P. cynaroides in England (Paine and Stansfield 1919) and 

Australia (Wimalajeewa et al. 1983). Bacterial leaf spot has not been recorded in South 

Africa (Knox-Davies et al. 1986). 

Batcheloromyces proteae Marasas is one of the economically important pathogens 

of Protea leaves. The leaf spots are not destructive but decrease the quality of the leaves

for commercial use. The most typical lesions are black, with a red-brown to purple-black 

discoloration of the leaf tissue (Marasas et al. 1975). The host range includes the 

following economically important proteas, P. cynaroides, P. grandiceps, P. magnifica, P. 

neriifolia, P. punctata, and P. repens (Marasas et al. 1975; Smith et al. 1983; Van Wyk et 

al. 1985; Knox-Davies et al. 1986; Swart 1999). 

Coleroa senniana was first described by Saccardo (1910) on leaves of P. gaguedi 

(P. abyssinica) from North Africa. The fungus commonly occurs on leaves of Protea 

species in Southern Africa (Doidge 1941) and is, except for Mycosphaerella proteae, 

probably the most widespread pathogen of Protea species. C. senniana produces tiny 

black specks (pseudothecia of the fungus) on the upper surface of Protea leaves. On P. 

magnifica the specks are yellow to brown (Van der Byl 1929; Serfontein and Knox- 

Davies 1990a). Coleroa senniana occurs on leaves of summer and winter rainfall Protea 

throughout sub-Saharan Africa (Saccardo 1910) and was also isolated on cultivated 

Protea in California, U.S.A. (Swart 1999). 

Leptosphaeria protearum causes leaf spots that are necrotic and sunken, with 

raised, dark brown margins (Van Wyk 1973a). Most economically important proteas are 

affected by L. protearum, but P. mag nifica is particularly susceptible. Leptosphaeria 

protearum appears specific to Protea species (Von Broembsen 1989). 

Mycosphaerella proteae is the most common pathogen on Protea species in South 

Africa (Van Wyk 1973a) and the host range includes winter and summer rainfall proteas 

(Saccardo 1891; Sydow and Sydow 1914; Doidge 1921; Van Wyk et al. 1975a,b; Swart 

1999). The leaf spots caused by M. proteae on the different hosts are quite variable in 

appearance but the spots are amphigenous and bright red-purple to red-brown. 

Mycosphaerella jonkershoekensis has so far only appeared on P. repens and P. magnifica 

(Van Wyk 1973a; Van Wyk et al. 1975a,b) and causes greyish to light brown leaf spots 

with raised, dark brown margins. Phyllachora proteae lesions are typically necrotic with 

a raised margin and move from the leaf tip inwards and finally cover the entire leaf 

surface (Wakefield 1922; Van Wyk 1973a; Van Wyk et al. 1975a). The host range 

includes P. acaulis, P. magnifica, P. neriifolia, and P. repens (Van Wyk 1973a; Van Wyk 

et al. 1975a). Van Wyk (1973a) stated that Phyllachora proteae must be reclassified as a 

species of Botryosphaeria. P. proteae has been reclassified as Botryosphaeria proteae 

Wakef. Denman & Crous. (Denman et al. 1999). 

Vizella interrupta G. Winter, S. Hughes causes brown lesions on Protea leaves, 

which often coalesce. The ascocarps form black spots on slightly discolored leaf tissue on 

Protea species. The host range includes P. cynaroides, P. grandiceps, P. magnifica, and 

P. neriifolia (Van Wyk 1973a; Van Wyk et al. 1975b, 1976; Swart 1999). 

3. Pathogens of Shoots, Stems, and Inflorescences. 

Colletotrichum gloeosporioides, or colletotrichum die-back, is the most important 

disease of Protea species (Coetzee et al. 1988). The die-back of young shoot tips is the 

most characteristic symptom. Other symptoms include necrotic stem and leaf lesions, 

stem rot, sunken stem cankers, seedling damping off, seedling blight, and cutting die-back 

(Von Broembsen 1989; Forsberg 1993). Colletotrichum lesions on one side of the stem 

cause the new growth to bend. This is referred to as shepherd’s crook disease of proteas. 

All economically important Protea species are affected by colletotrichum die-back in 

South Africa, Australia, and Hawaii (Greenhalgh 1981; Benic and Knox-Davies 1983; 

Benic 1986; Knox-Davies et al. 1986; Anon. 1991). 

Botrytis cinerea causes blight of the flowering branches and inflorescence heads. 

In Protea species, B. cinerea is a strong, active pathogen that can invade actively growing 

tissues and inflorescences (Rohrbach 1983). Brown spots develop on the leaves and 

inflorescence buds. The lesions expand and inflorescence buds can be killed, with 

necrosis extending down the inflorescence stalks, causing death of affected parts and new 

shoots (Serfontein and Knox-Davies 1990b; Forsberg 1993). Infected shoot tips collapse, 

darken, and die. Bending of affected shoots is typical of botrytis damping-off (Forsberg 

1993) and has been recorded on cuttings showing die-back symptoms (Benic 1986). The 

101

host range includes P. cynaroides and P. repens in South Africa and Hawaii (Swart 

1999). 

4. Pathogens of Woody Stems. 

Botryosphaeria species that cause cankers and die-back of injured tissue are a 

common problem and cause considerable losses in the production of Protea cut flowers. 

The most important species associated with Protea are Botryosphaeria dothidea (Moug.: 

Fr.) Ces and De Not., or Botryosphaeria ribis (Tode: Fr.) Grossenb. and Duggar. The host 

range includes P. compacta, P. cynaroides, P. eximia, P. grandiceps, and P. repens (Van 

Wyk 1973a; Knox-Davies et al. 1981; Swart 1999). 

In South Africa, only two chemicals are registered for the control of diseases on 

proteas. Looking at the complexity of the proteaceous pathogens, as well as the lack of 

control strategies of the diseases, it becomes evident that diseases are the most limiting 

factor in the commercialization of proteas. To prevent the development of diseases, the 

breeding and selection of resistant or tolerant cultivars will play an important role in the 

future. 

102 

C. Phytophagous Insect Fauna of Protea 

From studies on the insect guilds of P. repens (Coetzee and Latsky 1986), P. 

cynaroides and P. neriifolia (Coetzee 1989), P. magnifica and P. laurifolia (Wright 

1990), and P. nitida (Visser 1992), it is clear that proteas harbor a rich and distinct 

entomofauna. Insects associated with Protea species play an important ecological role as 

pollinators (Coetzee and Giliomee 1985), folivores (Wright and Giliomee 1992), and seed 

predators (Myburg and Rust 1975). Protea insects of significant economic importance 

can be divided into flower visitors, endophagous or borers, folivorous insects, and sapsuckers. 

1. Flower Visitors. 

The nectar and pollen rich protea flower attracts more than 200 insect species 

(Gess 1968) with, in many cases, high population levels (Visser 1992). Sugar birds like 

Promerops cafer (Mostert et al. 1980) and rodents (Cowling and Richardson 1995) 

pollinate proteas and it is also possible for insects to successfully pollinate Protea species 

(Coetzee and Giliomee 1985). Collins and Rebelo (1987) suggested that bird pollinated 

seed would be of genetically higher quality than seeds resulting from insect pollination, as 

birds have a larger foraging range and this could result in greater heterozygosity. Insects 

pollinating Protea species are generalist flower visitors and it is possible that larger 

beetles (Coleoptera, Scarabaeidae) may be more important pollinators than smaller insects 

(Wright 1990), again due to the greater mobility of larger insects. The presence of insects 

in cut flowers is one of the most serious limiting factors influencing the South African 

protea industry (Wright and Saunders 1995). Research on the use of a negative pressure 

fumigation system, based on a forced cooling system, provided excellent insect control 

using dichlorvos aerosol (Wright and Coetzee 1992; Wright 1992). 

2. Borers. 

Inflorescences and infructescences of Protea species are attacked by the larvae of 

a range of insects (Coetzee and Giliomee 1987a,b). The endophagous predators of 

serotinous protea seed are listed in Table 3.12. Insect seed predation of canopy stored 

Protea seed banks may be a factor that reduces the potential of proteas to form 

monospecific stands (Wright 1994b). Borers attacking Protea infructescences are also an 

important guild of pests of cultivated Protea, attacking young shoots and flower buds 

(Myburg and Rust 1975). On P. cynaroides, the larvae of the protea butterfly, Capys 

alphauses, has been recorded destroying up to 40% of the flower buds. Endophagous 

larvae cause phytosanitary problems, when present in cut flowers. Infested 

infructescences serve as a reservoir where pest numbers can increase and orchard

sanitation is a practice that should be applied to reduce borer incidence (Coetzee et al. 

1988). 

Table 3.12. Endophagous insects of Protea species. 

Genus Species Family Order 

Sphenoptera Buprestidae Coleoptera 

Genuchus G. hottentottus 

(Frabricius) 

Scarabaeidae Coleoptera 

Euderes E. lineicollis 

(Wiedemann) 

Curculionidae Coleoptera 

Capys C. alphaeus Lycaenidae Lepidoptera 

(Cramer) 

Orophia O. ammopleura Oecoporidae Lepidoptera 

(Meyrick) 

Argyroploce Torticidae Lepidoptera 

Bostra B. conspicualis Pyralidae Lepidoptera 

Warren 

Tinea Tineidae Lepidoptera 

3. Folivorous Insects. 

As the foliage of protea cut flowers must be esthetically acceptable, the leaves 

must be free of insect damage. Leaves of proteas are attacked by herbivores, leafminers, 

and gall forming insects. Leaf feeders can remove 5% to 22% of the leaf surface (Coetzee 

1989; Wright and Giliomee 1992). Leaf miners cause scarring of leaves, which renders 

the final product unmarketable, while gall forming insects are a phytosanitary risk 

(Wright and Saunders 1995). Young protea leaves are protected by a range of unique antiherbivore 

mechanisms such as phenolic compounds (tannins) and a pronounced 

cyanogenic capacity. Some species cover their young leaves with a thick layer of 

trichomes. This strategy has led to insects avoiding the more succulent and nutritious 

young leaves in favor of older, tougher leaves (Coetzee et. al. 1997). However, some of 

the most important herbivores on Protea species (Bostra conspicualis Warren, Pyralidae, 

Lepidoptera, and Afroleptops coetzeei) (Oberprieler), Curculionidae, (Coleoptera), have 

alimentary tract pH levels which suggest adaptation to a tannin rich diet (Wright and 

Giliomee 1992), which allows them to utilize older leaves in spite of the presence of 

tannins. Leafminers on Protea species are a guild of micro-lepidoptera that have 

successfully overcome the defense mechanism of young Protea leaves. The microlepidoptera 

belong to the families Phyllocnistidae, Incurvanidae, and Gracillaniidae. Only 

Proteaphagus capensis (Scoblein), Incurvariidae, found on P. cynaroides has been 

identified. The rest are still unknown and very little is known about their life cycle. Gall 

insects that belong to the Psyllidae (Hemiptera) can form galls on leaves of P. repens and 

cause phytosanitary problems. 

4. Sap Suckers. 

A selection of sap suckers feed on proteas. These can transfer diseases by means 

of their mouth parts, but cause little physical damage. Stressed plants can die when 

infestations are not controlled. Sedentary sap suckers include mealy bug 

(Pseudococcidae) and scale insect species of the Coccidae and Diaspididae (Coetzee 

1989), which causes phytosanitary problems with the export of flowers. 

Insects cause serious problems where proteas are cultivated in their natural habitat. 

Where proteas are cultivated outside their natural habitat, no serious insect problems have 

103

een experienced. This indicates that insects cannot easily overcome the defense 

mechanisms of the genus Protea. 

VII. CONCLUSION 

Protea have become an established horticultural crop, with a world sale of 

approximately 8 million flowering stems. In South Africa 3.01 million stems are 

exported, 1.14 million sold through the formal market, and 1.01 million sold by the 

informal sector. Other producing countries do not have figures for sales of Protea, but 

total sales are estimated at 3.00 million. Less than 1.5 million stems are sold through the 

Dutch auction system annually. The total share of the world flower market filled by 

Protea is very small, but it is the flower identified with South Africa. P. cynaroides is the 

national flower of South Africa and is the symbol of its sports teams. In the Cape Floristic 

Region, Proteaceae is an important component of the agricultural sector and the industry 

provides many job opportunities. Cultivation in areas outside their natural habitat has 

increased dramatically, both within South Africa and in other countries with similar 

climate and soil conditions. This has led to large quantities of proteas on the international 

market originating from regions other than the endemic environment from which Protea 

originate. Thus the Cape region and the people who initiated the protea industry run the 

risk of losing their market share. The stipulations of the Convention on Biological 

Diversity, which focus on benefit sharing related to commercial exploitation of genetic 

resources, would appear to have no practical application to the Protea genetic material. 

Protea species propagation material is widely available from around the globe. The 

majority of the most widely used cultivars originate in South Africa, but practical and 

financially viable methods of ensuring that royalties are returned to the legal owners of 

cultivars are insufficient. Solutions to this problem are being sought. 

An interesting pattern in the development of the indigenous cut flower industry in 

South Africa is that changes in the industry have most often been preceded by research 

activities. The challenge for South Africa is to produce high-quality blooms for the 

Western European market during the hot dry summer months. The majority of the Protea 

bloom during the early winter to late spring, while the Western European markets buy 

Protea during their Northern Hemisphere winter period from September to May. 

Selection and breeding has resulted in cultivars that flower in the summer, but more types 

are needed. It is also necessary to develop cultivars of similar appearance, but successive 

flowering periods, to provide a continuous supply of blooms to the market. An increase in 

the cultivation of the winter flowering species in the Northern Hemisphere could 

negatively impact on the Southern Hemisphere countries. Leaf blackening remains a 

problem in all regions where Protea are grown. Leaf blackening reduces the appeal of 

Protea to the consumer. It may be possible to reduce leaf blackening by genetic 

manipulation. If cultivars with reduced potential for leaf blackening can be developed, it 

would impact positively on the industry. 

There are pests and diseases of Protea that are common to the different regions in 

which they are cultivated. South Africa has the challenge of cultivating Protea in their 

natural habitat, with all the co-evolved insects and pathogens present in the natural 

fynbos. It is necessary to continuously research chemical and biological control measures. 

Environmentally sound practices must include the breeding of disease resistant cultivars 

to reduce the dependence on chemical control. 

Refinement of cultivation practices, such as pruning, fertilization, and irrigation, is 

required to maintain the economic return of Protea as a crop and to ensure the delivery of 

quality blooms to a very competitive international market. The challenges of cultivating 

Protea differ from region to region, but the basic plant physiology controlling the plant’s 

reaction to environmental stresses remains the same. Funding for basic research has, in 

the past, been generously supplied by government organizations, but in the economic 

climate of the late 1990s, government support of research is dwindling. This is especially 

104

true in South Africa, where flowers in general are still minor crops. 

The international flower markets are always searching for new, exciting products. 

Protea can fulfill this demand. A larger variety of cultivars, with different forms and 

colors, longer vase life, exceptional quality, and extended availability during the year are 

needed to maintain and increase the market share. These goals will only be achieved by 

continued research. 


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insects in Protea species (Proteaceae). Oecologia 99:397–400. 

Wright, M. G., and J. H. Coetzee. 1992. An improved technique for disinsectation of 

Protea cutflowers. J. S. Afr. Soc. Hort. Sci. 2:92–93. 

Wright, M. G., and J. H. Giliomee. 1992. Insect herbivory and putative defence 

mechanisms of Protea magnifica and P. laurifolia (Proteaceae). Afr. J. Ecol. 30:157– 

168. 

Wright, M. G., and M. D. Saunders. 1995. Protea plant protection: From the African 

context to the international arena. Acta Hort. 387:129–137. 

Wright, M. G., D. Visser, J. H. Coetzee, and J. H. Giliomee. 1991. Insect and bird 

pollination of Protea species of the western Cape: Further data. S. Afr. J. Sci. 87:214– 

215. 

Ziehrl, A., I. Pascoe, and I. Porter. 1995. Elsinoë scab disease and the Australian industry. 

Australian Protea Grower, Sept. 1995. 

112

Leucadendron: A Major Proteaceous 

Floricultural Crop ∗ 

Horticultural Reviews, Volume 32, 

Edited by Jules Janick 

ISBN 0-471-73216-8 © 2006 John Wiley 

& Sons 

by: Jaacov Ben-Jaacov and Avner Silber 

∗ The authors thank the many protea specialists—botanists, horticulturists, nurserymen, 

and farmers—for sharing with us their personal knowledge and experience in the 

preparation of this review. 

4 

113


Many members of the Proteaceae are being used as fresh and dry cut flowers 

(Plate I and II). Some of these crops have been reviewed recently: Leucospermum (Criley 

1998), Protea (Coetzee and Littlejohn 2001), and Banksia (Sedgley 1998). Recent 

publication on cultivation and diseases of Proteaceae are reviewed by Crous et al. (2004). 

The total number of Proteaceous cut stems around the world is about 100 million 

(Littlejohn 2001), and leucadendrons probably account for at least half of this total. Israel 

alone produces more than 35 million branches annually–about 25% of all the cut foliage 

exported from this country (Gazit 2002). All leucadendrons provide good cut foliage, but 

one of them, L. ‘Safari Sunset’, a Leucadendron hybrid developed some 40 years ago in 

New Zealand, is the most popular (Matthews 2002). This single cultivar accounts for 

about 90% of the proteas produced in Israel. Most of the scientific research on 

Leucadendron in Israel, especially with regard to commercial cultural practices, has 

addressed this cultivar. 

Proteas, including leucadendrons, have been investigated and cultivated for over 

250 years (Knight 1809; Linnaeus 1753) and still there are many myths regarding their 

uniqueness and thus their very special methods of cultivation. In fact, there is still 

relatively little solid, scientifically based information available on these plants. Three 

types of information have been consulted for this review: (1) scientific and technical 

publications; (2) books about proteas, some written for amateur botanists and nature 

lovers (Vogts 1982; Eliovson 1983; Rebelo 2001; Matthews and Carter 1983) and other 

books for commercial growers (Parvin and Criley 1991; Matthews 1993; McLennan 

1993; Harre 1988, 1991; Salinger 1985; Matthews 2002); and (3) published and 

unpublished accounts of practical experience, provided mainly by Israeli farmers, 

extension specialists, and researchers. In general, for simplification, the name “protea” 

will be used, in this review, for all plants belonging to the Proteaceae. Growers of Proteas, 

including Leucadendron, on a worldwide basis cooperate and exchange information via 

the International Protea Association (IPA) (Brits 1984; Criley 1998). 

II. BOTANY OF THE GENUS LEUCADENDRON 

114 

A. Taxonomy 

About 100 years passed between the discovery of South Africa and the beginning 

of scientific description of the proteas. In 1737, Linnaeus described the first two species 

of Leucadendron (L. argenteum and L. coniferum), but it took a long time to understand 

and to classify the South African proteas. With the introduction of the binomial system of 

nomenclature by Linnaeus in his Species Plantarum (1753), only six species of plants 

were listed under the name protea. In the case of L. argenteum, Linnaeus became lyrical 

in his description and stated that “This tree is the most shining and splendid of all plants,” 

but he then continued and wrote about the Silver Tree that: “yes, (it is) like Proteus 

himself extremely variable and different” (Williams 1972). The difficulties and 

misunderstanding were probably partly due to the fact that the genus Leucadendron is 

dioecious, and the male and the female plants are very different in appearance (Williams 

1972). A general introduction to the origin of the protea family can be found in Criley’s 

review on Leucospermum (Criley 1998), and the systematics and phylogeny of the 

African Proteaceae were reviewed recently by Rourke (1998). The taxonomy of the genus 

Leucadendron was revised about 30 years ago (Williams 1972). 

Recent studies, based on gene-sequencing data, have contributed to the 

understanding of the genetics, systematics, and phylogeny of the African Proteaceae, 

including Leucadendron (Barker et al. 1995; Hoot and Douglas 1998; Tansley and Brown 

2000). The genus Leucadendron is easily identified as having plants of separate sexes: the 

pistillate plants (known as female plants in the leucadendron literature) produce woody

conical, fruit-bearing flower heads, called “cones” (Rebelo 2001). The flower heads of the 

staminate plants (known as male plants in the leucadendron literature) do not form those 

conical flower heads. The conspicuous cones of the female plants consist of spirally 

arranged floral abracts, each of which covers a small flower (floret), and the bracts 

become hard and woody, forming the conical structures (Rebelo 2001). 

There are also morphological differences between the male and the female plants: 

the males are usually more branched and often slightly larger than the females, with 

smaller leaves and flower heads (Rebelo a2001). Bond and Midgley (1988) reported great 

differences in stem diameter, leaf area, number of inflorescences and mass of each 

individual inflorescence between the sexes of L. rubrum, and some differences in these 

characters in L. tinctum also. There are other extreme phenomena of dimorphism that 

distinguish between the sexes in L. rubrum (De Kock et al. 1994). 

Williams (1972) reviewed the taxonomic history of the main South African genera 

of Protea. Because emphasis had been placed on different features, the family had been 

divided into different genera in several different ways, and each genus into different 

groups of species. Williams a(1972) adopted R. Brown’s (1810) approach and based his 

classification of Leucadendron on division into sections and sub-sections, mainly 

according to fruit and floral characters (Table 4.1). Rebelo (2001) is continuing his 

research on the taxonomy and distribution of the genus Leucadendron, and much of the 

more recent information can be found in his Protea Atlas Project (Rebelo 2004). 

Thorough knowledge of the generic relationships among the Leucadendrons is 

contributing greatly to their horticulture and breeding. 

Rebelo (2001) simplified the use of Williams’ (1972) classification of the 

Leucadendrons by adding the English common name “conebush” to the genus 

Leucadendron as well as common names to the subsections (Table 4.1); he described 

each of the sections, subsections and species. Species belonging to the section 

Leucadendron have round nuts or nutlets (fruits) and those belonging to the section 

Alatosperma have flat, winged fruits. 

B. Distribution and Ecology 

The distribution range of the genus Leucadendron is limited to the Cape 

geological series in the southern Cape Province (Cape Floral Kingdom), with a small 

outlier on the Cape geological series near the coast in Natal (Williams 1972). All 

leucadendrons, except 3, are found in the Cape Floral Kingdom (Rebelo 2001) and all of 

them are well adapted to the fynbos vegetation type (Cowling and Richardson 1995). The 

fynbos is the most common vegetative type of the Cape Floral Kingdom, contributing 

more than 80% of its species, including the leucadendrons (Goldblatt and Manning 2000). 

Rourke (1980) defined fynbos as the sclerophyllous vegetation of the southwestern Cape, 

composed mainly of plants having fine, hard, heath-like leaves, or stems. The exact 

distribution of the individual Leucadendron species was described by Goldblatt and 

Manning (2000), and distribution maps were presented by Williams (1972) and Rebelo 

(2001). The survival risk for leucadendrons species in nature is: 2 extinct, 16 endangered, 

8 vulnerable, 17 naturally rare, and 1 uncertain (Hilton-Taylor 1996). Additional 

information is available at www.nbi.ac.za/protea. This situation is even more prevalent 

with regard to some of the local types and subspecies (Rebelo 2001). The South African 

Agricultural Research Council–Fynbos Unit has directed great efforts into the ex situ 

conservation of horticulturally important proteas, including leucadendrons (Littlejohn et 

al. 2000). 

115

Table 4.1. Classification of the genus Leucadendron (modified from Rebelo 2001). 

Subsection name 

Section Scientific Common z Species 

Leucadendron Villosa Sandveld brunioides, cinereum, 

concavum, coriaceum, 

dubium, galpinii, 

levisanus, linifolium, 

stellare, thymifolium 

Membranacea Arid arcuatum, bonum, remotum, 

pubescens 

Carinata Ridge-seed nitidum, sericeum 

Uniflora Pauciflor ericifolium, olens 

Aliena Kouga singulare, sorocephalodes 

Cuneata Fuse-bract corymbosum, laxum, 

verticillatum 

Nervosa Jonaskop Silver nervosum 

Leucadendron Silver album, argenteum, dregei, 

rubrum 

Nucifera Sun barkerae, burchellii, 

cordatum, cadens, 

daphnoides, glaberrinum, 

gydoense, loranthifolium, 

meyerianum, orientale, 

pubibracteolatum, rodii, 

sessile, sheilae, tinctum, 

tradouwense 

Ventricosa Crown chamelaea, elimense, 

globosum, grandiflorum 

Alatospermum Trigona Delta-seed conicum, floridum, 

loeriense, macowanii, 

pondoense, roukei, 

radiatum, salicifolium, 

uliginosum 

Brunneobracteata Oilbract microcephalum 

Alata Sunshine& Clay coniferum, cryptocephalum, 

diemontianum, discolor, 

eucalyptifolium, 

flexuosum, foedum, 

gandogeri, lanigerum, 

laureolum, meridianum, 

modestum, procerum, 

salignum, spissifolium, 

strobilinum, stelligerum, 

xanthoconus 

Compressa Needle-leaf comosum, immordoratum, 

muirii, nobile, osbornei, 

platyspermum, spirale, 

teretifolium 

z Cone bush 

The diversity, endemism, and distribution of leucadendrons and also of other 

Fynbos plants in the Cape Floristic Region are extensive. The rugged and dissected nature 

of the Cape landscape is a significant factor in the understanding of this diversity and 

endemism (Goldblatt and Manning 2000), as is the fact that after more than 250 years of 

116

Leucadendron research (Linnaeus 1753; Knight 1809) new species belonging to this 

genus are still being discovered (A. E. Van-Wyk 1990; Rourke 1997). Many studies and 

publications address various ecological and distribution aspects of the place of the 

Leucadendron species in the natural vegetation (Midgley 1998). Fires are an important 

factor in the life cycle of leucadendrons and affect the germination of its serotinous 

species, as well as some of the myrmecochorous and therophilous species (T. Rebelo, 

pers. commun. 2004). The fire causes the releases of the seeds from the cones to the 

ground, making the germination possible (Bond 1985; Le-Maitre 1988, 1989; Le-Maitre 

et al. 1992; Midgley 2000). Flower harvesting methods, seed dispersibility, and seed size 

affect the distribution and ecology of leucadendrons (Stock et al. 1990; Mustart and 

Cowling 1993a,b; Midgley 1998). The type of soil, its nutrient levels, its pH and hence its 

nutrient availability, as well as plant competition and tillage of the heathland soil are also 

important determinants of the distribution of Leucadendron in its natural habitat (Davis 

and Midgley 1990; Davis 1992; Mustart and Cowling 1993a,b; Mustart et al. 1994; 

Richards et al. 1997a,b; Laurie et al. 1997). 

Data regarding the climate of the Cape Region reveal average daily maximum 

temperatures of 28°C and 17°C in midsummer and midwinter, respectively. Extreme 

maxima reach 43°C in the summer and 30°C in the winter, and extreme minima reach 

4°C in midsummer and -5°C in midwinter. Temperatures, especially leaf temperatures, 

are greatly affected by ocean breezes and overcast skies. Annual rainfall ranges from 

3000 mm on some mountain peaks to less than 250 mm in some inland valleys (Schulze 

1984; Goldblatt and Manning 2000). The soils of the Cape region have various geological 

origins, including sandstone, granite, and limestone (Goldblatt and Manning 2000), and 

accordingly, in nature, different species of Leucadendron grow in sandy or heavy, boggy 

soils, and in soils with high or low pH (Williams 1972; Eliovson 1983; Laurie et al. 

1997). 

III. WORLD INDUSTRY AND ECONOMICS 

World trade in the three most widely used genera among the South African 

Proteaceae is estimated at 100 million stems annually, with the greatest volume involving 

a single Leucadendron cultivar ‘Safari Sunset’ (Littlejohn 2001). Littlejohn (2001) 

estimated the annual market volume of L. ‘Safari Sunset’ to be about 25 million stems; 

today, however, we know that the current volume is probably more than 40 million. A 

large proportion of the Leucadendron branches produced for the world market are of 

seed-propagated species and not of cutting-propagated cultivars (Table 4.2). This is 

especially true in the South African production of Leucadendron. Except for some 

hybrids, most of the seed propagated plants and those propagated vegetatively from 

unidentified clones are sold under the species name or under trade names. In many cases, 

the “old” synonymous species name is used as the trade/commercial name. In other cases, 

the species name is followed by an indication of whether the flower is male or female. 

The SAPPEX (South African Protea Producers and Exporters Association, undated) 

Catalogue includes 24 species and six cultivars of Leucadendron that are currently 

exported from South Africa. 

The main leucadendrons sold on the Sydney market are: L. ‘Silvan Red’, L. ‘Safari 

Sunset’, L. salignum red, L. salignum yellow, L. gandogeri green and yellow, L. 

laureolum green and yellow, L. ‘Tall Red’, L. ‘Inca Gold’ yellow, L. ‘Maui Sunset’, L. 

salicifolium, L. floridum ‘Pisa’, L. ‘Harvest’; leucadendrons with “cones” (“Christmasnuts” 

as it is called on the Sydney market in the mid-summer, Christmas season) include: 

L. galpinii and L. ‘Jubilee Crown’. More exotic Leucadendrons are: L. ‘Katies Blush’, L. 

‘Sundance’, L. tinctum, L. orientale, L. strobilinium, L. discolor female (white), L. 

discolor male (yellow with red center), L. argenteum, and L. elemense (with “nuts” at 

Christmas; Scott 2000). 

117

118 

A. Types of Leucadendron Cut Branches 

In analyzing the different types of Leucadendron cut products on the market, one 

may classify them into four main groups, more than one of which may be produced by a 

given species or cultivar during different seasons. The four main groups according to 

SAPPEX (undated) and L. J. Matthews (2002) include: (1) Foliage–cut branches are sold 

for their attractive foliage, which is relatively uniform along the whole length of the 

branch. The color of foliage varies among species and between specific clones: silver in 

silver tree (L. argenteum), green in ‘green discolor’ (L. discolor) and ‘Pisa’ (L. coniferum 

× �L. floridum), and light green in male L. platyspermum. The product is available almost 

throughout the year, except when new growth is too soft. (2) Attractive colorful “heads”– 

in these branches, when vegetative growth is stopped or slowed down and flowering 

commences, the larger terminal leaves become colorful. These involucre leaves 

commonly mistakenly known as “bracts” (Rebelo 2001, 2004) change their color during 

the marketing season. The main colors are various shades of red and yellow. Particular 

examples are: L. ‘Safari Sunset’, L. ‘Yaeli’, L. ‘Inca Gold’, and L. ‘Gold Strike’. 

Depending on the cultivar, the product may be available for long or short periods, though 

its shape and color may change in the course of the marketing season. (3) Male colorful 

“heads”–inflorescence and surrounding involucre leaves as in red and yellow discolors (L. 

discolor). The marketing season is extremely short (two to three weeks). (4) Branches 

terminating in attractive female cones–the main examples are females of: L. teretifolium, 

L. linifolium, L. galpinii, L. coniferum, L. salicifolium, L. platyspermum, and the cultivar 

‘Jubilee Crown’ (L. laureolum × �L. salignum). Some species or cultivars may be sold with 

attractive colorful involucral leaves and cones (e.g., L. ‘Safari Sunset’). This type of 

product has a long marketing period. 

Table 4.2. The main species and cultivars of Leucadendron in the international 

floricultural trade and their methods of propagation. (Sources: Cape Flora–South 

Africa, SAPPEX (Catalogue). 

Types of Plantation 

Seedlings 

Botanical 

Trade of cultivar 

name Clones 

All types 

of 

seedlings 

Special 

types 

Sex 

separated 

at harvest 

L. argenteum Silver tree x x 

L. coniferum Sabulosum x 

L. coniferum × 

floridum 

Pisa x 

L. discolor Green Discolor x x 

L. discolor Red Discolor x x 

L. discolor Yellow Discolor x x 

L. floridum Florida x x 

L. galpinii x 

L. laureolum Decorum Star x 

L. laureolum Laureolum male x 

L. laureolum × 

L. salignum 

Safari Sunset x 

L. linifolium Tortum female x 

L. linifolium Tortum male x 

L. laxum Smartrose x 

L. laxum Jubilee Crown x 

L. meridianum x

L. muirii x 

L. nervosum x 

L. nervosum Nervosum male x 

L. platyspermum Platy male x x 

L. platyspermum Platystar x x 

L. rubrum Rubrum female x x 

L. rubrum Rubrum male x x 

L. salicifolium Strictum x 

L. salignum Blush x 

L. salignum 

L. salignum × L. 

Red adscendens x 

eucalyptifoliu Chameleon x 

m 

L. teretifolium Cumosum x 

L. xanthoconus Salignum x 

L. laureolum × 

L. salignum 

Gold Strike x 

B. Yield 

It is difficult to assess the potential and the actual yields of leucadendrons. Yield 

may be counted in terms of production per plant or per hectare. In commercial plantations 

of L. ‘Silvan Red’, Barth et al. (1996) counted average annual yields of 314 and 219 

marketable stems per plant on highly fertile and infertile sites, respectively. They 

indicated that the plants were 1.0 to 1.5 m wide, but they did not indicate the distances 

between plants. However, in Australia, the planting density is generally 2600 plants per 

hectare (Cecil et al. 1995), so that the average annual yield is almost 700,000 stems per 

hectare. Leucadendron ‘Safari Sunset’ is planted in Israel at spacings of 2 m between 

rows and at 0.8 m within the row, i.e., 6250 plants per hectare (Shtaynmetz 1998; 

Shtaynmetz et al. 2004a). When planting is done in the spring, the average annual yields 

are 60,000, 150,000, 240,000, and about 400,000 marketable stems per hectare in the first, 

second, third, and fourth year onwards, respectively (Shtaynmetz et al. 2004a). The 

discrepancies between the Australian and Israeli figures may be related to the different 

cultivars and/or to the fact that in Israel the figure is solely for quality exportable stems. 

IV. HORTICULTURE 

A. Genetic Improvement 

In the early days of the protea industry, flowers were harvested from natural plant 

stands. Even now, many of the Leucadendron branches, especially those produced in 

South Africa, are harvested from natural fynbos or produced on seed-propagated species, 

rather than on cuttingpropagated, selectively bred cultivars. The first dedicated, scientific 

breeding of proteas–which included Leucadendron as an important component–was 

started in South Africa in 1973 (Brits 1983; Brits et al. 1983). The breeding of 

Leucadendron was initially based on the extensive collections that Marie Vogts had 

made, from nature, of so-called “commercial variants” (botanical ecotypes) of the best 

variations of species, and which she subsequently established in cultivation (Brits et al. 

1983). However, the trend towards production of high-quality cultivars of Leucadendron 

started in other countries, rather than South Africa (Littlejohn et al. 1995). Leucadendrons 

are easily reproduced by cuttings, therefore the improvement process has to produce only 

a single superior plant; the new cultivar can then be developed simply by multiplying this 

plant by means of cuttings. There are several ways to select the superior single plant from 

119

which to develop a new cultivar: taking cuttings from superior plants grown in the natural 

fynbos or in seedpropagated plantations, or developing superior variations by controlled 

or uncontrolled hybridization (Brits 1983). Hybrid seeds may be produced from crossing 

variants of the same species (intraspecific), or from crosses between species 

(interspecific). Hybrid plants may be produced by planting the parent plants in the same 

field and waiting for crosspollination to take place naturally (open pollination) and then 

collecting hybrid seeds, or by artificial, controlled pollination (van den Berg and Brits 

1995). In Leucadendron, the genetic variations available are vast and as yet largely 

untapped (Brits 1983; Littlejohn et al. 1995; van den Berg and Brits 1995). In 1995, 

Littlejohn et al. (1995) stated that the techniques to successfully hybridize any Proteas at 

will were not yet available, and that there was a need to overcome difficulties of low seed 

set and crossincompatibility between species. 

The natural pollination modes in Leucadendron differ among species; some 

species are wind pollinated and others depend on specific insects (Hattingh and Giliomee 

1989). In their review, Collins and Rebelo (1987) indicated that the pollination biology 

and breeding systems of Australian and southern African Proteaceae resemble one 

another. Proteas exhibit low seed set relative to the number of flowers available, and 

functional abandromonoecy (overcrowded, functional and non-functional flowers on the 

same receptacle) seems to be the main cause of poor seed set (Hattingh and Giliomee 

1989). 

Originally, leucadendrons were marketed mainly as green/foliage type flowers. 

Van den Berg and Brits (1995) were the first to recognize the potentially high market 

demand for superior quality Leucadendron single-stem cut flowers as a separate product. 

They pointed out that it was almost impossible to find all the desirable cut flower 

combinations of attractive large flower heads, long flowering branches and a high yield, 

within a single species, and argued that interspecific crosses must be used to combine the 

desirable qualities from different species. It was, however, much earlier, in the early 

1960s, that the first excellent, single stem cut flower cultivar ‘Safari Sunset’ was 

originated; it served as the role model for Brits’ and van den Berg’s 1986 research project 

(Bell 1988; Matthews and Carter 1983; van den Berg and Brits 1995; Matthews 2002). 

Heterosis (hybrid vigor) is often found in proteaceous hybrids (Brits 1983). In 1986 van 

den Berg and Brits (1995) started an extensive and systematic interspecies hybridization 

program with Leucadendron, intended partly to study both interspecific compatibility and 

heterosis in this genus. They found, surprisingly, a relatively high incidence of successful 

crosses, as well as high seed set, in the crosses, especially among the Alatosperma. 

Furthermore, among over 3000 hybrid seedlings produced from 36 interspecific crossing 

combinations, with average seed set approaching 50% of the pollinated florets, the 

majority showed strong hybrid vigor. This demonstrated the unusual potential for 

systematic interspecific breeding in Leucadendron. 

In The International Proteaceae Registrar (including the register and the 

checklist, Sadie 2002) are listed over 110 names of Leucadendron cultivars; of these 38 

are interspecific hybrids (Table 4.3, Sadie 2002). Most of the successful crosses are 

among species of the Section Alatosperma, Subsection Sunshine (Alata) con bushes, 

mainly between L. laureolum × �L. salignum. However, there are reported hybrids between 

species belonging to different Subsections (L. discolor × L. lanigerum) and even between 

species belonging to different Sections (L. elimense × �L. laureolum). The main species 

used for successful, interspecific hybridization are listed in Tables 4.3 and 4.4 (Sadie 

2002). The first four cultivars of Leucadendron were developed in New Zealand during 

the 1960s. Sadie’s Registrar lists eight cultivars developed in the 1970s, 42 during the 

1980s, and 51 during the 1990s. 

120

Table 4.3. Number of successful interspecific hybrid combinations as reported in “the International Protea Registrar” (Sadie 2002). 

Species/ 

eucalyptigrandolanilauresaligspissiuliginoxantho- Species discolor elimense foliumgerigerumolumnumfolium tinctum sumconus Total 

conicum 1 1 2 

coniferum 1 1 2 

daphnoides 1 1 1 3 

discolor 1 1 2 3 1 8 

elimense 1 1 

Eucalypti- 

2 2 4 

folium 

gandogeri 1 1 

lanigerum 1 1 2 

laureolum 14 14 

salignum 1 1

The first intentional breeding of Leucadendron was done in New Zealand, in the 

early 1960s. The original breeding was done by Jean Stevens of Wanganui and was 

continued by her son-in-law Ian Bell (Bell 1988; Matthews and Carter 1983; Matthews 

2002); they crossed Leucadendron laureolum with a red form of L. salignum, which was 

probably native to Langkloof, South Africa (FFTRI 1972; G. Brits, pers. commun., 2001). 

From this original cross emerged several selections, the best and most famous ones being 

L. ‘Safari Sunset’ and L. ‘Red Gem’. The registrar (Sadie 2002) lists 14 additional 

cultivars based on the same cross combination; the most famous of these is L. ‘Silvan 

Red’, which was bred in Australia in 1992 (Sadie 2002). 

It is difficult to select sufficiently superior cultivars just by selection within a 

species; therefore, crosses must be used to combine favorable qualities from different 

species. In the wild there are many “natural hybrids” between related species (for more 

information see www.nbi.ac.za/protea (protea information>protea ecology>hybrid 

relationships within proteas). It is more difficult to obtain viable crosses between 

taxonomically distant Leucadendron species (van den Berg and Brits 1995; Littlejohn 

2001; Robyn and Littlejohn 2001). Genetic and breeding research has been accelerated in 

the last 5 to 10 years, especially by the very active programs at the ARC in South Africa 

(van den Berg and Brits 1995; Littlejohn 2001; Robyn and Littlejohn 2001) and more 

recently in Western Australia (Sedgley et al. 2001; Yan et al. 2001; Croxford et al. 2003). 

Table 4.4. Classification of the main species used for interspecific hybridization in 

Leucadendron (Sadie 2002). 

Section Subsection Species 

Leucadendron Sun daphnoides, tinctum 

Crown elimense 

Alatosperma Delta-seeds conicum, uliginosum 

Clay lanigerum 

Sunshine coniferum, discolor, eucalyptifolium, 

gandogeri, laureolum, salignum, 

spissifolium, xanthoconus 

The current range of Leucadendron cultivars includes: (1) clonal selections from 

within species, such as L. salignum cultivars ‘Blush’ or ‘Yaeli’ (Ackerman et al. 1997a); 

(2) interspecific hybrids of speculative parentage, such as the L. laxum hybrid cultivar 

‘Jubilee Crown’; and (3) interspecific hybrids of known parentage such as the L. salignum 

× �L. eucalyptifolium cultivar ‘Chameleon’ or the L. laureolum × �L. elimense cultivar 

‘Rosette’ (Littlejohn et al. 1998; Littlejohn and Robyn 2000; Sadie 2002). 

Controlled pollination in Leucadendron is relatively simple, because of dioecy 

(Brits 1983). A. Robyn (pers. commun., 2000) recognized three main steps in achieving 

controlled hybridization among Leucadendrons: (1) covering the female inflorescence to 

prevent uncontrolled pollination– a cone of the selected female parent is covered for two 

to four days with a greaseproof bag to prevent wind or insect pollination while the 

stigmas ripen; (2) pollination–ripe pollen from the selected male parent is applied to the 

ripe stigmas of the female florets, with a fine brush, and the pollinated cones are again 

covered with the greaseproof bags; and (3) seed maturation–the seeds in the successfully 

pollinated florets must ripen to full maturity on the plant during the following four to six 

months, before harvesting. 

The following are the main aspects of a breeding program: (1) Pollen collection, 

storage, and viability assessment–since interspecific hybridization is a necessary approach 

to the development of superior new cultivars of Leucadendron (van den Berg and Brits 

1995), and since different species flower at different times of the year, it is important to 

develop methods for storing pollen. Both investigating teams, in South Africa and in 

122

Western Australia, studied pollen storage and assessment. Sedgley et al. (2001) 

recommended collecting male flower heads at anthesis: the cut stems, bearing many 

flower heads, are held at room temperature, and pollen can be separated from the 

flowering heads by removing the entire heads and sieving the pollen through a fine mesh 

sieve onto clean paper. The pollen is placed in open tubes within a sealed jar containing 

freshly dried silica gel at 4°C for 48 hr. The tubes should then be kept at either -20°C for 

short-term storage or at -80°C for long-term storage (Sedgley et al. 2001). Viability may 

be assessed by counting percentage pollen germination and pollen tube growth or by use 

of a fluorescent dye (Sedgley et al. 2001). (2) Hybridization compatibility–the main 

successful interspecific crosses in the genus Leucadendron are those between closely 

related species. Hybridization compatibility may be evaluated by scoring pollen-pistil 

interactions (Yan et al. 2001), or by estimating the percentage seed set (van den Berg and 

Brits 1995; Robyn and Littlejohn 2003). (3) Inheritance of important traits–relatively little 

is known about the genetics of Leucadendron and how important traits are inherited in 

these plants. Croxford et al. (2003) analyzed the inheritance of some important traits. (4) 

Survival at different trial sites–survival of hybrids was related to genotype, site, and the 

interaction between these two factors. Hybrid seedlings sometimes died because of 

incompatibility and delayed genetic incompatibility. The various sites had differing soil 

types and thus differed in the severity of infection from soil-borne pathogens, including 

Phytophthora cinnamomi. It has been observed that hybrids between pairs of parents 

chosen from L. strobilinum, L. loureolum. L. gandogeri, L. eucalyptifolium, L. 

xanthoconus, L. uliginosum, L. salicifolium, and L. muirii survived well in unfavorable 

sites, whereas when one of the above was crossed with L. procerum the tolerance of the 

resulting hybrids to those adverse sites was lost. (5) Juvenility–the length of the juvenile 

period was related to the parental combinations. Crosses having L. muirii, L. discolor L. 

procerum, L. salignum, L. spissifolium, L. strobilinum, or L. gandogeri as at least one 

parent produced hybrids with long juvenile periods, whereas crosses with species of the 

trigona subsection usually produced hybrids with shorter juvenile periods. (6) Flowering 

time–in general, the flowering time of hybrids is closely related to that of the parental 

species. Van den Berg and Brits (1995) found a wide variation of flowering times in their 

hybrid leucadendrons, ranging from June to September (Southern hemisphere). (7) Color 

of male flower heads–most male flower heads are yellow; however, two species, L. 

discolor and L. procerum can produce bright red male flower heads. When female plants 

from these species were crossed with other species, all the male offspring produced red 

flower heads. On the other hand, when a red L. discolor male was crossed with other 

species, only 70% of the male offspring were red. These results should be viewed as 

preliminary observations, indicating the beginning of understanding color inheritance in 

Leucadendron. (8) Bract (or more correctly “Involucre leaves”) color–most 

Leucadendron species have yellow or green bracts, but some genotypes of L. salignum 

have red bracts or combinations of these colors. Some species have their own unique 

bract colors. Crosses between red-bract L. salignum and yellow-bract species often 

produced hybrids with red bracts. When the red-bract hybrid ‘Red Gem’ (an F1 hybrid 

between red L. salignum and yellow L. laureolum) was crossed with L. laureolum (yellow 

bracts), 50% of the offspring had yellow bracts and 50% red ones, indicating a simple 

single- gene inheritance of the red color. Hybridization with the ‘Langkloof’ forms of L. 

salignum seems to offer special potential, since these plants effectively have two distinct 

flowering seasons: in winter-spring, when flowering proper occurs, and in midsummer at 

the termination of elongation growth, when the fully expanded terminal bracts (‘flower’) 

turn bright red (usually). This latter stage may be the most lucrative for marketing the 

plant–as in the case of ‘Safari Sunset’ (van den Berg and Brits 1995). (9) Plant form–the 

leucadendrons most suitable for use as cut flower varieties have an upright form and an 

annual vegetative flush of long, straight stems, which may be single-head or multi-head. 

It has been observed that, in some species, the flowering stems of female plants tend to be 

single-head and those of male plants multi-head. In general, hybrids tended to combine 

form traits from both parents. (10) Regeneration from epicormic buds of the lignotuber– 

123

the ability to regenerate new shoots from the base of the plant is an important quality for a 

good cut-flower cultivar. It seems that all the hybrids that result from a cross between a 

species with and one without a lignotuber have functional lignotubers, even though these 

may not be morphologically prominent (Brits et al. 1986). Second generation crosses of 

the above with a species with no epicormic trait produced hybrids that lacked this 

important trait. (11) Chromosome number–Croxford et al. (2003) counted the 

chromosomes of 25 genotypes from 15 different species and found that in all of them 2n 

= 26. These counts agree with the findings of de Vos (1943). 

Croxford et al. (2003) found neither aneuploidy nor euploidy in their counts. 

Littlejohn (1996c, 1997) evaluated Leucadendron selections according to the following 

traits: characteristics of the bush, the leaves, and the flower heads, flowering time, the 

ability to recover after harvesting of the flowers, and the yield. In many of these traits, she 

found great differences between closely related cultivars. For example, the average 

single-stem yields of various L. salignum clones ranged from eight per plant for the least 

productive to as high as 65 per plant for the most productive (at the third harvest). 

124 


Malan (1992, 1995) reviewed the various propagation methods used for proteas. 

Here we outline some of these methods and add some accounts of practical experience 

reported by commercial propagators in Israel. 

1. Seeds. 

Seeds are used for propagating Leucadendron for two reasons. Firstly, many of the 

Leucadendron branches sold on the world market are still harvested from seed-propagated 

species. This is especially true in South Africa, where most of the production is based on 

broadcasting seeds on ripped ground (M. Middelmann, pers. commun. 2002) and not on 

vegetatively propagated cultivars. The second reason is that propagating from seeds is 

part of the process of breeding new cultivars. In general, proteas do not set abundant 

seeds, especially when they are grown outside their natural habitat, out of reach of their 

unique pollinators. In Leucadendron, cross pollination is obligatory since they are 

dioecious plants and is accomplished by insects, mainly beetles, or/and by the wind. The 

10 most common wind-pollinated Proteas in southern Africa are all Leucadendron species 

(Rebelo 2001). Among southern African Proteaceae, the average percentage of florets that 

set seeds ranged from 77% in Leucadendron and 100% Aulax, to 8% in Protea and 15% 

in Leucospermum (Rebelo and Rourke 1986). 

Leucadendrons have two major types of seeds (strictly speaking, achenes): nutlike 

(6 being myrmecochorous–ant dispersed, and over 25 species are rodent dispersed) 

and serotinous (Bond 1985; Brits 1986b; Rebelo 2001). This biological dichotomy is 

common among the seeds of SA Proteaceae at the generic level with Aulax and Protea 

serotinous and the remaining genera being myrmecochorous. Rodent-dispersed seeds are 

only known in Leucadendron. The unique feature of Leucadendron to contain more than 

one seed type prompted Salisbury (in Knight 1809) to split the genus into several genera 

based on seed morphology–his groupings are now recognized at the subgeneric level. 

These seeds are rounded, nut or nutlet-like, and are relatively hard-shelled (Williams 

1972; Brits 1986b). Myrmecochorous nutlets are covered with a fleshy skin–called the 

elaiosome–that attracts ants, which carry them away and store them in their nests. 

Serotinous seeds have a flattened, winged shape and are retained on the plant for long 

periods, in live (turgid) protective woody cones or seedheads that protect them from fire 

and predators. They are released and dispersed by a hygroscopic mechanism that is 

activated by dessication when the water supply to the seedheads stops as a result of fire or 

the death of the plant (Brits 1987; Rebelo 2001). 

The seeds are ripe for harvesting 6-7 months after flowering, when the young 

flower heads on the tips of the new growth are already developing (Vogts et al. 1976). 

Serotinous seeds are common in species of the Section Alatosperma (Table 4.1).

With regard to dormancy and germinability, it is important to distinguish between 

two main types of seeds: the hard-coat nuts and the flat seeds (Brits 1986b). The first type 

is more difficult to germinate and should be handled similarly to other hard-coated 

proteaceous seeds; it includes Leucospermum (Van Staden and Brown 1977; Brits 

1986b,c). Dormancy of hard-coated seeds can be overcome by mechanical or acid 

scarification, by hydrogen peroxide treatment (Brits 1986a,b; McLennan 1993; Brits et al. 

1995), or by soaking the seeds in hot water (Harre 1988), although the last method may 

be an indirect form of scarification, which occurs when desiccated seeds are wetted (Brits 

et al. 1993). 

Rourke (1994) stated that John Herschel studied the effect of heat on germination 

of Leucadendron argenteum as early as 1836. Herschel wrote: “The seeds of protea 

argentea will be several years in the ground without germinating–but if the seeds be sown 

half an inch deep and then the ground burnt they come up at once.” This reaction may in 

fact be induced indirectly by the desiccating effect of heat on the buried seeds, followed 

by watering (Brits et al. 1993): treating any well-desiccated fynbos nut-fruited Proteaceae 

seeds with free water may result in cracking of the seed coat, which amounts to 

mechanical scarification, and subsequent dormancy breaking, i.e., germination. However, 

scarification may also mechanically assist the embryo to emerge, which is probably a 

much lesser effect than that of oxygenation (van Staden and Brown 1977). 

Van Staden and Brown (1973) and Brown and van Staden (1973b) in studies of 

the effects of oxygen on endogenous cytokinins levels and on germination of 

Leucadendron daphnoides, which has hard-coated seeds, found that scarification 

treatments and incubation of seeds in oxygen improved germination under alternating 

temperatures. The effect of high oxygen appears to be mediated by increased levels of 

endogenous cytokinins, since the latter condition is closely correlated with enhanced 

germination. Brits (1986b) showed that soaking in 1% H2O2 solution for 24 hr could be a 

practical way of oxygenating non-scarified, hard-coated proteaceous seeds. In 

Leucadendron, flat or winged seeds (alatosperma) appear not to need additional 

(artificial) oxygenation. The stimulating effect of elevated oxygen partial pressure within 

intact hard-coated seeds is consistent with the stimulating effect of scarification, which 

acts by breaking the impermeability of the intact seed coat to atmospheric oxygen, so that 

seeds are subsequently naturally oxygenated from the air (Brits et al. 1993). The effect of 

daily alternating temperature on germination of the hard, nut-like seeds of Cape Proteas 

has been studied thoroughly by Brits (1986c). It appears that all nut-like proteaceous 

seeds, including Leucadendron, require daily temperature variations between about 8°C- 

10°C night (16 hr) and 20°C day (8 hr) for optimal germination. There are also 

indications that some aqueous germination inhibitors may be present in seeds of L. 

daphnoides (Brown and van Staden 1971). There are many publications on dormancy and 

germination in proteas (Brown 1975; Brown and van Staden 1973a,b,c; van Staden and 

Brown 1977; Brown and Dix 1985), and recently Criley (1988) summarized all the 

methods being used for overcoming seed dormancy in hard-coated proteaceous seeds. In 

summary, all high quality Leucadendron seeds primarily need low temperature, 

preferably 10°C, with daily fluctuations to 20°C for successful germination; and nonscarified 

(intact) hard-coated seeds also need oxygenation (Brits 1986b; Brits et al. 1993). 

After overcoming dormancy, the main cause for failure in propagating 

leucadendrons by seeds is death caused by fungi, and these deaths can occur both pre- and 

post-emergence. The development of damping off diseases is always accelerated by the 

presence of high levels of inocula in the germinating medium, and by excessive watering, 

insufficient aeration, and excessively high temperature (Harre 1988). Recently, Brown 

and Botha (2002) reported that seeds of L. rubrum and L. tinctum increased germination 

in response to smoke. The germination percentage also depends a great deal on the source 

of the seed and the species, i.e., on seed quality (Robyn and Littlejohn 2001). 

There are several ways to sow the seeds: (1) broadcasting, is used mainly in South 

Africa. The mature cones are shredded and, without separating seeds from other 

components, the shredded material is broadcast onto ripped fields; (2) inserting brunches 

125

with the matured cones in the ground. This is done with L. platyspermum, whose winged 

seeds may germinate before they emerge from the cones (Rourke 1998); (3) sowing in 

open beds; (4) sowing in shallow flats, which can be placed in the open or in a shade 

house and irrigated when necessary, or irrigated once and then stacked for 17-26 days at 

controlled temperatures (see recommended temperature regime above). When 

germination begins, the flats are removed from the stack and placed in an exposed 

location. Temperature fluctuations between 10°C (night) and 20°C (day) are essential for 

optimal germination (Brits 1986c); (5) seeds are spread between two layers of canvas and 

placed under mist in an unheated shade house, in autumn or mild winter. Seeds that are 

starting to germinate are collected every few days and placed in small pots; and (6) seeds 

are sown in individual plugs and a few days after germination the plugs with the 

germinated seeds are moved to a different location with a suitable irrigation regime. 

Publications that address the seed ecology of Proteaceae include Bond (1988), 

Bond et al. (1995), and Bond and Maze (1999). Publications concerning seed germination 

under natural conditions were written by Brits (1987), Mustart and Cowling (1991), 

Lamont and Milberg (1997), and Musil et al. (1998). 

2. Cuttings. 

Most cultivars of Leucadendron are no longer considered difficult to root by 

means of standard techniques (Malan 1995). Jacobs (1981) indicated that the fall (March, 

April in the Southern hemisphere) is the best time for rooting leucadendrons. Nurserymen 

in Israel and New Zealand (Harre 1988) root leucadendrons all year round, provided that 

suitable wood is available and that there are proper facilities for rooting the cuttings. 

Terminal and sub-terminal cuttings can be used, which should not be “too soft” nor “too 

hard”; if too soft they will rot in the propagation bed, and if too hard they will root only 

after several months or not at all. It is best to use wood not more than 6 months old (R. 

Arlevsky, pers. commun. 2002). The cuttings, measuring 12 cm long by 8 mm diameter, 

should be taken from good healthy plants, grown under full sunlight, washed well, 

disinfected, e.g., with active chlorine solution, and kept under refrigeration until being 

inserted in the propagation bench. 

Cuttings should be treated with rooting hormones; Malan (1995) gave a general 

recommendation of 4000 ppm IBA for proteas. Harre (1988) indicated an optimal level of 

2000 ppm for Leucadendron, and recommended reducing this concentration to 1000 ppm 

for ‘hairy-leaf’ varieties. A 1-cm length at the base of the cuttings should be placed in the 

hormone solution for 10 seconds. The cuttings should be inserted in well drained and 

sterilized growth medium. Malan (1995) recommended sand: peat: polystyrene (1:1:1 

v/v/v). In Israel it is common to use a mixture of finely ground polystyrene: medium-size 

peat (7:3 v/v) packed in “Ellepot” propagating plugs (Ellegard, Denmark). 

The cuttings should be kept under a mist system in a protected and well-aerated 

greenhouse, with a light intensity of about 300 lux. Under Israeli conditions, in the 

summer the plastic cover of the propagation house is whitewashed and a 30% shade net is 

placed inside the house; in winter the whitewash is washed off by the rain and the 30% 

net is kept in position. In New Zealand, Harre (1988) recommended allowing full light 

intensity during the morning and evening, and cutting the 900-lux full light intensity at 

midday by 50%; higher light intensity could be maintained if it is possible to do so 

without elevating the temperature. The temperature at the base of the cuttings should be 

kept at a minimum of 18°C, and the air temperature should not exceed 26°C. The pad and 

fan cooling system is recommended. However, the high-humidity/high-temperature 

environment is excellent for the spread of diseases, against which a high level of 

phytosanitary conditions should be maintained. The house should be well aerated and the 

plants should be sprayed regularly against foliar diseases. To prevent root rots, the 

medium should be drained against Pythium and similar diseases with materials such as 

Dynon (propamocarb) or Rizolex (tolclofos-methyl). When all the recommendations are 

followed, good propagators achieve 85-95% well-rooted plants. 

There have been several detailed studies that provide some additional information 

126

on propagation by cuttings of leucadendrons: Rodriguez-Perez (1992) examined the 

possibility of using leaf-bud cuttings of L. ‘Safari Sunset’, and achieved a maximum 

rooting of 20%. The use of leafbud cuttings may be advantageous when the quantity of 

propagating wood is limited, but the low rate of rooting makes this method impracticable. 

Rodriguez-Perez et al. (1993) showed that wounding the base of the cuttings significantly 

improved the rooting percentage of L. ‘Safari Sunset’. Perez-Frances et al. (2001a) 

studied the anatomy of adventitious root formation on wounded and unwounded cuttings 

of L. ‘Safari Sunset’ and L. discolor, and were able to show that adventitious root 

formation was initiated mainly in the wounded area, and at the basal cut surface of the 

cuttings. They also found that root primordia were present in the wounded areas as soon 

as 2 weeks from the time of inserting the cuttings. Perez-Frances et al. (2001a) cited 

MacKenzie et al. (1986) as claiming that wounding the bases of cuttings improved their 

rooting. Epstein et al. (1993) studied the metabolism of IBA in two cultivars of L. 

discolor–one early flowering and the other late flowering. He demonstrated that the early 

flowering rooted well, whereas the late flowering was difficult to root; ‘early’ also 

responded better to a 4000- ppm IBA treatment. Five weeks after inserting the cuttings, 

the rooting results were as follows: untreated ‘early’, 17%; hormone-treated ‘early’, 77%; 

untreated ‘late’, 0%; and hormone-treated ‘late’, 10%. Epstein et al. (1993) showed that 

these differences in rootability were related to IBA transport and metabolism in the 

cuttings. There were higher levels of IBA accumulation at the base of the ‘early’ rooting 

cultivar than in the ‘late’, difficult-to-root one. 

Ben-Jaacov et al. (1995) studied the rooting of L. linifolium cuttings, produced 

outdoors in vitro conditions, found that NAA, CO2 enrichment, and sucrose all affected 

rooting. NAA had the greatest effect among the factors tested, but photosynthesis and 

sugar levels were also important. When the cuttings were treated with NAA, without 

adding either CO2 or sucrose, rooting was only 25%. When the atmosphere in the test 

tubes was enriched with CO2, rooting was increased to 41%, probably because of 

enhanced photosynthesis. When sugar was included in the medium, without CO2 

enrichment, rooting was at a similar level of 43%. However, it is most interesting to note 

that when both sucrose and CO2 were used, rooting was increased to 70%. These results 

may have some important implications, both for rooting of cuttings and for propagation of 

Leucadendron in tissue culture. 

3. Grafting. 

The aim of plant breeding is to make genetic improvements, especially those that 

lead to better quality and higher yield. It is, however, a long and expensive process. To 

make breeding more efficient, it is possible to breed the scion and the rootstock 

separately. Grafting is a common technique that is practiced in fruit trees, ornamentals, 

and vegetables (Gardner 1958; Elliot and Jones 1982; Hartmann et al. 1990; Lee and Oda 

2003), and its use had already been suggested in the early days of protea cultivation 

(Rousseau 1966; Anonymous 1971; Vogts et al. 1976). Many of the Australian 

proteaceous plants are often grafted (Elliot and Jones 1982; Barth and Benell 1986; 

Crossen 1991). A comprehensive study of grafting of Leucospermum was carried out 

from 1976 to 1980 by Brits (1979; 1990a,b). Moffatt and Turnbull (1994) carried out a 

wide ranging study on grafting, which covered many Protea, Leucospermum, and 

Leucadendron species, and presented the following reasons for grafting proteas: to 

overcome soil-borne diseases, especially phytophthora and nematodes; to enhance soil 

adaptability; to propagate hard-toroot clones; to achieve rapid increase of genetic stock; 

and to preserve endangered selections. However, their studies, and those of Brits, were 

mainly intended to enable the cultivation of proteas in phytophthorainfested areas of 

Eastern Australia (Turnbull 1991; Moffatt and Turnbull 1994) and South Africa (Brits 

1990a, 1990b). At about the same time, Ben-Jaacov et al. (1989a, 1991a, 1991b) and 

Ackerman et al. (1997b) demonstrated the beneficial effect of using L. ‘Orot’ (a local 

selection of L. coniferum) rootstock on the growth of L. ‘Safari Sunset’ and L. discolor in 

extremely high pH soils in Israel. This demonstration and publications in the local trade 

127

journals stimulated local nurseries to produce commercial quantities of grafted 

Leucadendron plants that were planted in all parts of the country, in all types of soils, and 

in artificial growth media (Ben-Jaacov et al. 1991b; Ackerman et al. 1997b). 

Grafting efficiency was greatly improved with the development of the “cuttinggraft” 

method (Burke 1989; Gibian and Gibian 1989; Ackerman et al. 1997b). This 

simultaneous rooting-grafting method, designated as “stenting” by Van de Pol et al. 

(1986), is frequently used for propagating roses. Most of the commercial Leucadendron 

grafting in Israel is done by “cutting-grafts”. Wedge-grafting is used and tying is done 

with Parafilm strips (Ackerman et al. 1997b). The nurseryman R. Arlevsky (pers. 

commun., 2002), recognized that L. galpinii might serve as a good rootstock for 

Leucadendron. Field observations of L. ‘Safari Sunset’ plants grafted on L. galpinii and 

on L. ‘Orot’ showed differing behavior of these rootstocks in different soils. It is well 

known that different species of Leucadendron have differing degrees of adaptability to 

different soil conditions (Eliovson 1983); also, different cultivars respond differently to 

differing phosphorus regimes (Silber et al. 2000b). Recent studies of water requirements 

of grafted and non-grafted L. ‘Safari Sunset’ indicated that there were interactions 

between the rootstock and the water requirements: grafted L. ‘Safari Sunset’ on L. ‘Orot’ 

produced higher yields of flowers under lower levels of irrigation than L. ‘Safari Sunset’ 

on its own roots. On the other hand, the grafted plants were more sensitive to soil-borne 

diseases under a high-watering regime (Silber et al. 2003). All the information reported 

above suggests that further studies are needed of the suitability of rootstocks to specific 

cultivars, specific soils, and specific cultivation technologies. 

Grafting compatibility has never been studied methodically: Van der Merwe 

(1985) tried to understand the intergeneric relationships among the Proteaceae by 

comparing grafting compatibility between the genera. In general, it seems that grafting 

compatibility between species in Leucadendron is wider than their hybridization 

compatibility (Ben-Jaacov et al. 1991b; Moffatt and Turnbull 1994; R. Arlevsky, pers. 

commun., 2002). Table 4.5 (modified from Moffatt and Turnbull 1994) summarizes 

leucadendrons grafting. The rootstocks used all belonged to the section Alatosperma. Of 

the scions used, six were species belonging to the section Leucadendron, and nine to 

Alatosperma. When the first group (Leucadendron on Alatosperma) was used, 37% of the 

grafting combinations were 100% successful and 37% gave a success rate below 50%. 

When the second group (Alatosperma on Alatosperma) was used, 32% of the grafting 

combinations were 100% successful and 12% gave a success rate below 50%. The 

conclusion from these data is that there was no correlation in grafting compatibility within 

the sections or between the sections. The same conclusion may be drawn, regarding 

grafting compatibility between or within the sub-sections. Two species predominate as 

rootstocks in Israel: L. galpinii and L. ‘Orot’ (a local selection of L. coniferum). 

Successful (i.e., the plants stayed alive for at least 5 years) grafting of the following 

species and cultivars on these rootstocks has been achieved: L. discolor, L. ‘Safari 

Sunset’, L. ‘Yaeli’, and L. argenteum (R. Arlevsky, pers. commun., 2002). 


Success rates (in vitro multiplication) varied greatly among members of the 

Proteaceae (Perez-Frances et al. 2001b). Research on in vitro propagation has been done 

with most of the commercially grown proteas (Ben-Jaacov and Jacobs 1986), but at 

present, commercially grown cultures are available only of some Grevilleas, and a few 

cultivars of Telopea. Since Leucadendron can be easily propagated by cuttings, there has 

been little effort to propagate them in vitro. Perez-Frances et al. (2001b) reported 

successful establishment of L. discolor in vitro; they used spring-grown nodal and shoottip 

explants, and treated them with polyvinyl-pyrrolidone to prevent oxidation. Shoots 

grew and proliferated on half-strength MS medium containing 3% sucrose, 0.7% agar, 

and benzyl adenine at 0.5 mg L -1 . The multiplication rate was low, and it declined with 

sub-culturing. Earlier attempts to propagate L. ‘Safari Sunset’ in vitro failed because of 

the very low multiplication rate (Perez-Frances et al. 1995). Recently, Ferreira et al. 

128

(2003) reported an efficient method for in vitro propagation of L. ‘Safari Sunset’: a 

modified MS medium containing ascorbic acid (15 mg L -1 ) and 2% sucrose, amended 

with BAP at 2 mg L -1 and GA3 at 2 mg L -1 , and obtained seven 19-mm-long shoots from 

each explant. They cut off these shoots, dipped their basal ends in auxin solution (IBA 1 g 

L -1 ) for 5 min and for rooting placed them on solid medium or Sorbarods plugs saturated 

with basal liquid medium, without growth regulators. In both cases, 83% of the shoots 

showed root formation. The small rooted plantlets exhibited cytological and 

morphological modifications that might be responsible for their incapacity to survive ex 

vitro. 

C. Site Selection and Environmental Responses 

Leucadendrons and other Proteas are commercially cultivated, very successfully in 

many places, under very different environmental conditions from those found in their 

natural habitats (Veld and Flora 1984). Ben-Jaacov (1986) used revised versions of the 

Climatic Diagrams of Walter and Helmut (1976) to illustrate the climates of the main 

protea production areas around the world. All books about Proteas emphasize the 

importance of proper site selection for their cultivation, including that of leucadendrons. 

Most of these recommendations, however, are based on the various authors’ experience 

and the environments and soils found in their own areas, and are therefore not always 

relevant to other places. Matthews (2002) describes 32 species and cultivars of 

Leucadendron, 28 of which are suitable for use as cut flowers or/and cut foliage. He 

discussed the hardiness of each, and indicated that most of them are hardy and sustain 

midwinter frosts of -3°C to -6°C. The plants can probably sustain these temperatures, but 

flowers of at least some of these species and cultivars (e.g., L. discolor) can be damaged 

even in lighter frosts. Eliovson (1983) indicated that L. album, L. arcuatum, and L. 

rubrum grow above the snowline or at high altitudes in the Cape mountains, and should 

tolerate cold conditions. 

Leucadendrons are evergreen, but the degree of their activity depends on the 

location of their cultivation. Vegetative growth of L. ‘Silvan Red’ in South Australia 

commenced between October and November (spring) and ceased by March (fall). During 

the summer peak growth season, the average elongation was about 12 cm per month and 

the average increase in diameter was 0.63 mm (Barth et al. 1996). At high elevation in 

Ecuador (0 degrees latitude), growth and flowering of L. ‘Safari Sunset’ continues year 

round (S. Pollack, pers. commun. 2004). 

129

Table 4.5. Grafting compatibility among leucadendrons belonging to various subsections (Source: Moffatt and Turnbull 1994). 

Delta-seeds CB 

(Alatosperma) 

Sunshine CB (Alatosperma) 

Safari 

Scion/Rootstock floridum macowanii eucalyptifolium gandogeri Sunset salicifolium xanthoconus 

Leucadendron 

galpinii (Sandveld) z - - 66 (26) 33 (28) - 100 (27) - 

arcuatum (Arid) 33 (20) y - 100 (26) - - 100 (20) - 

nervosum (Jonaskop silver) - - 100 (8) - - - - 

album (Silver) 0 - 100 (13) - - 90 (8) 57 (7) 

orientale (Sun) 16 (10) 50 (27) 0 - 100 (47) 57 (18) 

elimense (Crown) - - 28 (12) - - 100 (27) 16 (5) 

Alatosperma 

floridum (Delta-Seed) -- 100 (15) - - 100 (28) - 

macowanii (Delta-Seed) - - - 33 (28) - - - 

uliginosum (Delta-Seed) - 83 (27) 66 (30) - - 37 (17) - 

stelligerum (Clay) - - 0 - - - - 

discolor (Sunshine) - 100 (27) 83 (27) - - 66 (33) 77 (29) 

gandogeri (Sunshine) - - 77 (26) - - 100 (27) 71 (19) 

laureolum (Sunshine) - - 83 (14) - - 90 (27) 83 (12) 

procerum (Sunshine) - - 100 (29) - 91 (41) 66 (27) 100 (29) 

‘Safari Sunset’ (Sunshine) - 100 (27) 66 (21) - - 100 (33) 66 (15) 

z 

Cone bush 

y 

Successful grafts (%), in brackets: age of oldest grafts (months).

D. Cultural Practices 

1. Specific Requirements of Species and Cultivars. 

Methods of cultivation vary among species planted as seedlings and vegetatively 

propagated plants as well as among the cultivars themselves, and specialized publications 

supply information on the cultivation and post-harvest treatment of specific cultivars, e.g., 

L. ‘Rosette’, L. ‘Chameleon’, L. ‘Flash’, and L. ‘Asteroid’ (Littlejohn 1994a, 1994b, 

1996a, 1996b). In Israel, most of the publications intended to inform farmers are specific 

for L. ‘Safari Sunset’, the main protea produced in Israel (Shtaynmetz 1998; Shtaynmetz 

et al. 2002, 2004a), but there are also publications that deal specifically with other 

cultivars (Shtaynmetz et al. 2000). 

2. Spacing. 

Distances between plants and between rows vary according to the cultivar, 

methods of production, and traditions around the world: Barth et al. (1996), reporting the 

yield of fully producing, 6-year-old L. ‘Silvan Red’, indicated that the bushes were 1.0- 

1.5 m wide and 1.5-2.0 m tall; Cecil et al. (1995) indicated that in Australia, the planting 

density is generally 2600 plants per hectare. In Israel, L. ‘Safari Sunset’ is planted with 

spacings of 2 m between rows and 0.8 m within rows, i.e., 6250 plants per hectare, and 

some growers plant even more densely (Shtaynmetz et al. 2004a). It is recommended to 

leave a wider space between rows every 50 m, to allow the passage of harvesting vehicles 

(Shtaynmetz et al. 2004a). With smaller cultivars, such as L. ‘Yaeli’, the distance between 

rows can be reduced to 1.8 m (Shtaynmetz 1998; Shtaynmetz et al. 2000). 

3. Nutrition of Leucadendron. 

The Effect of P Application. Proteaceae originated in Australia and South Africa, where 

most species grow on leached soils, which are poor in available minerals (Handreck 1997; 

Richards et al. 1997a). Purnell (1960) described proteoid roots as “clusters of rootlets of 

limited growth which form lateral root”, are widespread in the Proteaceae. Similar root 

structures have been described in several other families, and Lamont (1982) described 

them as “root clusters”. Dinkelaker and Marschner (1995) divided the root clusters into: 

(1) proteoid-like root clusters, including (1a) proteoid roots of the Proteaceae, and (1b) 

other non-root clusters of the genera: Casaurina, Acacia, Lupinus, Kennedia, Viminaria, 

Myrica, and Ficus; and (2) non-proteoid-like root clusters, including dauciform, 

capilarroid, and stalagmiform roots of the Cyperaceae and Restionaceae, and of the genus 

Eucalyptus. The function of proteoid roots has been investigated since the early 1960s, 

but their specific role in uptake of nutritional elements, especially phosphorus P, was 

poorly understood. Jeffrey (1967) observed that the proteoid roots of Banksia ornata were 

very efficient in adsorbing P, and related this beneficial property to their high surface area 

rather than to a metabolic factor. Lamont (1983) and Lamont et al. (1984) too attributed 

the higher P uptake of proteoid roots to the greater soil volume they exploited, and found 

that, compared with non-proteoid roots, proteoid roots in Leucadendron laureolum had a 

15x �greater specific surface area (mm2 mg -1 ) and exploited a 33x �greater specific soil 

volume (mm3 mg -1 ). Jeffrey (1967) suggested that low P status in a plant induces the 

formation of proteoid roots and Lamont (1972) extended this idea to include deficiency 

levels of other nutrients, especially N. Several investigations demonstrated that a proper 

nutrient regime induced decreased formation of proteoid roots, and at the same time 

improved shoot growth (Lamont 1972; Groves and Keraitis 1976; Thomas 1981). 

Idealized relationships between soil nutrient availability and proteoid roots, non-proteoid 

roots, and shoot production are presented in Fig. 4.1. However, despite the clear 

evidences that adequate nutrition may be beneficial to shoot growth even in the absence 

of proteoid roots, Lamont (1986) stated that “There can be no denying that the presence 

of abundant proteoid roots is a sign of a healthy plant”. 

131

Fig. 4.1. Idealized relationships between nutrients availability and production of root 

clusters, other roots and shoots (copied from Lamont 2003, adapted from Lamont 

1982). 

Nutritional problems gave the impression of being the greatest single cause of 

difficulties in the nursery culture of proteaceous plants (Thomas 1974). During the 1970s 

and the 1980s, studies conducted in Australia, Hawaii, New Zealand, and South Africa 

focused on the nutritional demands of pot-grown Proteaceae (Specht and Groves 1966; 

Thomas 1974; Groves and Keraitis 1976; Nichols et al. 1979; Thomas 1980, 1981; 

Nichols and Beardsell 1981a,b; Goodwin 1983; Dennis 1985; Dennis and Prasad 1986; 

Claassens 1986; Heinsohn and Pammenter 1986; Parvin 1986; Prasad and Dennis 1986; 

Grose 1989; Buining and Cresswell 1993). It was found that P application to pot-grown 

plants induced growth impairment, leaf chlorosis and necrosis, and abscission of mature 

leaves (Thomas 1974; Groves and Keraitis 1976; Nichols et al. 1979; Thomas 1980, 

1981; Nichols and Beardsell 1981a,b; Goodwin 1983), therefore, P levels that generally 

applied for agricultural crops were regarded as toxic for the Proteaceae (Grose 1989). The 

problem introduced by Nichols et al. (1979), of why P levels that are essential for most 

other plants are toxic to the Proteaceae, remained unsolved. 

Elucidation of the problem posed by Nichols et al. (1979), regarding the effect of 

P nutrition on the development of Proteaceae, gained a breakthrough as a result of the 

excellent research conducted by Gardner on the legume white lupin (Lupinus albus L.). 

Gardner et al. (1982a,b, 1983) demonstrated that the availability of P and metal ions in 

the root environment of white lupin was improved as a result of excretion of citrate and 

protons from the proteoid roots. Furthermore, the activity of proteoid roots was primarily 

influenced by the P status in the plant, and their formation was depressed at high 

rhizosphere-P levels. High P levels and low proteoid root activity in turn reduced 

manganese uptake (Gardner et al. 1982b). Subsequently, numerous investigations using 

Lupinus albus as a plant model established a comprehensive knowledge on the 

interactions between P status in the plant and the formation and functions of proteoid 

roots (Dinkelaker et al. 1989; Dinkelaker and Marschner 1992; Gerke et al. 1994; 

Dinkelaker and Marschner 1995; Johnson et al. 1994, 1996a,b; Keerthisinghe et al. 1998; 

Watt and Evans 1999; Neumann et al. 2000). 

Recent and up-to-date reviews on these topics have been collected by Lambers 

and Poot (2003). It is generally accepted that the primary role of proteoid roots is 

associated with modification of the root environment, i.e., by exudation of organic acids 

132

(mainly citric) that enhance P mobilization towards the plant root. It seems that under 

intensive cultivation conditions, when all nutrient elements are supplied according to 

plant needs, the specific role of the proteoid roots is limited. 

In light of the recently accumulated knowledge, it is suggested that high rates of P 

application to proteaceous plants could reduce the availability of micronutrients, 

especially Fe, Mn, and Zn, because of: (1) precipitation of metal-P compounds; (2) 

enhancement of specific adsorption of metal ions on the charged surfaces of oxides and 

hydroxides in the soil following increases in negative charges; and (3) a decrease in 

solubilization of metal ions following the decrease in excretion of organic acids. It is 

possible, therefore, that the symptoms of growth impairment, leaf chlorosis, necrosis, and 

abscission of mature leaves that characteristically affect proteaceous plants following P 

application, and which in the past were attributed to P toxicity, actually derive from 

deficiency of metal ions. Thus, it may be correct to extend the term “P-induced zinc 

deficiency” introduced by Cakmak and Marschner (1986, 1987), to Fe, Mn, and/or any 

other metal micro-nutrient. This suggestion is supported by Handreck’s (1991) 

observations that iron deficiency was the main visible effect of P excess on the shoot of 

Banksia ericifolia, that its severity increased as the P supply increased, and that classic 

symptoms of P toxicity appeared in plants exposed to high levels of P and low Fe 

supplementation. 

Nutritional Demand of Leucadendron. The nutritional demands of Leucadendron ‘Safari 

Sunset’, the most important cultivar in the protea industry, have been extensively 

investigated during the last two decades (Silber et al. 1998, 2000a,b,c, 2003). The 

objective of the research was to assess the response of L. ‘Safari Sunset’ to nutritional 

management, especially that of phosphate, and all their findings showed that adding 

fertilizer to the irrigation water resulted in increased biomass production compared with 

that of tap-water-irrigated plants. The nutritional treatments affected the development of 

proteoid roots, and root clusters were present mostly in tap-water-irrigated plants. Some 

proteoid roots developed on plants irrigated with nutrient solution when P was omitted, 

but none developed in any of the other treatments. Increasing the P concentration up to 20 

mg L -1 significantly improved L. ‘Safari Sunset’ growth and there was no indication of 

toxic symptoms that could be attributed to an excess of P. These results are consistent 

with the conclusions of Prasad and Dennis (1986) that realistic levels of soil-P 

concentration (below 40 mg kg -1 as assessed by bicarbonate extraction) are not toxic to L. 

‘Safari Sunset’. 

A significant quadratic regression was obtained between the number of marketable 

branches and leaf-P concentration of L. ‘Safari Sunset’ plants exposed to various nutrient 

application rates (Silber et al. 2000a), and similar relationships were obtained for the fresh 

and dry weights of shoots (not presented). According to the quadratic equation presented 

in Fig. 4.2, the maximum number of marketable branches was achieved when leaf-P 

concentration approached 3.4 g kg -1 DW, similar to what has been reported for many 

plants (Marschner 1995). These results indicate that L. ‘Safari Sunset’ plants are not 

susceptible to P toxicity at normal P application rates. Fig. 4.2 also includes added data 

from a further experiment, carried out 5 years later, in which L. ‘Safari Sunset’ plants 

were grown in several different soils (Silber et al. 2003). The plants in the later 

experiment were grown under the same nutritional regime but were planted in four soils 

that differed in their buffering capacity and their native pH, and so induced differing P 

availability in the root environment. The effect of plant-P status on L. ‘Safari Sunset’ 

growth is highlighted by the similarity between results attained under two different 

growth conditions: (1) plants grown in 40-cm deep holes, dug in sandy soil and filled with 

volcanic material, which were exposed to various nutrient application rates (Silber et al. 

2000a); and (2) plants grown under an equivalent nutritional regime in soils that differed 

in their chemical properties (Silber et al. 2003). Furthermore, these findings indicate that 

leaf-P concentration may be used to monitor the P nutritional regime. 

133

Fig. 4.2. Number of marketable branches of L. ‘Safari Sunset’ at the end of the 2nd year 

as a function of leaf-P concentration. The solid line was calculated from the data 

(open circles) of L. ‘Safari Sunset’ grown in Bet Dagan, Israel, during 1994-1995 

and exposed to different nutrient rates in the irrigation water (detailed in Silber et 

al. 2000a). The solid symbols represent data from a different experiment in 

which L. ‘Safari Sunset’ plants were grown during 1999-2000 under an identical 

nutritional regime but were planted in four soils that differed in their buffer 

capacity and the native pH, which induced differing P availability in the root 

environment (Silber et al. 2003). 

The response of two other Leucadendron cultivars (clonal selections of L. 

coniferum and L. muirii) to different P level was also tested by Silber et al. (2000b). The 

development of L. coniferum (L. ‘Orot’) plants under P deficiency (no P added in the 

irrigation water) was significantly superior to that of L. ‘Safari Sunset’ and L. muirii 

cultivars, but as P application increased to 20 mg L -1 , the growth of L. ‘Safari Sunset’ 

became quite similar to that of L. coniferum. No symptoms of P toxicity were observed 

even at the highest P level (20 mg L -1 ) in any of the cultivars tested. Shoot dry weight of 

L. coniferum plants irrigated with tap water was almost three times that of L. ‘Safari 

Sunset’ under the same conditions. Nevertheless, the response of L. coniferum to nutrient 

addition was lower and less significant than that of L. ‘Safari Sunset’. Thus, the dry 

weight (shoots and roots) production of L. ‘Safari Sunset’ fed with an adequate P level 

(20 mg L -1 ) was quite similar to that of L. coniferum plants under the same conditions. 

The dry weight production (shoots plus roots) of L. muirii plants and their response to the 

fertilization treatments were the lowest (Silber et al. 2000b). 

Higher water-N and -P concentrations led to enhanced leaf nutrient status and 

associated increased photosynthesis rates and stomatal conductance in four Leucadendron 

species: L. xanthoconus, L. laureolum, L. coniferum, and L. meridianum (Midgley et al. 

1999). Increased nitrogen application up to 100 mg L -1 progressively increased the yield 

of L. ‘Safari Sunset’ but further nitrogen increases reduced it (Silber et al. 1998; 2000a). 

The NH4-N:NO3-N ratio in the irrigation water is an important factor in ‘Safari Sunset’ 

growth: the yield of NO3-fed plants was low, their leaves were small and their stem 

elongation was inhibited, with a “little-leaf” appearance, compared with those of NH4-fed 

plants (Silber et al. 2000a). These results are consistent with the data of Heinsohn and 

134

Pammenter (1986) for L. salignum grown in water culture. However, in an aerohydroponic 

system at two fixed pHs (5.5 and 7.5) L. ‘Safari Sunset’ growth was not 

inhibited at a low NH4-N:NO3-N ratio (Silber et al. 2000c). The results obtained at fixed 

pH may indicate that the main detrimental effect of a low NH4:NO3 ratio is indirect, e.g., 

via the pH in the root environment (Silber et al. 2000a). 

The potassium concentration in the leaves of L. ‘Safari Sunset’ was found to be 

very low (Cecil et al. 1995; Silber et al. 1998, 2000a,b,c) and below the values considered 

necessary for other ornamental plants (Jones et al. 1991). Sodium concentrations were 

high and exceeded on a molar basis those of K (Silber et al. 1998). The low K 

requirement of the Proteaceae may be attributed to an adaptation to the low-K soils on 

which they originated (Parks et al. 1996; Walters et al. 1991) and that Na may partially 

substitute for K as suggested by Walters et al. (1991). 

Effect of pH on L. ‘Safari Sunset’ Growth. The pH in the rhizosphere is an important 

factor affecting the growth of L. ‘Safari Sunset’ (Ganmore- Neumann et al. 1997; Silber 

et al. 1998, 2000a,c). Silber et al. (2000a) achieved the maximum number of marketable 

branches when the rhizosphere pH was approximately 6.0; below this value, release of 

toxic Mn and Al from soil constituents (Silber et al. 1999) impaired plant development, 

and above it the availability of micro-nutrients was probably too low to provide adequate 

nutrition. Despite the use of chelates, Fe, Zn, and Mn concentrations in the leaves of 

plants grown in high pHs were lower than those in plants grown in acidic pHs, and the 

incidence of “little leaf” attributed to Zn deficiency increased (Silber et al. 2000a,c). 

Whether pH affects the plants directly through physiological mechanisms or indirectly 

through its effects on nutrient availability is not clear. 

Effects of Various Nutritional Regimes on the Growth of Leucadendron Species and on 

Leaf-Nutrient Concentrations. The optimal nutritional regime for a Leucadendron plant 

depends on the nutrient availability in the soil, on the one hand, and on the desired or 

expected yield (number and quality of marketable stems, and the amount of nutrients 

removed by the crop), on the other hand. Most Leucadendron species are not grown in 

commercial fields and data are scarce, but information is available for two cultivars of L. 

salignum × �L. laureolum: ‘Safari Sunset’ in South Australia (Cecil et al. 1995) and in 

Israel (Silber et al. 2003; Shtaynmetz et al. 2004a), and ‘Silvan Red’ in South Australia 

(Barth et al. 1994, 1996; Cecil et al. 1995). Leucadendron is grown in South Australia on 

various soil types, including clay, sandy loam and highly leached sands, with pH values 

between 4.8 and 7.0 (Barth et al. 1996; Cecil et al. 1995). Leucadendron is grown in 

Israel on sandy soils in the coastal plain or in volcanic clayey soils in the north of the 

country (Silber et al. 2003; Shtaynmetz et al. 2004a). The climates of both countries are 

Mediterranean, with cool, wet winters and dry, warm summers. Planting in Australia is at 

a stand of 2600 plants ha -1 , whereas in Israel a much higher stand is used: 6000-6500 

plants ha -1 . Yields and nutrient removal rates by the crops in the two countries are 

summarized in Table 4.6. 

Monitoring nutrient concentrations in plant organs, especially in the leaves, may 

be a useful means of surveying plant growth and optimizing the nutritional regime. 

However, caution is advised when trying to translate analysis data from leaves (or any 

other organ) into agricultural recommendations, because of seasonal variations in the 

chemical composition of leaves (Cecil et al. 1995) and in growth conditions. Two groups 

of published data are available for nutrient values in leaves of Leucadendron plants 

(Table 4.7): (1) data from commercial fields in Australia (Barth et al. 1994, 1996; Cecil et 

al. 1995); and (2) data from nutritional experiments in Israel (Silber et al. 1998, 2000a, 

2000b, 2000c, 2003), Australia (Parks et al. 1996), and South Africa (Heinsohn and 

Pammenter 1986). In addition, the recommendations of the Israeli Extension Service 

(Shtaynmetz et al. 2004a) are included in Table 4.7. Data obtained from commercial 

fields provide useful information on nutrient contents of field-grown plants, but the 

growth conditions are rarely well defined or controlled; therefore, the interpretations and 

the comparison with other data obtained under different conditions may be problematic. 

On the other hand, data obtained from nutritional experiments representing only small 

135

numbers of plants may provide valuable information on nutrient status under wellcontrolled 

conditions in which only a single parameter is varied. Leaf-nutrient 

concentration data from several sources under wide ranges of nutritional regimes and 

growth conditions, including plant ages, are presented in Table 4.7. 

Table 4.6. Accumulation of dry weight and annual nutrient removal per plant or ha basis 

for Leucadendron ‘Safari Sunset’ and ‘Silvan Red’ in South Australia and in Israel. 

Nutrient 

Cultivar DW N P K Na Ca Mg Fe Zn Mn 

kg plant -1 g plant -1 mg plant -1 

Silvan Red z 5 19 2.8 10 25 19 11 450 50 450 

Safari Sunset z 5 28 2.8 14 19 26 9 220 100 500 

Safari Sunset y 2.2 19 5 10 9 6 2 82 10 380 

kg ha -1 g ha -1 

Silvan Red z 1300 4.9 0.7 2.6 6.5 4.9 2.9 117 13 117 

Safari Sunset z 1300 7.3 0.7 3.6 4.9 6.8 2.3 57 26 130 

Safari Sunset y 1360 11.8 3.1 6.2 5.6 3.7 1.2 51 6 99 

z Cecil et al. (1995). 

y Silber et al. (2003). 

4. Response of L. ‘Safari Sunset’ to Irrigation Regime. 

The effect of irrigation regime on the growth of Leucadendron species has been 

examined solely for L. ‘Safari Sunset’ in Israel, where there is a Mediterranean climate, 

with cool, wet winters and dry, warm summers. The harvest period of L. ‘Safari Sunset’ 

in Israel extends from the middle of September (autumn) to the end of April (spring), but 

usually the majority of the yield (80%) is harvested between early October and the end of 

December. The plants are pruned during the winter, and the new vegetation appears as the 

weather becomes warmer around the end of March. Water doses should be adjusted 

according to weather conditions and plant growth; therefore, the recommendations to the 

Israeli growers regarding water application are based on pan evaporation data and plant 

conditions (Shtaynmetz et al. 2004a). The pan coefficient (Kp) for the class A pan 

according to Shtaynmetz et al. (2004a) for adult L. ‘Safari Sunset’ plants is 0.3 (i.e., 2-4 

litres per plant per day) in early April (spring), and it increases progressively to 0.9 (12-14 

litres per plant per day) at the end of July (summer), and then decreases to 0.6-0.8 (6-10 

litres per plant per day) in September-October (fall). Usually, water supply via 

precipitation during the winter (November-February) provides sufficient water for plant 

demands and irrigation ceases. 

Table 4.7. Nutrient concentrations in leaves (Young = youngest leaves on the top of the 

stem; YFEL = youngest fully expanded leaves; Mature = leaves at the bottom of the 

stem; All = all the leaves of several Leucadendron species). 

Macronutrient removal 

(g kg -1 DW) 

Micronutrient removal 

(μg g -1 DW) 

Leaf 

Safari Sunset 

N P K Na Ca Mg Fe Zn Mn 

Young z 9-12 1.2-1.5 5-7 5-7 5-6 2-3 70-100 30-90 150-350 

Young y 10-12 1.0-1.3 3-5 nd 7-10 3-10 60-100 17-25 150-250 

YFEL x 4-12 0.3-1.3 1-4 2-7 2-5 2-3 26-59 11-61 105-313 

Mature 1 12-15 0.5-3.5 6-10 7-11 7-10 1-2 100- 10-90 300-400 

136

350 

All z All 

10-11 2.2-3.5 5-6 6-7 7-8 2-3 80-200 15-70 150-500 

x All 

6 0.6 3 4 5 2 42 19 95 

w Silvan Red 

15 3.5 6 nd 14 7 250 120 280 

YFEL x All 

3-7 0.3-1.3 1-3 3-7 3-6 2-3 22-46 7-34 60-146 

x L. coniferum 

3 0.3 1-2 4-5 3-4 1-2 50-199 8-11 65-75 

(‘Orot’) 18 9.1 7 nd 10 5 nd nd nd 

All v 

Sundance 

Mature u 10-22 0.5-1.1 6-10 nd nd nd nd nd nd 

L. salignum 

All t 20-30 0.6 7-12 nd nd nd nd nd nd 

z 

Silber et al. (2003) 

y 

Shtaynmetz et al. (2004a) 

x 

Cecil et al. (1995) 

w 

Silber et al. (2000a) 

v 

Silber et al. (2000b) 

u 

Parks et al. (1996) 

t 

Heinsohn and Pammenter (1986) 

Silber et al. (2003) examined the effect of irrigation dose and frequency on L. 

‘Safari Sunset’ grown in clayey soil of volcanic origin in the Golan Heights. The daily 

global irradiance and pan evaporation data (calculated per plant) from the experimental 

site are presented in Fig. 4.3. The maximum water application rate (100%) was defined as 

the water dose required to fulfill plant demands without any stress, and was monitored 

with tensiometers located around the plants at various distances and with phytomonitors. 

It was found that young plants (1-3 years after planting) responded positively to increased 

irrigation doses, and significant linear regressions were obtained between the biomass 

production of the shoots, on the one hand, and the water dose applied and the soil water 

content, on the other hand (Fig. 4.4). The positive effect of increased water amount on 

biomass production of L. xanthoconus was reported by Davis, Flynn, and Midgley (1992). 

However, in the fourth year, after the space between plants had been covered entirely 

(6200 plants ha -1 ), the irradiation became the limiting factor for shoot growth, and the 

yield was no better under the highest water doses (100%) than under a lower rate (70%). 

Irrigation dose did not affect the number of marketable stems but significantly affected 

their quality. The diameter of the “flower heads” of plants exposed to low irrigation doses 

was small, and it increased progressively as the irrigation dose increased (Fig. 4.5). From 

the marketing point of view, this effect is extremely important in light of the dominant 

role of the ‘flower head’ dimension on the price of L. ‘Safari Sunset’ stems in the cut 

flower markets. 

5. Overcoming Soil Problems in Cultivating L. ‘Safari Sunset’ in Israel. 

The two parents of Leucadendron ‘Safari Sunset’ are native to South African soils 

that have low pH. However, in Israel, despite the suitable climate, growers of proteas 

have encountered problems because of unfavorable soil characteristics, such as high pH 

and high free-lime content. Two agro-technical methods are feasible for overcoming these 

soil limitations (Silber and Ben-Jaacov 2001): (1) improvement of the rhizosphere 

conditions; and (2) grafting sensitive cultivars onto resistant rootstocks. 

137

Fig. 4.3. Meteorological data of three years from the experimental site in the Golan 

Heights: (top) global irradiation, and (bottom) pan evaporation calculated for 

single plant (6200 plants ha -1 ). 

138

Fig. 4.4. Total fresh weight production (not including roots) of ‘Safari Sunset’ plants (3 

years after planting) as a function of: (left) annual water application (L/plant), 

and (right) soil water content (mL g -1 soil) * 100. 

Fig. 4.5. Effect of water application doses on the “head” diameter of ‘Safari Sunset’ plants 

(3 years after planting). I1: irrigation doses that fulfill all plant demands during 

the season, without any stress; I2: 70% of I1; and I3: 40% of I1 (from Silber et 

al. 2003). 

Improvement of the Rhizosphere Conditions. The common horticultural practice in Israel 

is to improve the rhizosphere conditions in a restricted volume of the root zone by using a 

small volume (30-50 litres) of artificial substrate and/or by employing nutritional 

management that reduces the pH. Leucadendron ‘Safari Sunset’ is often planted in tuff 

(volcanic material), which is placed in holes dug in the native soil, or on the soil as a 

small pile. Usually, there are no barriers to the free extension of roots from the tuff into 

the native soil, and the roots develop under two different environments: (1) a 

predetermined volume (usually 30-50 L) in the vicinity of the plant, where the tuff 

properties ensure suitable drainage and pH conditions for plant growth; and (2) the 

surrounding native soil, where air deficiency or high pH may restrict plant development. 

Examination of roots at the end of the second year of L. ‘Safari Sunset’ growth 

139

demonstrated that at least 80% of the root system was located in the tuff (Silber et al. 

2000a). The root system in the tuff was healthy and white with good branching, whereas 

that in the soil was restricted and brown with poor branching. The use of artificial 

substrates and of modern irrigation and fertilization equipment enables the appropriate 

conditions to be provided for plant growth and facilitates control of the rhizosphere pH. 

Reducing the soil pH through addition of acids via the irrigating solution is almost 

ineffective and is not recommended, whereas an indirect approach, such as modifying the 

rhizosphere pH by choice of the N source is more likely to succeed. The nitrogen source 

affects the rhizosphere pH via three mechanisms (Marschner 1995; Marschner and 

Romheld 1996): (1) displacement of H+/OH- adsorbed on the solid phase; (2) 

nitrification/denitrification reactions; and (3) release/uptake of H+ by roots in response to 

NH4/NO3 uptake. Mechanisms 1 and 2 are not associated with any plant activity, and 

affect the whole volume of the fertigated soil, but mechanism 3 is directly related to the 

uptake of nutritional elements and may be very effective because it affects a limited 

volume of soil in the immediate vicinity of the roots. Obviously, in addition to the above 

indirect effect, the nature and concentration of the irrigation-N source may have direct 

effects on plant growth, on chlorophyll content in leaves, and on chlorosis incidence 

(Mengel and Kirkby 1987; Marschner 1995). Use of a high NH4:NO3 ratio and 

appropriate nutritional management are common means for achieving desirable pH and 

ion concentrations in the tuff medium (Fig. 4.6), and hence for improving L. ‘Safari 

Sunset’ growth (Silber et al. 1998). 

Grafting Sensitive Cultivars onto Resistant Rootstocks. The use of rootstocks in 

cultivating Proteaceae was suggested as early as 1966 by Rousseau (1966), but has been 

commercially adopted only during the last two decades (Ben-Jaacov et al. 1992). Some 

species, native to highpH soils in South Africa, were studied as potential rootstocks in 

Israel in the late 1980s. As a result of these studies, several clones and species were 

selected and the best results were achieved by using a clonal selection of L. coniferum, 

which was named ‘Orot’, and by propagating L. galpinii. The possibility of improving 

plant production by using the two alternatives simultaneously, i.e., growing L. ‘Safari 

Sunset’ grafted on a resistant rootstock in a tuff medium under optimal nutritional 

management, was proposed as the most promising method. Several studies have shown 

that the growth of grafted plants was significantly superior to that of ungrafted plants, and 

that this advantage was more significant under conditions of nutrient deficiency and nonoptimal 

pH. 

Fig. 4.6. The effect of NH4-N:NO3-N ratio on pH in leachates from growth containers 

with ‘Safari Sunset’ plants (adapted from Silber et al. 2000a). 

140

6. Control of Growth and Flowering - Pruning and Pinching. 

Efficient pruning to maximize yield is essential, and is a specialized operation in 

Leucadendron. Brits et al. (1986) first attempted to give systematic, general guidelines for 

commercial pruning of proteas, including Leucadendron. The growth cycle of 

leucadendrons depends on the season. 

They sprout in the spring, slow down their growth through the summer, and then 

initiate flowers. The reason for the cessation of growth, for flower induction, and for the 

development of the colorful involucre leaves is unknown. Pruning in done mainly by 

picking the flowers at harvesting time (Mathews 1982; Brits et al. 1986). Leucadendrons 

will take heavy pruning; therefore, the shrubs can be kept tidy and shaped to any 

particular need. Ben-Jaacov and Kadman-Zahavi (1988) showed that the imposition of 

long days at the end of the summer delayed flower development in Leucadendron 

discolors. At high elevation in Ecuador (latitude 0°), growth and flowering of L. ‘Safari 

Sunset’ continue year round (S. Pollack, pers. commun. 2004). 

Like other proteas, leucadendrons may be divided into two groups; sprouters and 

seeders. The sprouters, which have a lignotuber, will recover easily after heavy pruning, 

whereas seeders, if pruned heavily, i.e., down to heavy wood that has already lost its 

leaves, will not sprout (Brits et al. 1986). Most leucadendrons are shrubs, but the silver 

tree (L. argenteum) is a tree and if allowed to grow straight up it will reach a height of 10 

m. It can, however, be restricted to a height of 4-6 m if tip pruned in the first, second, or 

third year, and it will then cover a diameter of 4-5 m (Mathews 1982). However, if this 

tree is pruned down to old branches that lack foliage, it will not sprout. 

The yield and seasonal growth flushing of Leucadendron ‘Silvan Red’, in South 

Australia, were studied by Barth et al. (1996). They indicated that in South Australia L. 

‘Silvan Red’ produces two types of products: in fall stems that terminate in red “flower 

heads” are harvested, but stems can remain on the bush to be harvested in the winter with 

tricolor (yellow-red-green) “flower heads.” The use of soft pinch in the springtime 

doubled or even tripled production, by the growth of two to four more branches on each 

pinched stem. It is important to pinch only stems that are at least 10 mm in diameter at the 

base (Wolfson et al. 2001). When pinching is done later in the summer, some of the 

branches develop into good-quality multi-headed stems, but most of the stems originating 

in the middle of the summer are of poor quality, many of them of the “little leaf” type (see 

E2, Wallerstein et al. 1989; Wolfson et al. 2001). Lahav et al. (1997) indicated that the 

last date for soft pinch of L. ‘Safari Sunset’ grown in the coastal region of Israel is at the 

end of May or beginning of June. The current recommendation for L. ‘Safari Sunset’ in 

Israel is to prune heavily in the first two years in order to branch the young plants. Later 

the commercial pruning is done by harvesting and corrective pruning in the early spring 

(Shtaynmetz et al. 2004a). 

E. Plant Protection 

1. Diseases. 

In the recent book by Crous et al (2004) there is excellent information regarding 

Leucadendron diseases. In addition there are 2 booklets devoted entirely to protea 

diseases (von Broembsen 1989; Forsberg 1993). In addition, Swart (undated) of the 

Fynbos Unit in South Africa compiled information on the main Protea diseases in South 

Africa, including the following diseases that attack Leucadendron: Phytophthora 

cinnamomi (Pc) commonly called “root rot”, “crown rot” or “collar rot”, Fusarium 

oxysporum commonly called “wilt”, Elisinoe spp. commonly called, “scab” or “corky 

bark”, Botryts cinerea commonly called “flower head blight”, Coleroa senniana 

commonly called “coleroa leaf spot”, Batcheloromyces proteae and B. leucadendri 

commonly called “batcheloromyces leaf spot”, Cerostigmina protearum var. protearum, 

and C. protearum var. leucadendri commonly called “stigmina leaf spot”, and Vizella 

interrupta commonly called “five o’clock shadow disease”. In much of the literature, 

leucadendron diseases are addressed together with diseases of other genera of proteas. 

141

Leucadendrons are often infected with fungal diseases of the stems and roots as well as 

several post-harvest diseases, which are generally caused by widespread fungi with little 

host specificity. On the other hand, diseases of the leaves are generally caused by 

Leucadendron-specific pathogens, many of which originated in South Africa. Protea 

pathogens in South Africa are fairly well documented (Knox-Davies et al. 1986, 1987, 

1988) but little is known about pathogens of South African Proteas cultivated elsewhere 

in the world. Taylor (2001) has recently surveyed all such pathogens in Australia, South 

Africa, U.S.A., and Zimbabwe, in light of the recent changes in the phytosanitary 

regulations, ratified by the World Trade Organization (World Trade Organization 1994). 

Taylor concluded that many of the pathogens that originated in South Africa are already 

widespread and have varying degrees of importance in other countries. However, other 

pathogens have been recorded only in South Africa, and measures must be taken to 

prevent their spread. Different pathogens assume greater or smaller importance in some 

countries or regions than in others. 

South African proteas and especially leucadendrons originated in areas of winter 

rainfall, and when planted in wet and humid parts of the world, where summer rainfall 

prevails, they are very susceptible to many fungal diseases. Phytophthora root and collar 

disease, caused by the fungus Phytophthora cinnamomi (Pc), is probably the most serious 

soil-borne disease of Leucadendron (Von Broembsen and Brits 1985). Pc has an 

extremely wide host range and has a worldwide distribution (Von Broembsen and Kruger 

1985) but, nevertheless, the economic pressure of this fungus on the commercial 

production of Leucadendron as cut flowers varies greatly with the location. For instance, 

Forsberg (1993) pointed out that Proteas grown in Queensland are more susceptible to 

this fungus than those grown in southern states of Australia. This variability may occur 

because the pressure of this disease is greater in summer rainfall areas (Zentmyer et al. 

1994; Zentmyer 1980), or because the type of Phytophthora (A2 type) that is dominant in 

Australia is more virulent than the type (A1) that affects proteas in South Africa 

(Forsberg 1993). A survey of wild flower farms in the south-west of Western Australia 

identified two other species of Phytophthora that attack Leucadendrons: P. citricola and 

P. cactorum (Boersma et al. 2000). 

Phytophthora cinnamomi has been rarely identified on Leucadendron- infected 

plants in Israel. Several other soil-borne fungi: Fusarium solani and Pythium Sp. were 

identified as causing death of Leucadendron plants (Ben-Yephet et al. 1999). The 

difficulties in identifying the exact cause of a sudden death of mature Leucadendron 

plants can be seen in a report from New Zealand: Soteros and Dennis (undated) described 

two wilt disorders that caused concern to leucadendron growers in some areas of the 

southern parts of New Zealand’s North Island; both are commonly called “wiri wiri” wilt 

by growers. One disorder was indeed root rot disease, caused by Pc; it was reported to be 

active mainly when soil conditions were warm and moist. The other disease, which they 

called “waitara” wilt, initially displayed similar leaf symptoms to the root rot disease 

caused by Pc, but as Soteros and Dennis (undated) indicated, it is a different disease, 

which affected only the cultivars ‘Safari Sunset’, ‘Red Gem’, and L. laureolum; it does 

not affect the root system and is evident mainly during production of the bracts, from 

autumn to winter. Although chemical spray reduced the spread of the disease, the cause of 

the disorder has not been identified. Phytophthora dieback, or as it called in Western 

Australia “protea sudden death”, is still a major problem and is, therefore, currently being 

investigated in many places (Dieback Working Group 2000; Duncan and Dunne 2000). 

The occurrence of Pc on silver trees was reported as early as 1973 (Van-Wyk 

1973).The occurrence of Pc on indigenous (Von Broembsen and Kruger 1985) and exotic 

hosts in South Africa has been reported by Von Broembsen (1984). There are four main 

ways to avoid or overcome sudden death (Pc) of Leucadendron (Brits and von Broembsen 

1978; von Broembsen and Brits 1986): (1) plant only on well-drained soil and avoiding 

over-watering; (2) sanitation: prevent the presence of the fungi in the nursery, in the soil 

of the plantation, and in the water used for irrigation; (3) use of chemical (Turnbull and 

Crees 1995; Marks and Smith 1990, 1992), biological (Turnbull et al. 1989), and 

142

iofumigant (Duncan and Dunne 2000) methods to control the disease; and (4) use of 

resistant plant material and/or grafting the desired cultivar on a resistant rootstock. Von 

Broembsen and Brits (1985) found that L. argenteum and L. salignum were very sensitive 

to Pc, whereas L. nervosum and L. uliginosum were resistant. Turnbull (1991) and Moffatt 

and Turnbull (1994) found that L. eucalyptifolium and L. xanthoconus were resistant, 

whereas L. procerum and L. ‘Silvan Red’ were very sensitive. Cultivars and rootstocks 

can be evaluated for resistance to Pc by several methods, such as stem inoculation 

techniques (Denman and Sadie 2001). In irrigation experiments conducted in Israel, 

Silber et al. (2003) observed that under intensive watering treatments more L. ‘Safari 

Sunset’ grafted on L. ‘Orot’ died from soil-borne diseases than those grown on their own 

roots. Although Pc, when present, is the main killer of Leucadendron, many other fungi 

are often found on dying plants, on rooting cuttings, and on young seedlings in the 

nursery. Among these are: Armillaria (Forsberg 1993), Fusarium solani, and Pythium 

spp. (Ben-Yephet et al. 1999), and Fusarium oxysporum (Benic 1986). Anthracnose, 

caused by Colletotrichum gloesporioides, is known in Protea and Leucospermum, but 

Leucadendron was recorded as being resistant to this disease (Knox- Davies et al. 1986). 

Moura and Rodrigues (2001) reported that Rosellinea necatrix was the “most frequent” 

soil fungus found on roots of Leucadendron in the Madeira Islands and indicated that the 

cultivars ‘Safari Sunset’, ‘Long Tom’, ‘Inca Gold’, and ‘Wilson Wonder’ are very 

susceptible to the disease, whereas ‘Pisa’, ‘Silvan Red’, and ‘Rising Sun’ seem to be more 

tolerant. They also identified Fusarium solani and Rhizoctonia solani among the root 

diseases present in Leucadendron in Madeira Island. Dunne et al. (2003) surveyed 28 

protea plantations in southwest parts of Western Australia and were able to isolate Pc in 

11 of them. In other plantations, Protea death and decline were attributed to other fungal 

pathogens, including Fusarium, Botryosphaeria, and Pestalotiopsis, as well as to 

nutritional disorders and physical factors. Leaf and shoot diseases are very common on 

proteas (Doidge and Bottomley 1931) and are less common on Leucadendron (Doidge 

1950). 

Schizophyllum commune has been reported to cause “trunk rot” in Leucadendron 

argenteum (Doidge 1950), and Van-Wyk (1973) reported that Botrryosphaeria ribis 

caused branch die-back on L. argenteum. The scab disease caused by Elsinoe is a very 

serious disease of Leucospermum (Forsberg 1993), however it has been reported also on 

several Leucadendron species (Forsberg 1993). In 1985 Van-Wyk et al. (1985a) reported 

the identification of Helicosingula as a new genus of fungi that attacks Leucadendron 

tinctum, and they found Batcheloromyces leucadendri on other Leucadendron spp. (Van- 

Wyk et al. 1985b) in South Africa. In humid climates, Botrytis blight (B. cinerea) has 

been reported to damage leucadendrons (Serfontein and Knox-Davies 1990; Forsberg 

1993; Moura and Rodrigues 2001). Silver leaf caused by the fungus Chondrostereum 

purpureum has been reported from New Zealand but has not been detected on 

Leucadendron in Australia (Forsberg 1993). Lasidiplodia, Botyodiplodia, Phomopsis, and 

Botryosphaeria may cause rotting, mainly of wounded or weak branches (Forsberg 1993). 

Moura and Rodrigues (2001) isolated Pestalotia guepini, Phoma glomerata, and 

Stemphylium botryosum from Leucadendron in Madeira. The only fungi that were 

reported to cause leaf and stem diseases on L. ‘Safari Sunset’ in Israel are Lasidodiplodia 

(known in Israel as diplodia), which mainly attacks wounded and weak stems, and 

Alternaria, which has been reported as a storage disease (Shtaynmetz et al. 2004b). In 

Australia, several leaf and shoot diseases have been reported to attack leucadendrons 

(Crous and Palm 1999; Crous et al. 2000). Elsinoe scab causes substantial economic 

losses to proteas including leucadendrons in Australia; a survey showed the most severely 

affected species and cultivars to be (in descending order): Leucadendron ‘Silvan Red’, L. 

‘Safari Sunset’, Leucospermum cordifolium, Leucadendron laureolum, Leucospermum 

tottum ‘Firewheel’, Leucadendron ‘Inca Gold’, Leucadendron ‘Red Gem’, and Serruria 

florida (Pascoe et al. 1995) 

143

2. Physiological Disorders. 

The “little-leaves” phenomenon in L. ‘Safari Sunset’ is well known in Israel 

(Lahav et al. 1997; Wallerstein et al. 1989; Wolfson et al. 2001; Silber et al. 2003), 

although this physiological disorder has not been described in the international literature. 

The leaves along the shoot are small, most of the buds situated at the axes of these leaves 

are somewhat elongated, and in the autumn the ends of the stems terminate in small 

involucre leaves without real flower heads. The exact cause of this phenomenon is not 

well known, but it is enhanced by one or several stress conditions: pruning or pinching in 

the middle of the summer (Lahav et al. 1997; Wolfson et al. 2001), high soil pH (Silber et 

al. 2000a), insufficient irrigation (Silber et al. 2003), and insufficient light (Wallerstein et 

al. 1989). This phenomenon could have been a result of Zn deficiency as hypothesize by 

Silber et al (2000a), however direct evidence is missing. 

3. Insects. 

Insects are a relatively minor problem in Leucadendron cultivation. Most 

publications related to insects as pests of Proteaceae address the subject in general and are 

not specific for Leucadendron (Coetzee et al. 1997; Zachariades and Midgley 1999; 

Leandro et al. 2003; Wright 2003). Wright (2003) reviewed pests that attack Proteaceae 

around the world (Table 4.8). It is clear that the greatest problems with insects are in 

South Africa, so it is very important to try to prevent the entry of these insect into other 

Protea-producing countries. Leandro et al. (2003) were more specific, and indicated the 

insects they found on leucadendrons grown in southwest Portugal: Helicoverpa armigera 

and Cacoecimorpha pronubana were found on shoots and flowers; Sesamia nonagrioides 

attacked the stems of young plants; scales and mealybugs damaged stems and leaves; and 

aphids attacked shoots of leucadendrons. Wright (undated) described the following 

insects that attack leucadendrons in South Africa: Epichoristodes acerbella (Lepidoptera: 

Tortricidae), commonly known as “Carnation worm” and Phyllocnistis spp. 

(Lepidoptera: Phyllocnistidae), commonly known as “Channel leaf miner”. 

Table 4.8. Major pest groups found on South African proteaceous species, grown in 

different countries. 

Pest group 

S. 

Africa Australia 

New 

Zealand 

USA 

(Calif.) 

USA 

(Hawaii) Zimbabwe 

Bud borers xx z 

x 

Stem borers xx x x x 

Root borers x 

Leaf minors 

Leaf chewers 

xx 

x 

x x 

x x x 

x 

Scale insects xx x x x x 

Mealybugs xx x 

Thrips x x x 

z 

xx = severe pest, x = occasional/moderate pest (Revised from Wright 2003). 

4. Nematodes. 

Root knot nematodes can be a major problem with some proteas under certain 

climatic and soil conditions (Cho and Apt 1977). These works screened several species of 

proteas, leucospermums, and leucadendrons for resistance to the nematode Meloidogyne 

incognita, and found that, in general, Leucadendron is more resistant than the other two 

genera. Among leucadendrons, L. argenteum and L. discolor were resistant to the 

nematode, whereas L. laureolum and L. uliginosum were more susceptible. 

144

5. Weeds. 

Uncontrolled weeds in Leucadendron plantations are harmful. Weed control is 

important, since Leucadendrons have shallow roots that can be easily damaged by handhoeing. 

Therefore, it is recommended to install woven ground cover in the planting rows. 

Between the rows, mechanical weed control may be applied, whether the ground is tilled 

or untilled. If it is untilled, the weeds may be mowed (a common practice in New 

Zealand), or they can be controlled chemically (DeFrank and Easton-Smith 1990). It is 

recommended for L. ‘Safari Sunset’ in Israel to spray in the fall, using Goal (oxyfluorfen) 

at 1000 g/ha + Simazine at 2000 g/ha, against winter weeds, and to use nonselective weed 

killers in the summer (Shtaynmetz 1998). 

F. Post Harvest Studies 

1. Handling and Storage. 

In general, Leucadendrons have very long shelf lives. Storage, if done properly, 

can be continued for long periods without any reduction in the shelf life of the flowers. 

For these reasons, there have been relatively few attempts to improve their storage or vase 

life. With the increased importance of sea transport, several studies were done, in 

attempts to improve vase life after long periods of dry storage. Jones and Faragher (1991) 

and Jones (1991) reported that L. ‘Silvan Red’ maintained a commercially acceptable 

vase life of 19 days even after 49 days of storage. Pulsing L. ‘Silvan Red’ stems with 

sucrose solutions at a concentration of 200 g L -1 (20%) or higher for 24 h at 1°C 

prevented leaf desiccation during 42 days of dry storage at 1°C (Jones 1995). Street and 

Sedgley (1990) showed that water stress was the main factor that reduced the vase life of 

L. ‘Silvan Red’. 

In the last few years, the Israeli growers have been sending about 75% of their 

yearly 30 million L. ‘Safari Sunset’ stems to Europe by sea (Gazit 2002). The duration of 

the transport is 10 days, from the producers’ packing house to the Aalsmeer Auction 

floor. Meir et al. (2000) were able to store L. ‘Safari Sunset’ successfully even for 6.5 

weeks. The post harvest procedure for sea transport, as recommended by the Israeli 

Research and Extension Service (S. Philosoph-Hadas and S. Meir, pers. commun., 2002; 

Shtaynmetz et al. 2002, 2004b), includes the following steps and precautions: (1) harvest 

and ship only ripe and lignified, healthy and undamaged stems; (2) place the stems in 

water containing organic chlorine or simply hydrochlorite; (3) cool the stems at 2-5°C for 

24 hr; (4) after sorting the stems, pulse them with 0.5% TOG 4 (containing 8-HQC, citric 

acid and surfactants) or 0.1% TOG 3 (containing 8-HQC, TBZ, glycolic acid and 

surfactants); (5) cool the stems in the above solution for 12-24 hr; and (6) dry the foliage 

and the stems well before placing them in the shipping boxes. 

However, even when the above procedure is used, problems have occurred from 

time to time (un-predicted and irregular), involving dry or rotting stems (sometimes only 

a few in a bunch). The main causes for these problems were identified as diseases, mainly 

Alternaria but sometimes Clodosporium, Fusarium, or Diplodia; physiological stresses; 

and physical injuries that stimulate the diseases. After a humid summer, the damage 

caused by Alternaria was the most serious. To overcome the above fungal diseases, it was 

recommended to apply preventive sprays in the plantations and/or in the packing house, 

to fumigate the cut stems in the cold rooms, and to remove all physically damaged tissues. 

Physiological stresses may be caused by freezing and/or by overheating if stems are not 

cooled down sufficiently before putting them in the shipping boxes or in case of a failure 

in the cooling chain. The main conclusion was that careful observance of the above 

recommendation would eliminate the arrival of damaged stems to the markets 

(Shtaynmetz et al. 2002, 2004a,b). 

Prolonged storage may be needed not only for sea shipping, but also to regulate 

the market and to ensure uniformity of the product over a long time. The involucral leaves 

of the Israeli L. salignum selection ‘Yaeli’ turn yellow about one month before Easter, 

and in order to be able to market the yellow flowering stems during Easter, (S. Meir pers. 

145

commun., 2002) stored the yellow flowering stems for one month. At the end of the 

storage period, the stored stems bore nice yellow involucral leaves, whereas the stems 

harvested during Easter carried less attractive, green involucral leaves (Shtaynmetz et al. 

2000; S. Meir, pers. commun., 2002). 

2. Insect Eradication. 

Leucadendrons are produced in open field plantations, therefore it is difficult to 

achieve 100% control of insects, especially if the production is under wild or semi-wild 

conditions, so that it is sometimes necessary to eradicate insects from the harvested cut 

branches after harvesting and before marketing. This can be done by chemical treatments 

or by hot-air disinfestation. In a recent study, it was found possible to achieve control of 

quarantine pests, including thrips and armored scales, with a hot-air treatment (Hara et al. 

2003). The following protocol was recommended for cut branches of Leucadendron 

‘Safari Sunset’: increasing the temperature gradually, starting at 39°C for 15 min and at 

41°C for 15 min, both at RH of 60-75%, then the eradication treatment at 44°C and RH 

60% for 1 hr. This treatment controlled the insects, did not damage the foliage, and did 

not impair shelf life (Hara et al. 2003). 

146 

G. Leucadendron as a Pot Plant 

Woody flowering plants have potential for use as flowering pot plants (Ben- 

Jaacov et al. 1989b). There is a continuous introduction and development of new woody 

flowering pot plants (Tal et al. 1994). There is no problem in being able to produce large 

flowering plants in large pots or tubs, but transport and marketing considerations make 

the production of such plants uneconomical, and the production and marketing of small 

(in pots up to 15 cm in diameter) woody flowering pot plants present a challenge. Of all 

the proteas, plants from only three genera are currently being marketed as small flowering 

pot plants; they are Serruria (Brits 1995), Leucospermum (Criley 1998), and Grevillea 

(Tal and Ben-Jaacov 1988). There have been only a few attempts to study and produce 

small flowering pot plants of Leucadendron. To overcome the difficulties in inducing 

flowers on young Leucadendron plants in small pots, Ben- Jaacov et al. (1986) attempted 

to use the “Rapid Production System”, which involves the rooting of induced, large, and 

branched cuttings. This system, which had been suggested several years earlier by Jacobs, 

Brits and others, was finally developed for Leucospermum by Ackerman and Brits (1991), 

and Ackerman et al. (1995), who found it possible to root large, branched, and induced 

cuttings of Leucadendron discolor. The best flowering occurred on cuttings taken 

between Nov. 21 and Dec. 25 (in the Northern hemisphere). In cuttings taken earlier, the 

percentage of flowering terminals was low; some did not initiate flowers and many of the 

flowers that were initiated aborted or reverted to vegetative growth. The stress placed on 

the plants during the rooting period resulted in the production of low-quality potted plants 

(Ben-Jaacov et al. 1986). 

Tal and Ben-Jaacov (1988) attempted to produce L. discolor and L. ‘Safari Sunset’ 

as flowering pot plants in small (10 cm diameter) pots by using conventional methods of 

production. They planted 3-month-old rooted cuttings in 10-cm pots, and studied the 

effects of the growth retardants paclobutrazol and diaminozide in retarding shoot 

elongation. Two weeks after planting, all the shoots were cut back to two-bud branches. 

After a further two weeks, when the new growth had reached about 1 cm, the young 

plants were sprayed or drenched with the growth retardants. Both chemicals and methods 

of application were effective in dwarfing the plants. However, since the plants never 

flowered in the small pots, the project was terminated.

V. CROP POTENTIAL AND RESEARCH NEEDS 

Leucadendron is probably one of the best decorative foliage plants available in the 

flower market. Its product characteristics (Coetzee and Littlejohn 2001) are excellent, 

branches have a very long shelf life, measured in weeks; it can be easily shipped by sea 

and can travel for at least 10 days; and its stems are straight, making it very easy to pack 

efficiently. Many of the species and cultivars are sold as foliage and can be marketed 

almost the year round. The color of the foliage ranges from bronze-red through yellow to 

various shades of green and silvery gray. Some of the species and cultivars present greater 

difficulties than others in marketing, especially male cultivars that are marketed at their 

flowering time, for example, male L. discolor, characterized by rapid flower senescence 

leading to very short shelf life. However, the selection of early, mid-season, and late 

cultivars could extend the production and marketing period of this beautiful flower. 

The production characteristics of Leucadendron (Coetzee and Littlejohn 2001) are 

also almost perfect: the yield is much higher than that of any other protea; most species 

and cultivars have very vigorous growth; production starts from a young age, and the 

plantations can have a fairly long life. Most species and cultivars are tolerant of low and 

high temperatures, and if planted under suitable conditions the plants are relatively 

resistant to diseases and pests. Nevertheless, growers and researchers can do much to 

further the prosperity and continued expansion of the leucadendron industry. Aspects 

worthy of attention include: genetic improvement; diversification of leucadendrons; 

continuous development and improvement of the agro-technology; and increased public 

awareness of this wonderful flower. We should conserve all the available genetic 

variability to ensure the possibility of future improvement (Littlejohn et al. 2000). Genetic 

improvement may be achieved through advances in breeding technology and through the 

use of a wider range of interspecific hybrids, and also by mutation breeding. Sub-clonal 

selections have already led to the development of some excellent cultivars, e.g., the 

variegated L. ‘Safari Sunset’ named ‘Jester’ (Sadie 2002), and the Israeli improved L. 

‘Safari Sunset’ named ‘Petra’ (S. Kadosh, pers. commun., 2003). Increasing the selection 

of leucadendrons available in the market is an important way to increase the total sales 

volume. There is a need to develop cultivars specifically suited for the production of 

potted plants, and research is needed for the development of the appropriate technology. 

There is very little knowledge of the mechanisms of flower induction and 

development, and greater knowledge of how to control growth and flowering is needed 

for many reasons. In modern intensive production of L. ‘Safari Sunset’, an excess of shoot 

length is produced, which is wasted. This is because the achievement of high-quality, 

large flower heads in this cultivar demands a high level of irrigation, which also leads to 

excessively long shoots (Silber et al. 2003). Thus, the question is how to produce the 

large flower heads without producing excessively long stems. For better and more 

profitable marketing, it is important to improve selling standards. There is an attempt in 

Israel to sort and market L. ‘Safari Sunset’ according to the size of the “flower head”. 

Growers and machinery manufacturers are now working on the development of a sorting 

machine based on photographic image processing (S. Kadosh, pers. commun. 2004). It is 

hoped that this machine will help to ensure the marketing of more uniformly high-quality 

flowers in an efficient way. There is a need to increase leucadendron production 

efficiency, and there is now a joint effort in Israel to develop a pruningharvesting machine 

(Lev et al. 2004). Production and marketing technology of L. ‘Safari Sunset’ is already 

advanced, and it is important to extend this production technology to other Leucadendron 

cultivars. 

ACKNOWLEDGMENT 

This paper is contribution No. 617/04 of the Agricultural Research Organization, 

the Volcani Center, Israel. 

147


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