hydrilla: Hydrilla verticillata (Hydrocharitales: Hydrocharitaceae): Invasive Plant Atlas of the United States

hydrilla	USDA PLANTS Symbol: HYVE3 U.S. Nativity: Exotic Habit: Aquatic Plants
Hydrilla verticillata (L. f.) Royle

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Taxonomic Rank: Liliopsida: Hydrocharitales: Hydrocharitaceae
Synonym(s): Florida elodea, water thyme, waterthyme
Native Range: Europe; Old World (BAIL);
Appearance Hydrilla verticillata is a submersed, rooted aquatic plant that can grow in water up to depths of 20 ft. (6.1 m). Plants can survive in depths up to 40 ft. (12 m) in non-turbid water. Foliage Leaves are whorled in bunches of 3-8, but most often with whorls of 5. The midribs of the leaves are reddish in color with the undersides having small, raised teeth. Leaves are 0.2-0.8 in. (5-20 mm) long, less than 0.1 in. (2 mm) wide and have serrated margins. Flowers Only the female flowers of this dioecious plant have been found in the United States, which means no viable seed are produced. Fruit Turions (stem tubers) are bud-like structures which can drop off the plant and successfully survive freezing or drought. Tubers from the rhizomes are another way these plants reproduce and increase their invasive potential. Ecological Threat Hydrilla verticillata forms dense mats at the surface of the water. The dense mats can restrict native vegetation, irrigation practices, recreation, hydroelectric production, and water flow. It can invade most slow-moving or still water systems. This plant is believed to be native to Asia or Africa, although it is widely spread across the globe. It was first introduced into North America as an aquarium plant in the 1950s.

Identification, Biology, Control and Management Resources

Fact Sheet - Ontarios Invading Species Awareness Program
Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
Southeast Exotic Pest Plant Council Invasive Plant Manual - SE-EPPC
Element Stewardship Abstract - The Nature Conservancy
Federal Noxious Weed Disseminules of the U.S. - USDA-APHIS
Weed of the Week - USDA Forest Service
Global Invasive Species Database - Invasive Species Specialist Group
Plant Invaders of Mid-Atlantic Natural Areas - National Park Service and U.S. Fish and Wildlife Service

Selected Images from Invasive.org

View All Images at Invasive.org

Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage	Plant(s); USDA APHIS PPQ - Oxford, North Carolina , USDA APHIS PPQ, Bugwood.org Additional Resolutions & Image Usage	Plant(s); Discovered in the Crystal River in south Florida in 1960. Raghavan Charudattan, University of Florida, Bugwood.org Additional Resolutions & Image Usage	Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage
Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage	Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage	Plant(s); David J. Moorhead, University of Georgia, Bugwood.org Additional Resolutions & Image Usage	Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage

EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org