Eurasian watermilfoil
Myriophyllum spicatum L.

Overview

Appearance

Myriophyllum spicatum is a submersed aquatic plant that invades lakes, ponds, and other aquatic environments throughout the United States. The plants are rooted and the stems grow up to the water surface, usually reaching 3-10 ft. (0.9-3 m) in length and can be as much as 30 ft. (9.1 m) long.

Foliage

Leaves are bright green, finely dissected, and whorled. The delicate leaflets give this plant a feathery appearance.

Flowers

Myriophyllum spicatum has both male and female flowers on the same inflorescence. The female flowers are basal while the male flowers are located distally. The female flowers have a 4-lobed pistil and lack sepals and petals. The male flowers have 4 pink petals and 8 stamens.

Fruit

The very small globular fruit of Myriophyllum spicatum are indehiscent, and contain 4 seeds.

Ecological Threat

Myriophyllum spicatum requires stagnant to slowly moving water and can tolerate brackish conditions. It forms dense mats of leaves restricting light availability, leading to a decline in the diversity and abundance of native macrophytes. In addition, Myriophyllum spicatum displaces the native species of watermilfoil and reduces habitats for fish spawning and feeding. It is native to Europe, Asia, and northern Africa.

Resources

• Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
• Southeast Exotic Pest Plant Council Invasive Plant Manual - SE-EPPC
• Plant Invaders of Mid-Atlantic Natural Areas - National Park Service and U.S. Fish and Wildlife Service
• Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
• Global Invasive Species Database - Invasive Species Specialist Group
• Images, Video and Information - University of Florida - Center for Aquatic and Invasive Plants
• Fact Sheet - Ontarios Invading Species Awareness Program

Selected Images

Maps

Invasive Listing Sources

• Alabama Invasive Plant Council
• Alabama Noxious Weeds - Class C Noxious Weed
• Alachua County Cogongrass Initiative
• Alberta Fisheries Act
• Alberta Weed Control Act
• Apalachicola Invasive Working Group
• California Invasive Plant Council
• City of Ann Arbor Michigan Parks and Recreation
• Colorado Noxious Weeds
• Commonwealth of Pennsylvania, Department of Conservation and Natural Resources, 1994.
• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Connecticut Noxious Weeds
• Florida Exotic Pest Plant Council - Category II
• Florida Noxious Weeds
• Georgia Exotic Pest Plant Council - Category 3
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Idaho Noxious Weeds
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Pest Species
• Indiana Prohibited Plant Species
• Invasive Plant Association of Wisconsin
• Invasive Plant Species of West Virginia
• Invasive Species of Concern in Georgia
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Maryland Aquatic Nuisance Species Plan
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Michigan’s Prohibited and Restricted Species
• Mid-Atlantic Field Guide to Aquatic Invasive Species
• Minnesota DNR invasive species list
• Montana Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• National Park Service, National Capital Region Exotic Plant Management Team Invasive Plant List
• Nevada Noxious Weeds
• New Hampshire Prohibited Aquatic Species
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• New Mexico Noxious Weeds
• New York Regulated and Prohibited Invasive Species - Prohibited
• Non-Native Invasive Plants of Arlington County, Virginia
• Non-Native Invasive Plants of the City of Alexandria, Virginia
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• North Carolina Noxious Weeds
• Ohio Invasive Species Council
• Ontario’s Invading Species Awareness Program Tracked Species List
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Pennsylvania's Field Guide to Aquatic Invasive Species
• Plant Invaders of Mid-Atlantic Natural Areas
• Rhode Island Natural History Survey
• South Carolina Illegal Aquatic Plants
• Tennessee Exotic Pest Plant Council
• Texas Noxious Weeds
• Treasure Coast Cooperative Invasive Species Mgmt. Area
• Vermont Noxious Weeds
• Virginia Invasive Plant Species List
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Invasive Species Strategic Plan and Volunteer Guidelines 2014
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References