Native Range

Europe, Asia and northern Africa

Appearance

Eurasian watermilfoil is a submersed aquatic perennial with roots often anchored in the hydrosoil. Plant stems are reddish-brown to light green, up to 20 ft (6 m) long, and become more branched near the water’s surface. Leaves occur in whorls of four, are 1–1.5 in (2.5–3.8 cm) long, and are feather-like with 12–24 pairs of filament leaflets. Tiny pink flowers are produced on pink emergent spikes up to 6 in (15 cm) long. Fruits are 4-chambered spheres; each chamber produces one rough-textured seed.

Impact

Eurasian watermilfoil displaces native plant species and decreases the abundance and diversity of aquatic insects and fish. Decaying plant material can decrease oxygen levels, which is a further detriment to fish and other organisms. Large infestations impede water flow and can cause stagnant water conditions that create habitat for mosquitoes and the parasites that cause swimmer’s itch. Large infestations also damage fishing, hunting, boating, and other recreational activities. Eurasian watermilfoil is capable of hybridizing with the native northern watermilfoil (Myriophyllum sibiricum), and some hybrid strains have proven to be even more aggressive.

Reference

Andreas, J.E., W.J. Glisson, B. Muffley, and J.K. Parsons. 2024. Eurasian Watermilfoil (Myriophyllum spicatum): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2024-3-EURASIAN WATERMILFOIL-P. https://bugwoodcloud.org/resource/files/33588.pdf

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
• Delaware Invasive Species Council
• Florida Invasive Plant Council - Plant List - 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 EDRR
• Nevada Noxious Weeds
• New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture,  Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
• 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 Noxious Weeds
• 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
• South Carolina Invasive Pest Council
• South Carolina Plant Pest List
• Tennessee Exotic Pest Plant Council
• Texas Noxious Weeds
• Treasure Coast Cooperative Invasive Species Mgmt. Area
• Utah Noxious Weeds
• 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