Eurasian Watermilfoil


Eurasian watermilfoil (Myriophyllum spicatum) is a common aquative invasive plant that is widely distributed across New York State. It is a submersed aquatic plant identified by long stems with feather-like leaves arranged in whorls of four around the stem. Each leaf is finely divided into 9 to 21 pairs of leaflets. Leaves are limp when removed from the water. Each stem usually branches several times as it reaches the water surface, forming a dense floating mat. The stems often turn red, especially towards the top of the plant. Spikes with small, reddish flowers rise above the water surface. Eurasian watermilfoil can reproduce through seeds, but it most often spreads by vegetative fragmentation. The native northern watermilfoil, with which it can be confused, usually has 5 to 9 pairs of leaflets, and the leaves are rigid out of water.


Eurasian watermilfoil is native to Europe, Asia, and northern Africa. It was introduced into North America in the 1940's and has spread to 48 states and three Canadian provinces. The rapid spread of Eurasian watermilfoil across North America has been attributed mainly to boat traffic; plant fragments were accidentally transported from one lake to another on boats and trailers. Eurasian watermilfoil is the most common and widely distributed aquatic invasive plant in New York State. It can be found in all watersheds, although still relatively rare on Long Island. There are multiple occurences of eurasian watermilfoil across the Adirondack Park. 


Eurasian watermilfoil is highly invasive and competes aggressively with native aquatic plants, thereby reducing diversity. A single fragment of stem or leaves can take root and form a new colony, and plants can grow up to 2 inches per day. Eurasian watermilfoil can grow in many types of waterbodies, as well as on almost any substrate. Since its growth is typically dense, Eurasian watermilfoil beds are poor fish spawning areas, and excessive cover may lead to populations of stunted fish. Dense surface mats can interfere with boating, fishing, swimming, and other forms of water recreation. It can also lower the value of lakefront property.


Information complied from:

Iowa Department of Natural Resources , (2005). Eurasian watermilfoil fact sheet
NYS Department of Environmental Consercation, (2014). Common aqautic invasive species of NY

Additional Information on Eurasian Watermilfoil
Iowa Department of Natural Resources May 27, 2014
Fact sheet on Eurasian Watermilfoil.
Lake George Association May 27, 2014
A comparison between EWM and native northern milfoil.
Lake George Association May 27, 2014
Information on aquatic plant species commonly confused with Eurasian Watermilfoil.
Eurasian Watermilfoil
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