Eurasian Watermilfoil


Eurasian watermilfoil is an aquatic plant. Its stems tend to be limp, and may show a pinkish-red color. The leaves are typically divided into 12 or more pairs of threadlike leaflets. The most common native watermilfoil, northern watermilfoil, tends to have whitish or brownish stems, and leaves that divide into fewer than 10 pairs of leaflets.

How It Spreads

Eurasian watermilfoil was probably intentionally introduced to the United States. After being planted in waterbodies around the continent, its spread continued naturally as pieces of it were disseminated in flow and by motorboat traffic. Today, transport on boating equipment plays the largest role in introducing fragments to new waterbodies. It continues to spread through the aquarium and water garden trades as well.

Impacts to Rivers

Eurasian watermilfoil competes aggressively to displace and reduce the diversity of native aquatic plants, and it has less value as a food source for waterfowl than the native plants it replaces. The growth and vigor of warmwater fisheries can be harmed by the presence of dense Eurasian watermilfoil cover. Specifically, the growth of thick vegetation degrades water quality and depletes dissolved oxygen levels. Eurasian watermilfoil has also played a role in the spread of the invasive zebra and quagga mussels. Zebra mussels have been found attached to watermilfoil being transported on the trailers of recreational boaters from one waterbody to another.


River Alliance of Wisconsin Factsheet (Lower Wisconsin River Basin AIS Strategic Plan)

Wisconsin Department of Natural Resources Factsheet

Distribution in Wisconsin’s Rivers and Lakes (Wisconsin Department of Natural Resources)