Eurasian Watermilfoil is a native of Asia, Europe, and northern Africa. It is a submersed aquatic plant that can reach up to 30 feet in length. It has a very feathery appearance with whorls of usually 4 leaves around the stem. Each leaf usually has 12 or more leaflet pairs which are usually very tightly spaced. As the plant reaches closer to the surface it begins to branch. The tops of the plants often turn red, and where the tip of the plant extends out of the water it produces small, reddish flowers with four petals. It spreads from stem fragments that are cut off from the original plant, as well as underground roots.
Eurasian watermilfoil is very similar to northern watermilfoil, a native, and it can be very difficult to distinguish between them. The native usually has less than 12 pairs of leaflets, does not branch at the surface, and when removed from the water its leaves remain rigid, whereas Eurasian watermilfoil goes limp.
This species can be very disruptive to an aquatic environment. It has the ability to crowed out native species and disrupt fisheries. It is also a problem for boaters as it can become entangled in the propeller which can be another dispersal method for this plant to be introduced to new waters. It is currently not known to occur in Teton County.
If you find this weed on your property or around Teton County, please report it immediately at 733-8419.