Eurasian Watermilfoil

How to identify it

Size: Leaves about 1/2 to 2 inches long, on long stems that can reach the surface.

• Soft, feathery leaves in rings (whorls), usually four to a ring, around the stem.
• 12 or more pairs of thread-like leaflets on each leaf. Count them: this is the most useful check.
• Leaf tips that often look blunt, as if clipped off.
• Reddish stem tips, often branching near the surface.

Don’t confuse it with

Native northern watermilfoil usually has fewer leaflet pairs, about 5 to 10, and stiffer leaves. The two can also cross, and the hybrid can be hard to tell apart without a lab test.

Where it came from

Native to Europe, Asia and northern Africa.

Established in North America by the mid-1900s. It spreads between lakes mainly as plant pieces caught on boats, trailers, motors and fishing gear. A single piece can start a new plant.

Earliest dated Michigan record: 1961, Harsens Island, St. Clair County. This is the oldest dated record in the USGS non-native species database, not necessarily when it first arrived.

Why it matters

It can form thick mats at the surface that crowd out native plants, make swimming and boating difficult, and change the habitat fish use.

Michigan law

Restricted under Part 413 of Michigan's Natural Resources and Environmental Protection Act. It is illegal to possess, introduce, import, sell or offer to sell it as a live organism, except in the limited cases the law allows. The state uses “restricted” for species already established in Michigan. The state’s page on this species.

Michigan lakes where it has been recorded

122 Michigan lakes on this site have a record of this species.

A lake that is not listed may still have it. Records exist only where someone found the species and reported it, so “not recorded” does not mean “not present.”

Lake records: Midwest Glacial Lakes Partnership Conservation Planner; underlying records from the USGS Nonindigenous Aquatic Species database.