What is Eurasian Milfoil?

Eurasian water-milfoil

Eurasian Water-milfoil is commonly called Eurasian Milfoil, and for brevity is frequently referred to as simply milfoil on this website. It's botanical name is Myriophyllum spicatum. It is a submersed aquatic plant native to Europe, Asia, and northern Africa. The plant was introduced to the United States around 1940, and has spread throughout much of North America.

Generally found in water 3 to 10 feet deep, milfoil reproduces extremely rapidly, and can infest an entire lake within two years of introduction by forming thick underwater beds of tangled stems and a vast canopy mat of vegetation at the water's surface.

The plant can take over a lake rapidly due to it's ability to store more nutrients in it's roots than native plants. This results in it being able to sprout early in the spring, allowing it to block the sunlight needed by other plants to sprout.

Identifying Eurasian Milfoil

Northern vs. Eurasian Milfoil

Northern Milfoil            Eurasian Milfoil

Eurasian milfoil has slender stems encircled by feathery leaves in groups. It can be difficult to identify for the casual observer because you are typically looking down at the plant in the water, and if you break off a stem to get a better look it appears quite different from it's appearance in the water.

The photograph above is a good representation of how it would appear in the water if you were observing it wearing a diving mask. The right-most plant in the photograph at the right shows what it looks like when removed from the water

Northern milfoil, which is a native, non-envasive plant, closely resembles Eurasian milfoil, and can also be found in Brant Lake. It can be distinguished by the number of leaf divisions; Eurasian milfoil has 9-21 pairs of leaflets per leaf, while Northern milfoil typically has 7-11 pairs of leaflets. Another technique for telling the two apart is that the feathery leaves of Eurasian milfoil collapse when removed from the water, while Northern Milfoil leaves remain firm. The photograph on the right illustrates this difference.

How Eurasian Milfoil Spreads

Milfoil propigating

Milfoil is introduced to a body of water by stem segments that are transported from another infected body by boats, trailers, bilges, live wells, or bait buckets, where they can stay alive for weeks if kept moist. Waterfowl may also play a part.

Although milfoil produces many seeds, it's seeds germinate poorly, and most increase and spread of the species is the result of fragmentation. In the late summer and fall the plants become brittle and naturally break apart. These fragments can float to other areas, sink, and start new plants. Once a plant is established in a new area, it spreads locally from runners that creep along the lake bed. Milfoil reproduces extremely rapidly and can infest an entire lake within two years of introduction.

Captured! An Eurasian Milfoil fragment
looking for a new home in Brant Lake

This milfoil fragment was removed from the lake in September 2008 during a mat laying effort.

It was one of many, floating near the surface, being carried by the current at a moderate pace on a quest for a hospitable environment to establish a new milfoil colony; perhaps just off your beach.

This is a mean, green, reproduction machine! We have a formidable foe.