Eurasian Water-Milfoil

  • Eurasian Water-Milfoil

    (Myriophyllum spicatum)

    Eurasian Water-milfoil is an invasive aquatic plant native to Europe, Asia, and northern Africa. It was introduced to North America in the 19th century, and is now widely distributed throughout the continent.


    Eurasian Water-milfoil was first detected in Canada in Lake Erie in 1961. It now inhabits all of the Great Lakes, as well as many inland lakes throughout southern and central Ontario. It can now be found on every continent except Antarctica.

    Alison Fox, University of Florida,

    Alison Fox, University of Florida,


    Graves Lovell, Alabama Department of Conservation and Natural Resources,

    Leslie J. Mehrhoff, University of Connecticut,

    Leslie J. Mehrhoff, University of Connecticut,

  • Identification

    • The plant is a perennial that grows under the water surface.
    • Feathery green leaves circle the stem in groups of four or five.
    • Leaves have 12 or more thread-like segments (the native Northern Water-milfoil has 11 or fewer leaf segments).
    • Tiny, reddish flowers grow on spikes five to 20 cm long that rise above the water.
    • This plant blooms in late July and early August.


    • This plant aggressively out-competes native species, resulting in lower biodiversity.
    • Reduced oxygen in water caused by decomposing plants can kill fish.
    • Thick mats of Eurasian Water-milfoil can make certain recreational activities such as boating, fishing, and swimming quite difficult.
    • Dense stands can create stagnant water, which is ideal habitat for mosquitoes.

    Help Stop the Spread

    • Learn how to identify Eurasian water-milfoil and distinguish it from beneficial native species.
    • Avoid infested areas or reduce your sped when travelling near Eurasian Water-milfoil beds. Your propeller can break off fragments, which can form completely new plants in non-infested areas.
    • Thoroughly inspect your boat, trailer, and equipment after each use. Remove any plants, animals, or mud before moving to a new water body.
    • Avoid planting Eurasian Water-milfoil in aquariums and water gardens. Try using only native or non-invasive plants in your aquariums.
    • Never release unwanted aquarium plants or pets. Return or donate them to your local pet store, or put them in the garbage. Do not compost or discard the plant in natural areas, as they may still be capable of producing seeds that can sprout.
    Ontario Invaders Species Account PDF
    Leslie J. Mehrhoff, University of Connecticut,

    Leslie J. Mehrhoff, University of Connecticut,