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Eurasian watermilfoil

(Myriophyllum spicatum)

Photo of Eurasian water-milfoil
Photo credit: Alison Fox, University of Florida,

An emergent, herbaceous aquatic plant, the Eurasian watermilfoil, usually extends 3 to 10 feet but can reach as much as 33 feet in length. The stems are reddish-brown to whitish-pink. It forms dense mats on the surface of water bodies, and new plants may emerge from each node on a stem root in contact with mud. Regenerates mostly from rhizomes, fragmented stems and axillary buds that develop throughout the year. Eurasian watermilfoil can be found in nearly 400 Wisconsin lakes.

Overview map of Eurasian water-milfoil classification in WI
Restricted (orange) counties

Other names for this plant include:

  • Common names: European watermilfoil, spike watermilfoil
  • Scientific names: Myriophyllum spicatum var. muricatum

Classification in Wisconsin: Restricted

Ecological Threat
  • It invades lakes, rivers, and other water bodies ranging from fresh to brackish; it thrives in areas subjected to various kinds of natural and artificial disturbance.
  • It can form large, floating mats of vegetation on the surface of water bodies, preventing light penetration for native aquatic plants and impeding water traffic.
  • Winter-hardy, able to overwinter in frozen lakes and ponds in northern states and Canada and grow in shallow, over-heated bays such as Chassahowitzka Bay in Florida.

Leaves: Greyish-green and finely divided pairs of delicate, thin leaflets about ½-2" long; leaflets give milfoil a feathery appearance, a distinguishing feature of the plant. Arrange in whorls of 3-6 leaves about the stem.

Flowers: Small, yellow or reddish, 4-parted flowers on a spike that projects 2-4 inches above the water surface.

Fruits & seeds: A complex, segmented capsule containing four seeds.

Roots: Fibrous, often developing on plant fragments.

Similar species: Myriophyllum spicatum might be confused with several other submersed plants, including watermilfoils and underwater plants. Native northern watermilfoil (Myriophyllum sibiricum = M. exalbescens) has fewer than 12 leaf segments on each side of the leaf axis. In contrast, Eurasian watermilfoil leaves have 14 or more leaf segments on each side of the leaf axis and somewhat stouter stems than Eurasian watermilfoil. Native coontail (Ceratophyllum demersum) has leaves that are toothed and the plant feels rough when pulled through the hand, whereas Eurasian watermilfoil leaves are not toothed and the plant does not feel rough.


See the reported locations of Eurasian watermilfoil in Wisconsin.

Do you know of other populations? Please send us a report.


Chemical: Herbicides that control milfoil include 2,4-D, triclopyr, fluridone, endothall or diquat. Although in mid to late summer, plants tend to reach the surface and create a nuisance, most chemical applications for milfoil are made in the spring during the early stages of active growth. This reduces the effects on native plants. An aquatic applicator license is needed to apply chemicals in most aquatic treatments.

Manual: Hand-pulling by snorkelers or divers can be an effective removal strategy for small populations of plants. It can be used as a follow-up to chemical control to remove surviving plants. Care must be taken to remove all pieces of the plant because even small fragments can survive and re-root.

Biological: The native milfoil weevil can be stocked in lakes. The weevils feed on the plants, and the larvae burrow into the stems. They do not eat other plant types and reduce the milfoil population's vigor.

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