Eurasian watermilfoil (Myriophyllum spicatum)

Eurasian watermilfoil Common Names: Spiked watermilfoil

Description: This species is listed as a restricted noxious weed by the Michigan Department of Agriculture. Eurasian milfoil begins to photosynthesize and grow prolifically in early spring, allowing it to dominate an area and limit light available to other aquatic life.

Habit: Submergent aquatic perennial, commonly ranges from 1-3 m (3-10 ft) in length but may reach 4 m (33 ft), forms dense mats.

Leaves: Submerged, feather-like, 4-5 leaves with 9-21 threadlike pairs of leaflets whorled around stem at each node, bright green in color, limp when out of water.

Stems: Thick near the base, becoming more slender and branching near the water surface; usually 1-3 m (3-10 ft) long.

Flowers: Inconspicuous, yellow in color, 4-parted, flower spikes rise 5-10 cm (2-4 in) above water surface.

Fruit and seeds: Seed pod that contains 4 seeds.

Habitat: Found throughout Midwestern ponds and lakes in 1-3.5 m (3-12 ft) of water, prefers disturbed shorelines and nutrient rich waters.

Reproduction: Vegetatively by fragmentation and creeping runners; seeds viable but not an important dispersal mechanism; unlike many aquatic plants, it does not produce turions.

Similar species: Although many aquatic plants look similar superficially, Eurasian water milfoil is unique in having whorled, pinnately compound leaves with 12-20 leaflets on each side. It most closely resembles northern water milfoil (Myriophyllum exalbescens), which has only 7-11 pairs of leaflets, remains rigid out of water and forms winter buds.

Monitoring and rapid response: Monitor water bodies for new colonies. Public education and prevention is critical. Reduce nutrient enrichment where possible; hand pull or rake out colonies, removing all fragments; biological control with native herbivorous weevil (Euhrychiopsis lecontei) shows promise; herbicides show mixed results; check current research -treatment rapidly evolving. Permits are usually required for herbicide use in water bodies and wetlands. For information see MDEQs Aquatic Nuisance Control website at: www.michigan.gov/deqinlandlakes.

Credits: The Michigan Natural Features Inventory (MNFI) has partnered with MISIN to provide the information in this fact sheet. Species images and/or information were used with permission from "A Field Identification Guide to Invasive Plants in Michigan's Natural Communities" and "A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan.


Common Name:

Eurasian watermilfoil

Scientific Name:

Myriophyllum spicatum

Family:

Haloragaceae
(Water milfoil)

Duration:

Perennial

Habit:

Aquatics

USDA Symbol:

MYSP2