Eurasian Water Milfoil

This submerged aquatic plant is native to Eurasia and northern Africa.  It has the ability to stay alive over winter and grow rapidly in the spring, blocking out sunlight needed by native plants.  It keeps out larger fish and impairs the ability of some fish to spawn.

Habitat

Occupies water 3 – 12’ deep, growing best in fertile, fine texture, inorganic sediments.  Prefers highly disturbed lake beds, heavily used lakes and lakes receiving nitrogen- and phosphorus-laden runoff.  Also found in ponds, slow moving streams, reservoirs, and estuaries.   It is not successful in undisturbed areas where native plants are well established.

Leaves:  Submerged, feathery, limb when out of water, 4 – 5 leaves whorl around the stem at each node.  Typically uniform in diameter, consists of 9 – 21 thread like pairs of leaflets that resemble bones on a fish spine.
Flowers:  Tiny, inconspicuous, and located in the axils of flower bracts, either four petals or without.  Flower spike rises 2 – 4” above the water surface.
Fruit:  Four jointed nut-like bodies.
Stem:  Slender, thickened below the flower, doubles in width further down, becomes leafless near the base. Usually 3 -10’ long but can reach 33’ in length.  Often branch repeatedly at the waters surface.
Reproduction:  Primarily by fragmentation due to boating and wave action.  Fragments stay alive for weeks if kept moist.  They also reproduce by runners.
Control:  Hand-pulling is the best method.  Raking is also an option. All plant fragments must be removed from the water and shoreline.  Manipulating the water level may help if that is possible to do.  2,4-D and Fluridone are the most commonly used chemicals used against this species.  However, both of these have mixed results and can affect native plant populations.  Researchers have found a native North American weevil that feeds on Eurasian Water-milfoil, but this method also has mixed results.

This submerged aquatic plant is native to Eurasia and northern Africa.  It has the ability to stay alive over winter and grow rapidly in the spring, blocking out sunlight needed by native plants.

Impacts

It keeps out larger fish and impairs the ability of some fish to spawn.

Identification

Habitat:  Occupies water 3 – 12’ deep, growing best in fertile, fine texture, inorganic sediments.  Prefers highly disturbed lake beds, heavily used lakes and lakes receiving nitrogen- and phosphorus-laden runoff.  Also found in ponds, slow moving streams, reservoirs, and estuaries.   It is not successful in undisturbed areas where native plants are well established.

Leaves:  Submerged, feathery, limb when out of water, 4 – 5 leaves whorl around the stem at each node.  Typically uniform in diameter, consists of 9 – 21 thread like pairs of leaflets that resemble bones on a fish spine.

Flowers:  Tiny, inconspicuous, and located in the axils of flower bracts, either four petals or without.  Flower spike rises 2 – 4” above the water surface.

Fruit:  Four jointed nut-like bodies.

Stem:  Slender, thickened below the flower, doubles in width further down, becomes leafless near the base. Usually 3 -10’ long but can reach 33’ in length.  Often branch repeatedly at the waters surface.

Reproduction:  Primarily by fragmentation due to boating and wave action.  Fragments stay alive for weeks if kept moist.  They also reproduce by runners.

Control/Management

Hand-pulling is the best method.  Raking is also an option. All plant fragments must be removed from the water and shoreline.  Manipulating the water level may help if that is possible to do. 2,4-D and Fluridone are the most commonly used chemicals used against this species.  However, both of these have mixed results and can affect native plant populations.

Biological control: Researchers have found a native North American weevil that feeds on Eurasian Water-milfoil, but this method also has mixed results.

For more information:

  • Water milfoil

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    Black & Pale Swallow-worts |   Giant Hogweed |  Purple Loosestrife |  Water Chestnut | Glossy Buckthorn |  Eurasian Water Milfoil |  Rock Snot, Didymo | European Frogbit | Japanese Knotweed