Eurasian watermilfoil (Myriophyllum spicatum)


(Picture courtesy of Debbie Bowen)
Scientific Name:
Myriophyllum spicatum, (Eurasian water milfoil) (1)

Description:  Perennial. The weed is usually found under water.  This plant was introduced to North America in the 1940's.  (2, 4)

Leaves:  Usually has 9 to 21 leaflets.  Leaves will grow up to 2.54 cm long and are very fine and needle like.  Leaves also become rigid when they are out of water whereas they are like feathers when they are in the water.  The leaves are usually divided into 9 leaflets, and the end of the leaves has a blunt tip.  Some leaves may grow in a  twirl pattern around the stem.  When the leaves are taken out of the water they lose their stability and collapse  around the stem. (2, 3, 6)

: Stout, slender, and roots extend from the stem in many places. Stems can be 3 meters or longer in length. The stems are able to produce new plants by fragmentation (breaking off).  The stem is usually pale pink to red to reddish brown and has feathery leaves. (2, 3)

:  The flowers of this weed radiate from the swirling leaves and form closely to the leaves.  The growing tips at the end of the plant are bright red or pink color.  The flower is in a spike form and has small, yellow four petaled flowers in clusters on the end of it. The spike is usually twice as wide as the stem.  The spike on the flower is about 5-20 cm long.  The flowers are above the water. (2, 3, 6)

:  The roots are fibrous, and are at the base of the plant and on the segments of the stem. (2, 7)

:  The plant spreads and reproduces by fragmentation, which is asexual, and also by sexual reproduction (flowers, fruit and seeds). (2)

:  The seeds are usually about 2-3 mm long and come in bunches off of the weed. (3, 2)

Fruit: Small segmented capsule that has fours seed inside of it. (7)

Habitat and Range
:  Eurasian water milfoil is an aquatic weed.  This weed is generally found near the surface or just below it. It grows best in fine grained inorganic sediments (4, 6).

Prevention: Some ways to keep Eurasion water milfoil from spreading to other bodies of water is to  check all the equipment (boats, motors, trailers, fishing gear, ect.) that was used in infested waters and remove all aquatic plants when leaving the lake or river. Plants can be hand pulled to get rid of really thick areas of the weed.  This, however is not very effective for long term solution because fragments of the plant could be left behind. Mechanical harvesters can also be used to get rid of very large infestations, but like hand pulling its not an effective long term solution. (6)

Herbicides: Some herbicides can be used on this plant (in water).  Check with your local weed coordinator or extension agent and read the label on the herbicide. 

Biological Control: The only known biological control so far is the weevil  Eurhychiopsis lecontei. The adult weevils eat Eurasion water milfoil and the female weevils lay eggs on the top of the weed, and when the eggs hatch the larvae burrow holes throughout the stem of the plant, casuing a lot of damage. (6)

Notes: Eurasian water milfoil has now (2008) invaded Montana in the Clark Fork River, near Noxon.  [Breitenfeldt, Todd].

1. Debbie Bowen. "Eurasian water milfoil: fact sheet." MNSG. Feb. 11, 2004. Minnesota Sea Grant. 3/10/04,

2. "Plant Identification." Adirondack Park Invasive Plant Program. . Aquatic Invasive Plant Project. 3/19/04,

3. "Eurasian Water milfoil: Myriophyllum spicatum." Virginia Tech Weed Identification. . . 3/10/04,

4. Colette Jacono. "Eurasian water milfoil." . 3/16/04. . 3/19/04,

5. "Minnesota DNR." Eurasian water milfoil. . . 3/18/04,

6. "Eurasion Water Milfoil (Myriophyllum spicatum)." Wisconsin Department of Natural Resources. 2/23/09, []

7. "Eurasion Water Milfoil." Montana Noxious Weed. 2/23/09, []

By: Zac and Layne.   Updated By: Travis Sizemore, 2/8/05.   Updated By: Megan Enriquez, 2/25/09

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