Department Header For Noxious Weed Division
Yellowstone County, Montana
Noxious Weed
Weed Information Contact Department

Eurasian Watermilfoil
(Myriophyllum spicatum)

Eurasian Watermilfoil

Photo from Montana's Noxious Weeds, revised ed.
by Monica Pokorny & Roger Sheley.

Used with permission from
Montana State University Extension.

Eurasian Watermilfoil Aquatic

Eurasian Watermilfoil Stem

Eurasian Watermilfoil Leaf

Eurasian Watermilfoil Bloom

Eurasian Watermilfoil Mature 1

Eurasian Watermilfoil Mature 2

Growth Habit: submerged herbaceous perennial herb native to Europe, Asia, and northern Africa. Accidentally introduced to the United States in the late 1800's.

Leaves: Three to four bright green leaves are whorled around the stem at each joint. Each leaf is 1.2 inches in length and has 12 to 48 thread - like divisions. Leaves rarely extend above the water surface.

Stem: Stems can be 10 feet or more in length and 0.1 inches thick.

Flower: A rigid pink flowering spike, from 2 to 8 inches long, is held erect above the water surface from June to August. Small yellow four-petaled flowers are arranged in clusters on the flowering spike.

Roots: Eurasian Water Milfoil has numerous roots at the base of the plant and along the stem.

Seeds: Hard, segmented capsule containing four seeds.

Reproduction: Asexual reproduction via sprouting plant fragments and rhizomes is the dominant means of spread.

Habitat: lakes, ponds, slow moving streams, reservoirs, estuaries and canals

Biological Control:

Herbicides: Sonar AS