Invasive Species (Aquatic) -


Eurasian watermilfoil
(Myriophyllum spicatum L.)

Photos & Description courtesy of IPANE

Where it's from

Asia or North Africa


What Eurasian watermilfoil does to the habitat

Eurasian Watermilfoil can root in water as deep as 30 feet. The shoots come up to the surface and multiply to form a mat along the top of the water that makes swimming, boating and fishing impossible.


It crowds out light for plants and animals and changes the chemistry of the water by adding more phosphorus and more nitrogen.


When winter kills the tops above the water line, the decaying vegetable matter deprives the water of so much oxygen that it often leads to fish kills.



You need to be careful to avoid breakage as that can easily spread the problem. Small areas can be cleaned up with a pond rake. There are machines that will capture large areas, but with this technique you have to be especially careful of not spreading it.


Additives to the water that filter out light work in some areas, but that effects all plants, not just the targets.


The same is true of herbicides. What works will kill both native and invasive species.


Common Name

Full Scientific Name

Eurasian watermilfoil
spiked watermilfoil

Myriophyllum spicatum L.

Family Name Common

Family Scientific Name

Watermilfoil family Myriophyllum spicatum


Botanical Glossary

Myriophyllum spicatum is a submerged, aquatic perennial that can have green, reddish-brown or whitish pink stems 1.8-6 m (6-20 ft.) long. The leaves are olive green in color, and less than 5 cm (2 in.) long. They are soft and feather-like in texture, and each mature submerged leaf has a central midrib with 12-20 filiform segments on each side. There are both male and female flowers on the same inflorescence. The female flowers are basal while the male flowers are located distally. The female flowers have a 4-lobed pistil and lack sepals and petals. The male flowers have 4 pink petals and 8 stamens. The globular fruit are indehiscent, 2-3 mm (0.08-0.11 in.) long and contain 4 seeds. Page References Crow & Hellquist 194, Fernald 1073, Gleason & Cronquist 308, Holmgren 290, Magee & Ahles 772.

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