Eurasian watermilfoil
Myriophyllum spicatum
Description
A perennial aquatic plant with purplish red branching stems that grow up to five feet long. It is very similar to the native northern watermilfoil (Myriophyllum sibericum), and can be distinguished by the following characteristics:- It usually has twelve or more leaflet pairs on each leaf.
- Its leaves tend to collapse around the stem when removed from the water. Other milfoil species have thicker stems and are usually more robust.
- The mature leaves are typically arranged in whorls of four around the stem.
Habitat
Lakes, ponds, shallow reservoirs and low energy areas of rivers and streams. Brackish water of protected tidal creeks and bays. Particularly troublesome in water bodies that have experienced disturbances such as nutrient loading, intense plant management, or abundant motorboat use.Distribution
Common throughout western Oregon and the Columbia Basin; southwestern Idaho; the Columbia, Okanogan, Snake, and Pend Oreille Rivers and in many nearby lakes in Washington, closely follows the I-5 corridor in western WashingtonImpacts
Inhibits water flow in waterways, reduces water quality of freshwater habitats, impedes recreation, adverse impact to fish populationsDispersal Methods
Plant fragmentation due to wind, wave action, and boat activityPrevention
Look for this weed particularly in water bodies that have experienced disturbances such as nutrient loading, intense plant management, or abundant motorboat use. Most identifiable by the high number of leave pairs, the four leaf whorls, and if the leaves collapse around the stem when removed from the water.Listings
ODA's B ListFactsheets
Western Aquatic Plant Management Society Fact Sheet
Photos
Distribution Map
Distribution in Oregon
Distribution in Washington
Other Links
Foiling Watermilfoil by Marcia Wood - Article from the USDA Agriculture Research Service Website
Idaho Department of Agriculture Eurasian Watermilfoil Control Program