Scientific name: Myriophyllum spicatum

What Is It?

Eurasian watermilfoil is a submersed plant that grows in a variety of still and flowing freshwater bodies. It can tolerate a range of salinity, acidity, and temperature. Watermilfoil forms dense mats that shade native aquatic plants, inhibit water flow, and hamper recreation

Is It Here Yet?

Yes. Eurasian watermilfoil has been documented throughout Washington.

Why Should I Care?

Eurasian watermilfoil forms dense mats on the water surface, interfering with recreational activities, displacing native vegetation, causing flooding, and clogging water intakes. It can infest an entire lake quickly, and provides poor habitat and a low-quality food source. Mats of vegetation provide good mosquito habitat. Eurasian watermilfoil’s ability to hybridize with native northern milfoil threatens the survival of our native milfoil species.

How Can We Stop It?

Clean your boat and any other equipment or gear that has entered potentially infested waters. Eurasian watermilfoil is on Washington’s Wetlands and Aquatics Quarantine list, meaning it is prohibited to transport, buy, sell, offer for sale, or distribute Eurasian watermilfoil plants or plant parts. Eurasian watermilfoil also is listed as a Class B Noxious Weed in Washington, meaning it is designated for control in certain state regions.

What Are Its Characteristics?

  • Plant roots on the bottom of a water body and mainly grows underwater.
  • Leaves grow in sets of four (or, rarely, five) arranged around a stem.
  • Reddish flower spikes emerge a few inches above the water with small pinkish flowers and one short leaf below each flower.

How Do I Distinguish It From Native Species?

Eurasian watermilfoil may be distinguished from native milfoils by the arrangement of its 1 inch- to 1 1/2-inch-long leaves in whorls of four around stems that are reddish or green in summer. It typically has more leaflet pairs per leaf (14-21) than native milfoils. The plant also may be confused with the invasive parrotfeather.

Additional Photographs