Quick Facts

Species Type

Nonnative

Size

Stems can grow to 8 feet in length

Habitat

Slow-moving or protected fresh and slightly brackish waters; cannot tolerate strong waves or currents

Range

Native to Europe and Asia; found in the upper Chesapeake Bay from the Susquehanna Flats to just north of the Chesapeake Bay Bridge. Grows in tributaries throughout the Bay watershed, from fresh non-tidal streams to slightly brackish tidal rivers.

Conservation Status

Stable

Appearance

The Eurasian watermilfoil is made up of tough, branching stems that can grow to 8 feet long. They have delicate, feather-like leaves that grow in whorls of 4 to 5 along each stem. Leaves lose their shape when taken out of the water. Spikes of reddish flowers poke above the water’s surface in late summer. The plant has a rooted base.

Reproduction and Life Cycle

This grass usually reproduces asexually when stem fragments form into new plants. It can also reproduce sexually in late summer, when female flowers are pollinated through the air. They produce nut-like seeds that sink to the bottom. Seeds can remain viable for years.

Did You Know?

  • Eurasian watermilfoil provides good habitat for young fish, crabs and invertebrates.
  • This plant was accidentally introduced in the Chesapeake Bay in the early 20th century. By the late 1950s, thick mats of Eurasian watermilfoil covered thousands of acres of the Bay and its rivers. By 1970 these large beds died back, and today the species grows in moderation.
  • It can be confused with coontail. You can distinguish Eurasian watermilfoil by its feathery leaves that lose their shape when taken out of the water.

Sources and Additional Information