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Eurasian Watermilfoil

Myriophyllum spicatum

Eurasian watermilfoil's feathery leaves lose their shape when taken out of water. (Maryland Department of Natural Resources)
Eurasian watermilfoil's feathery leaves lose their shape when taken out of water. (Maryland Department of Natural Resources)

Eurasian watermilfoil is a bay grass with whorls of feathery leaves along long, branching stems. It grows in quiet fresh and slightly brackish waters throughout the Chesapeake Bay watershed.

Appearance:

  • Tough, branching stems that can grow to 8 feet long
  • Delicate, feather-like leaves that grow in whorls of 4-5 along each stem
  • Leaves lose their shape when taken out of the water
  • Spikes of reddish flowers that poke above the water’s surface in late summer
  • Rooted base

Habitat:

  • Common in slow-moving or protected fresh and slightly brackish waters
  • Cannot tolerate strong waves or currents
  • Often grows in sandy mud

Range:

  • Found in the upper Chesapeake Bay from the Susquehanna Flats to just north of the Chesapeake Bay Bridge
  • Also grows in tributaries throughout the Bay watershed, from fresh non-tidal streams to slightly brackish tidal rivers
  • Native to Europe and Asia

Reproduction and Life Cycle:

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

Other Facts:

  • Provides good habitat for young fish, crabs and invertebrates
  • 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.
  • 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:

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