Species Information

Eurasian watermilfoil Eurasian watermilfoil
RIDEM K. DeGoosh
Eurasian watermilfoil
RIDEM K. DeGoosh
Eurasian watermilfoil
Myriophyllum spicatum

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Similar Species
  • Most native watermilfoil species particularly Northern Watermilfoil (Myriophyllum sibericum)

History
  • Introduced to the United States in the 1940s

Characteristics
  • Rooted, submersed, perennial, aquatic plant
  • Narrow, whitish stems grow to the water surface, extending 3-10 ft (1-3 m) or longer
  • Forms dense beds
  • Feather-like leaves with blunt ends commonly with 12 to 24 pairs of leaflets on each leaf
  • Leaves are grouped in whorls of 3 - 6 leaves around stem
  • Small flowers project 2-4 in (5-10 cm) above the water surface

Habitat
  • Lakes, ponds, slow-moving streams, reservoirs, and estuaries
  • Depths greater than 3 ft (0.9 m)
  • Tolerates brackish water
  • Thrives in highly disturbed lake beds, lakes receiving nitrogen and phosphorus-laden runoff, and heavily used lakes

Known Distribution in the Northeast
  • Quebec and most of the U.S. 
  • Native to Europe and Asia

Impacts
  • Highly aggressive, nuisance species
  • Can form dense mats that shade and crowd out native plants
  • Degrades habitats used by fish for spawning and feeding
  • Thick growth can impair recreational uses of waterways including boating, swimming, and fishing
  • Yellow-green, matted vegetation on milfoil-dominated lakes creates perception that lake is “infested” or “dead"
  • Control efforts cost millions of dollars annually; $500,000 per year in New York state alone

Eurasian watermilfoil underwater
Eurasian watermilfoil leaves
MEDEP-K.Hahnel
Eurasian watermilfoil
RIDEM - K.DeGoosh
Eurasian watermilfoil (Myriophyllum spicatum)
Alison Fox, University of Florida
Eurasian watermilfoil-leaves whorled around stem
MEDEP - K.Hahnel