Eurasian watermilfoil

Eurasian watermilfoil can out shade native plants and reduce water oxygen levels.

Place of origin

Originally from Eurasia and North Africa, Eurasian watermilfoil (Myriophyllum spicatum) was introduced to North America in 1961 in Lake Erie, Ontario. To our knowledge, Eurasian watermilfoil is currently not present in Alberta.


Prefers shallow water but can root up to 10 m in depth.


  • Perennial, submersed; flowers are very small, reddish and held above water on a flower spike.
  • Usually 12 to 21 closely spaced leaflet pairs per leaf.
  • Feather-like leaves collapse around stem when out of water.


  • A single segment of stem and leaves can form a new colony.
  • Plant does produce seeds but germination rates are usually poor.
  • Stem fragmentation and underground runners allow this plant to reproduce rapidly.


  • Forms large, floating mats that prevent light penetration into waterbodies, out-shading native plants and reducing oxygen levels when decomposing.
  • Out-competes native milfoils.


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