Eurasian watermilfoil

Дата канвертавання24.04.2016
Памер10.83 Kb.


(Myriophyllum spicatum)

  • E
    urasian watermilfoil is a submersed, perennial, aquatic plant.

  • The leaves are arranged in groups of 4 (or occasionally 5) around the stem.

  • The feather-like leaves usually have 12 or more pairs of leaflets.

  • The tiny pink flowers, on reddish spikes, stand out of the water but submerse after pollination.


The native aquatic buttercup (Ranunculus aquatilis) is often mistaken for Eurasian watermilfoil. Its underwater leaves are thread-like, but the leaflets occur in bunches, not in a feather-like configuration. The flowers are white.

Northern watermilfoil (Myriophyllum sibericum), is shown on the left in the picture, with Eurasian water milfoil on the right. Northern watermilfoil leaves have fewer pairs of leaflets.
There are other native milfoils and identification can be very difficult. For more information see


An early infestation of Eurasian watermilfoil was found in Lake Sutherland in the summer of 2000, and there are small amounts in several ponds in the county.


Eurasian watermilfoil forms dense surface mats that can:

Control of Eurasian watermilfoil costs the State of Washington $1,000,000 per year.
Eurasian watermilfoil is a Class B designate weed.

Control is required in Clallam County.


  • Eurasian watermilfoil is normally a submersed, aquatic plant, rooted in the substrate. However, if water evaporates slowly and plants become stranded, it can develop a land form.

  • Seeds rarely produce seedlings and are not a common means of reproduction.
  • Reproduction occurs when plant fragments break off automatically in the fall or are broken off by human activity. Fragments often develop roots before separating from the parent plant, and a small piece of stem or root can grow into a whole new plant. Fragments are often carried on boats or trailers and moved between water bodies.

Prevention and early detection are the best means of control!

  • Clean boats and trailers thoroughly when moving between water bodies.

  • Monitor water bodies frequently; look for floating fragments as well as rooted plants.

  • Bring in all suspicious-looking plants for positive ID


COVERING milfoil with an opaque fabric, such as burlap, can effectively control small populations.
HANDPULLING (similar to pulling weeds out of a garden) can be used as a control measure where possible. Always collect and dispose of plant fragments.
RAKING with a rake attached to a rope may reduce plant density, but will probably not remove the root mass. This method is not allowed in certain lakes, because of potential impact to sockeye spawning areas. Carefully gather and remove any plant fragments created.

LOWERING the water level can desiccate plants in dry climates, or kill them if temperatures fall below freezing for a prolonged period of time.
CUTTING, HARVESTING AND UNDERWATER ROTOTILLING, can create open areas of water. However, each of these methods creates fragments which may increase the spread of milfoil. Washington state law requires that cut plants be removed from the water.

  • Several insects are being tested for use in controlling Eurasian water milfoil.

  • Research is underway on plant pathogens that will control Eurasian watermilfoil.

  • Triploid grass carp will eat Eurasian water milfoil, but may prefer other vegetation.

HERBICIDE applications near or over water require a specially licensed applicator and a permit from the Departments of Ecology or Agriculture; a permit may not be required for ponds that are smaller than one acre and are completely enclosed with no outlet to other water bodies.

Call if you see this plant!
Prepared by the Clallam County Noxious Weed Control Board; revised 12/2000

For more information call: (360) 417-2442

or see

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