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Class B Noxious Weed

Parrotfeather
Myriophyllum aquaticum
 

Parrotfeather close up


Plant family: Haloragaceae
Year listed: 1994
Native to: The Amazon river, South America.

Why is it a noxious weed?
Parrotfeather is another ornamental aquatic plant that has escaped cultivation. Infestations can alter aquatic ecosystems. It forms dense mats that shade out other native aquatic plants, inhibits water flow, and recreational activities.

 

How would I identify it?
General Description: Submerged aquatic plant. Has emergent and submersed leaves. Long, intertwined rhizomes intertwine to form a dense mat.

Leaves:

  • feather like
  • arranged in whorls
  • emergent leaves bright green
  • emergent leaves look similar to little fir trees
  • submersed leaves darker

Flowers:

  • inconspicuous, white

Stems:

  • emergent stems can grow up to a foot out of the water

How does it reproduce?
Since only female plants are present in North America parrotfeather reproduces by stem/rhizome fragments.

Where does it grow?
Parrotfeather is found in freshwater ponds, streams, lakes and canals.

What is the distribution in Washington State?

 

 

 

Click on map to enlarge.
  • Parrotfeather has been documented in Island, Snohomish, King, Pierce, Thurston, Lewis, Yakima, Skamania, Clark, Cowlitz Wahkiakum, Pacific, Grays Harbor and Clallum counties.
  • If you think you may have seen this weed, please contact your county weed coordinator or us at noxiousweeds@agr.wa.gov.

 

  • Distribution map is based on 2003 data.

How do I control it?

General control methods: Parrotfeather can be difficult to control. Since it spreads by stem/rhizome fragments, mechanical methods such as cutting, harvesting and underwater tilling is not advisable. These methods can increase infestation.

Cultural: Not effective.

Herbicide: Because herbicide availability and regulation differ between States, as well as between countries, we recommend the Washington Department of Ecology web site for information on aquatic weed management and herbicides.

Mechanical: Not advised unless area is entirely invaded by plants. Otherwise, mechanical methods may increase infestation.

Biological: Parrotfeather is unpalatable to grass carp.

Are there plants that may be confused with Parrotfeather?
Parrotfeather looks similar to Eurasian watermilfoil (Myriophyllum spicatum), also a Class C noxious weed in Washington. If you need help with identification, please contact your county weed coordinator.

For more information
For more information, download our Written Findings.

View the Garden Wise Eastern Washington and Western Washington Guides for better noninvasive plant recommendations for your yard or garden.

More Photos-Click photo to enlarge
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Parrotfeather infestation
Parrotfeather infestation, notice the dense mat of vegetation.

 Last updated October 01, 2008