WSU Extension


Annual bluegrass 
Bentgrass, creeping 
Birdfoot Trefoil 
Bittercress (Shotweed, Hairy bittercress) 
Bittersweet nightshade (European bittersweet) 
Black medic 
Blackberry (Himalayan, Evergreen, Pacific) 
Blue mustard (Purple mustard, Tenella mustard) 
Brackenfern, western 
Bull thistle 
Buttercup, creeping 
Butterfly bush 
Canada thistle 
Catchweed bedstraw (Cleavers) 
Catsear, common (False dandelion) 
Chickweed, common and mouseear 
Creeping Jenny 
Dock (Curly, Broadleaf) 
Downy brome (Cheatgrass, Downy chess) 
Dwarf mistletoes 
English daisy (Lawn daisy) 
English ivy 
Field bindweed (Wild morningglory) 
Field pennycress (Fanweed) 
Foxtail (Green, Yellow, Bristly) 
Garden loosestrife 
Giant hogweed 
Ground ivy 
Groundsel, common 
Hedge bindweed 
Herb Robert (Robert geranium, stinky Bob) 
Horsetails (Scouringrush) 
Horseweed (Marestail) 
Knotweeds (Bohemian, Giant, Japanese, Himalayan) 
Lambsquarters, common 
Lesser celandine 
Mallow, common (Cheeseweed, Buttonweed) 
Oxalis (Creeping woodsorrel) 
Parrotfeather and Eurasian watermilfoil 
Plantain (Broadleaf, Buckhorn) 
Poison hemlock 
Poison ivy and Poison oak 
Prickly lettuce (China lettuce) 
Prostrate knotweed 
Puncturevine (Tackweed, Goathead) 
Purple deadnettle (Red deadnettle) 
Purple loosestrife (Purple lythrum) 
Purslane, common 
Red sorrel (Sheep sorrel) 
Redroot pigweed (Rough pigweed) 
Redstem filaree (Stork's bill, Crane's bill) 
Reed canarygrass 
Russian thistle (Tumbleweed) 
Ryegrass, annual (Italian ryegrass) 
Salsify (Goatsbeard) 
Scotch broom 
Sowthistle, annual and perennial 
Spurges (Prostrate spurges) 
St. Johnswort, common (Goatweed, Klamathweed) 
Stinging nettle 
Tansy ragwort 
Tumblemustard (Jim Hill mustard) 
Velvetgrass (Common velvetgrass) 
Water primrose 
Waterhemlock, western 
Wild carrot (Queen Anne's lace) 
Yellow nutsedge 

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Caption: Partotfeather fronds
Photo by: T.W. Miller
Weeds : Parrotfeather and Eurasian watermilfoil : Myriophyllum spp.
(revision date: 4/5/2016)

Family: Haloragaceae
Cycle: Perennial
Plant Type: Broadleaf aquatic

Use Integrated Pest Management (IPM) for successful weed management.

These rhizomatous perennials exhibit an annual pattern of growth. In the spring, shoots begin to grow rapidly from overwintering rhizomes as water temperatures increase. Rhizomes function as a support structure for adventitious roots and provide buoyancy for emergent growth during the summer. Emergent stems and leaves extend from a few inches to over one foot above the water's surface. Underwater leaves tend to die back and drop off as the season advances. Bright green emergent leaves are 1/2 inch to 1 inch long and have six to 18 divisions per leaf. Plants usually flower in the spring but some plants may also flower in the fall. The inconspicuous flowers form where the emergent leaves attach to the stem. Parrotfeather typically dies back to the rhizomes in autumn. Unlike Eurasian watermilfoil, parrotfeather does not form autofragments. However, fragments can be formed mechanically and will readily root. A related species, variable-leaf milfoil (M. heterophyllum), is sometimes used as an aquarium plant. All three species may be spread by moving plant fragments on boats, trailers, or water equipment. SPECIAL INFORMATION: Parrotfeather and Eurasian watermilfoil adversely impact aquatic ecosystems by forming dense canopies that shade out native vegetation. Monospecific stands of either species provide poor habitat for waterfowl, fish, and other wildlife. In WASHINGTON and OREGON, parrotfeather and Eurasian watermilfoil are designated as Class 'B' noxious weeds. Management of these species may be required by law in your county. In addition, both species are on the Washington and Oregon noxious weed quarantine lists, which prohibit sale, purchase, and transport of plants, seeds, and plant parts. Variable-leaf milfoil is a Class 'A' noxious weed in WASHINGTON; control is REQUIRED by law. Consult your county Noxious Weed Control Board for more information.
Parrotfeather (Myriophyllum aquaticum) and Eurasian watermilfoil (M. spicatum) are found throughout southwestern Washington in freshwater lakes, ponds, streams, and canals. They appear to be adapted to high nutrient environments, and tend to colonize slowly-moving or still water rather than areas with higher flow rates. While they grow best when rooted in shallow water, they have been known to occur as floating plants in the deep water of nutrient-enriched lakes. The emergent stems can survive on wet banks of rivers and lake shores, so they are well adapted to moderate water level fluctuations. With tough rhizomes, parrotfeather and watermilfoil can be transported long distances on boat trailers.

Management Options

Non-Chemical Management
  • Reduce weed infestation by handpulling weeds.
  • Digging and carefully removing all rhizomes will effectively eliminate single plants and small infestations.
Select non-chemical management options as your first choice!

Chemical Management

Handpulling and digging is only effective on small infestations. Do not use mechanical control methods as they will increase the rate of spread! Applications should be made by those holding a current aquatic pest control license. In Washington, a special permit is required for use of herbicides in aquatic sites. Contact the Washington Department of Ecology or the Washington State Noxious Weed Control Board for more information.


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Caption: Partotfeather fronds
Photo by: T.W. Miller
Caption: Eurasian watermilfoil
Photo by: Washington Noxious Weed Board slide collection