Tualatin Riverkeepers are needed to help control noxious weeds in the Tualatin River watershed by reporting weed sightings to Tualatin Riverkeepers Watershed Watch Hotline. These species are displacing native plants, causing extreme erosion, and diminishing water quality. Noxious weeds are spreading rapidly through the riparian corridor of the Tualatin River and its tributaries.
Tualatin Riverkeepers, in partnership with Clean Water Services and the Tualatin Hills Parks and Recreation District have formed the Tualatin Basin Invasive Species Working Group (TBISWG). TBISWG is conducting a basin wide effort to eradicate invasive plant species that threaten to damage our community’s natural resources.
TBISWG is conducting outreach to municipalities within the Tualatin basin to coordinate a treatment action plan. The members are offering to coordinate this effort and provide support to municipalities by supplying information on species identification and treatment methods.
Tualatin Riverkeepers received a small grant from Metro Parks and Greenspaces to coordinate weed control efforts in the watershed.
TOP FIVE WEEDS TO WATCH
We have cooperatively identified the most threatening invasive plant species in our watershed. They are Japanese Knotweed, Meadow Knapweed, Giant Hogweed, Garlic Mustard and Purple Loosestrife. Identification and reporting on invasive species is the first step towards eradicating noxious weeds! Thanks for your help.
Learn to identify 16 weeds to report as well as other troublesome invasive plants at Clean Water Services' Non-Native Invaders Web Page.
If you spot a potential invasive species in Oregon, use use the Oregon Invasive Species Hotline online form to report it or call the toll-free number 1-866-INVADER.
Invasive speciesinfo from Clean Water Services.
Japanese Knotweed and Giant Knotweed are herbaceous perennials. They grow to over 10 feet when mature. The size of leaves may vary, normally about 6 inches long x 3 - 4 inches wide, oval to somewhat triangular and pointed at the tip. Flowers appear in sprays in summer and are greenish white in color. Knotweed spreads primarily in along streams and riverbanks and grows in wetlands.
A member of the carrot or parsley family, Giant Hogweed grows 10-15 ft tall. The white flowers are on a large umbrella-shaped head that can be nearly 3 feet in diameter. Hogweed blooms mid-May to July. The plant also has a stout dark reddish-purple stem and spotted leaf stalks.
Caution: Sap from the Giant Hogweed may cause serious burns to skin when exposed to sunlight. Oregon Department of Agriculture and the City of Tigard are working to eradicate Giant Hogweed from lower Fanno Creek.
Photo: The Nature Conservancy
Purple loosetrife is a perennial that blooms midsummer. It grows up to 7 ft tall and is an upright bushy plant. Flowers are pink to purple, possessing 5-6 petals and numerous on a long spike. Spreads by seed and spreading rhizomes that form dense, woody mats.
Its showy purple flowers crown a vigorous plant that crowds out marsh vegetation required by wildlife for food and shelter. Decreased waterfowl and songbird production has been well documented in heavily infested marshes. This former ornamental species can be found along wetlands, stream banks, and shorelines of shallow ponds.
Garlic mustard monopolizes light, moisture, nutrients, soil and space to quickly establish a monoculture groundcover, excluding native plants and depriving wildlife of essential food and shelter.
Garlic Mustard produces toxins in the soil that prevents other plants from becoming established. It grows 12-48 inches and has small white flowers in April/May. Garlic Mustard has a two-year life cycle: Year one leaves are kidney shaped, 2nd year leaves are sharply toothed and triangular. It gives off a garlic odor when crushed.
Photo: Oregon Dept of Agriculture
Meadow Knapweed and Spotted Knapweed bloom in midsummer to fall. They grow from woody root crown and up to 3 1/2 feet tall. The lower leaves are long-stalked, upper leaves have no stalk. Stems are many-branched and tipped by a solitary flower head up to one inch wide. Flower heads are pink to reddish purple, oval or almost globe-shaped. A key identifying feature is the fringed bracts on the flower head. A hybrid of black and brown knapweeds. Its foliage is coarse and tough. However, because meadow knapweed is a hybrid, it traits can vary.