Spotted knapweed

Genus: Centaurea

Species: maculosa

Description: A short-lived perennial, reproducing solely by seeds. Plant grows 2 - 4ft (.6-1.2m) tall and bear alternate, pale green leaves which are 1 to 3 inches long. Numerous flowers are produced from early July through August. Flowers are pink to light purple.

Where it grows: Seeds germinate in fall and early spring, highly adept at capturing available moisture and nutrients, and it quickly spreads, choking out other vegetation. Rapidly invades pasture, rangeland and fallow land and causes a serious decline in forage and crop production.

How it spreads: People are the major cause of spotted knapweed spread. The weed is spread readily in hay and on vehicle undercarriages.

What it threatens: Pasture and rangeland in Washington, Montana, Idaho, Oregon and California are infested with knapweed. In Oregon, it grows on 121,600 acres in 23 counties.

More information: DCNR website

Disclaimer - Clean Water Services does not endorse or recommend specific herbicides for use in controlling these species. To protect water quality, always follow herbicide label directions and obey application laws when using any herbicide.