Alturas Field Office

Noxious Weeds


Spotted Knapweed   (Centaurea maculosa)
Sunflower Family   (Asteraceae)


Spotted Knapweed
Photo courtesy of the University of Idaho


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Description: Erect biennial or perennial with stout taproot. Stems 1 to 4 feet. Basal leaves up to 6 inches long, narrow, undivided to pinnately parted. Leaves of the mature plant finely divided. Flowers with pinkish-purple to cream ray flowers. Phyllaries stiff, tipped with a dark, comb-like fringe. Seeds about 1/8 inch long, tipped with tuft of persistent bristles.

Habitat: Native to Europe. Demonstrates aggressive growth in disturbed areas such as roadsides and waste areas, but also invades undisturbed areas in dry to moist rangelands. Spotted knapweed may release chemical substances which inhibit the growth of surrounding vegetation.

Distribution: Spotted Knapweed can be found in Susanville (Lassen County) and Big Bend (Shasta County) each having infestations of 10 acres or more. Scattered populations can be found along any of northeastern California's roadways, especially Highway 139 from Susanville to Klamath Falls, Oregon.

Flowering Period: June to October.