Diffuse Knapweed
Centaurea Diffusa


Provincial Noxious. Short-lived perennial or biennial.
Diffuse knapweed has hairy, greyish-green, split leaves on many branches growing from a single upright stem. The flowers are white or sometimes purple, with small, sharp, rigid spines on the bracts. Diffuse knapweed has a taproot and grows to 1 metre in height. It is found on grasslands, disturbed areas, and along roadsides in both rural and urban areas. It is one of 13 knapweed species in British Columbia.

Diffuse knapweed chokes out desirable forage for livestock and wildlife and increases soil erosion.

In British Columbia diffuse knapweed is found on grasslands, shrub lands, and dry open forests at low- to mid-elevations, but rarely on cultivated lands or irrigated pasture because it cannot tolerate cultivation or excessive moisture. It is found throughout southern British Columbia east of the Coast-Cascade Mountains and is considered a major concern in the Kootenay, Okanagan, Thompson, Cariboo, Omineca, and Peace River.

A single diffuse knapweed plant can produce up to 18,000 seeds which can remain dormant for years. Seeds are spread by wind, livestock, and humans, and are often dispersed over great distances when mature plants break at the stem and become tumbleweeds.

Weeds BC home Resources