IDENTIFICATION
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.
DAMAGE
Diffuse knapweed chokes out desirable forage for livestock and
wildlife and increases soil erosion.
HABITAT
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.
SPREAD
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.
