Provincial Noxious Biennial or short-lived perennial.
Spotted knapweed has hairy, deeply-cut leaves and purple (or occasionally
white) flowers on one or more upright stems. Flowerhead bracts
have a black-tipped fringe that gives a spotted appearance. Spotted
knapweed grows to a height of 1.5 metres and has a stout taproot.
Contact can cause skin irritation.
Spotted knapweed is a highly competitive weed that reduces or displaces
desirable forage in disturbed areas, and sometimes invades adjacent areas
that are relatively undisturbed. It forms near monocultures in some areas
of British Columbia.
This type of knapweed is widespread at low- to mid-elevation grasslands
and dry open forests. It has adapted to well-drained soils and can survive
in very dry climates such as those of Ashcroft and Osoyoos, but doesn't
like dense shade. Spotted knapweed occurs frequently in southern
British Columbia east of the Coast-Cascade Mountains and is present on
Vancouver Island and the mainland. It is a major concern in the Kootenay,
Okanagan, Thompson, Cariboo, Omineca, and Peace River regions.
This species is prolific, with individual plants producing up to 140,000
seeds per square metre. Although seeds are shed in the immediate area
around the parent plant, they are often spread much more widely in hay
and on vehicle undercarriages.