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Spotted Knapweed

Centaurea biebersteinii

Identifying Characteristics

  • 20-120 cm tall
  • pink, white or purple flowers bloom from July to October
  • flowers resemble small thistles growing at the end of clustered branches
  • identified by small black fringe on the flower head
  • multi-divided stem leaves decrease in size closer to the shoot
This is a photograph of Knapweed. 5 images
This is a map of British Columbia showing the spread of invasive species.
Report a Sighting

The super villain of weeds.

Spotted Knapweed is just one of many species of invasive knapweed in the province. It is found in grasslands, pastures and shrub lands, including the south Okanagan Valley's antelope-brush grasslands - an endangered ecosystem.

Impact on Communities and Native Species

Knapweed is a highly competitive plant that quickly and easily crowds out native grass and plant species. More than 40,000 hectares of land in the province are infested with knapweed and this could easily spread to over a million hectares. Agriculture is British Columbia's third largest industry, and alien species such as Knapweed put farming at risk by invading grazing areas. Knapweed forms dense infestations and its deep taproots drill into the ground, impacting soil stability and capturing water before native species are able to. These roots also produce chemicals that prevent seeds of other plants from growing. Knapweed has bitter leaves that keep domestic and wild animals from grazing on it. Not only does knapweed impact native plant species, it also threatens wildlife such as elk and deer. These animals rely on range grasses for up to 80 per cent of their diet, and knapweed infestations can push out this important food source.

Invasion History

Spotted Knapweed is native to Europe and likely arrived in British Columbia accidentally, perhaps mixed with the seeds of agricultural crops or in contaminated hay. It has been reported in North America since the early 1900s. Knapweed has been spread primarily by humans. It gets caught and transported on cars, trains, aircraft and logging trucks. Florists use it in arrangements, and it hides in hay and with other seeds.