Spotted knapweed is a biennial to short-lived perennial forb native to central Europe and Eastern Russia (Sheley et al. 1999). This species arrived in North America in the late 19th century as a contaminant in alfalfa seed and in soil used as ships' ballast.

The first record of spotted knapweed on the continent is from Victoria, British Columbia in 1883. Spotted knapweed may grow to more than one metre in height. It is less branched than diffuse knapweed and usually has darker, red-purple flowers.

Biennial to short-lived perennial

Spotted knapweed grows in a wide range of dry habitats from grasslands to forests although it prefers open sites with well-drained soils. Typically spotted knapweed occurs in areas that receive 30 to 50 cm of annual precipitation but does occur in drier areas. It is intolerant of complete shade. Usually invades disturbed sites but can then spread into adjacent undisturbed sites. Infestations can result in reduced yields of livestock forage and can displace native vegetation, particularly in areas of moderate grazing pressure.

Spotted knapweed reproduced exclusively by seed and each plant can produce up to 140,000 seeds. Seeds are dispersed primarily by wind, but most seeds land close to the parent plant. Seeds can also be dispersed in cut hay or bedding or on vehicle undercarriages. The seed banks of spotted knapweed can be extremely large and take years to manage using any control method available.

Widespread throughout the Cariboo Chilcotin Coast along transportation corridors and utility rights-of-way. The highest density of sites is along main highways, but it is also scattered elsewhere over most of the region. There are significant infestations in residential subdivisions throughout the region. The inventory for this species is well developed, although many secondary roads are known to contain unsurveyed spotted knapweed. There is a large infestation within the Thompson Nicola Regional District.