Between 1980 and the present, the range of spotted knapweed rapidly increased to include 326 counties in the western United States, including every county in Washington, Idaho, Montana, and Wyoming. Spotted knapweed invasion is associated with reductions in biodiversity, wildlife and livestock forage, and increased soil erosion. Basal rosette leaves are borne on short stalks and grow up t 8 inches long and 2 inches wide. Rosette leaves are deeply divided into lobes on both sides of the center vein. Flowering stems stand 8 inches to 4 feet tall.
Spotted knapweed stems branch on their upper half.
Spotted knapweed also has a black margin at the bract tips, and obvious dark longitudinal veins. Spotted knapweed flowers are purple to pink, rarely white, with 25 to 35 flowers per head. Spotted knapweed flowers bloom from June to October. The flowerheads usually remain on the plant. The native range of spotted knapweed is central Europe and east to central Russia, Caucasia, and western Siberia.