From 1-3 ft in height. Stiffly branching with branches more or less erect and roughly ridged. Leaves of the basal rosette are 6 inches long. Flowering period is from June to September. Flower head bracts have dark fringe at top resembling a spot.
Spotted knapweed is a biennial or short-lived perennial that is generally somewhat woolly.
All knapweeds may contain a cancer causing agent. Integrated management is necessary to control this weed. Herbicide application can work. Consult you local weed control office for more information. 12 insect species are cleared for use by the USDA to control spotted knapweed.