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.