Spotted knapweed (Centaurea maculosa) is a non-native short-lived perennial forb that reproduces only by seed. A prolific seed producer, Spotted knapweed can produce up to 40,000 seeds per plant. The key to distinguishing spotted from other knapweeds is the black-tipped involucral bracts (phyllaries) at the base of the flower. Unlike diffuse knapweed, there is no long, distinct terminal spine at the tip of the bracts. Spotted knapweed can grow up to 4 feet tall on erect, ridged stems that are openly branched on the upper half of the plant. Urn-shaped flowers are solitary on the end of each branch tip. Flowers are pink to purple, and rarely white. Leaves are small, oblong in shape and pinnately divided. Multiple rosettes can form on a single spotted knapweed taproot crown. Flowers bloom June to October and seed set usually occurs by mid-August.
Spotted knapweed Fact Sheet