(Centaurea maculosa Lam.)
Sunflower family - Asteraceae
Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.
Growth Habit: Biennial or short lived perennial, up to 3 ft. tall. Rosette formed first year, flowering stalk elongates second year.
Leaves: Long and divided below, short and narrow above. Covered with fine hair.
Stem: Erect with slender wiry branches. Covered with fine hair.
Flower: Seed heads mostly on branch tips, solitary to 1" diameter. Pink to purple, rarely white. Seed head bracts are black tipped, with 5 to 7 pairs of short feathery appendages.
Roots: Taproot not well developed.
Seeds: Brownish, 1.8" long, notched on one side of base, short tuft of bristles at tip end.
Habitat: Well-drained, light soils receiving summer rainfall. Rangelands.
Biological Controls: Sulphur knapweed moth (Agapeta zoegana), Knapweed root weevil (Cyphocleonus achates), Lesser knapweed flower weevil (Larinus minutus), Broad-nosed seed head weevil (Bangasternus fausti).
Herbicides: 2,4-D, 2,4-D & Tordon, Curtail, Milestone.