Spotted knapweed has oval stalked cotyledons. The first true leaves are spoon shaped and have petioles, but later leaves become finely divided, are hairy, and form rosettes. The lower leaves tend to be deeply divided, whereas the upper leaves are less divided and more linear. Both upper and lower leaves are alternate. Mature plants are erect, branched and grow up to 1 meter tall.
Leaves are linear, alternately arranged, hairy and finely divided.
Flowers are pink to purple and sometimes white, and are surrounded by a bract with a dark black fringe. Spotted knapweed is a biennial or short lived perennial plant which reproduces by seed.