The stems may reach 2 to 3 feet high and are usually purple-spotted.
Leaves are alternate, simple, and toothed.
Inconspicuous male flowers are grouped in round clusters at the top, the conspicuous female flowers are at the base. Involucral bracts of the female flower ultimately form an ellipsoid, hardened prickly bur. The prickles art hooked at the tip. The male flowers drop off quickly, but the burs remain, protecting the two blackish achenes. The burs are spread to other areas by sticking to animals and clothing.