Tall, thistlelike biennials with stout, straight, ridged, prickly, branching stems. Grows from a basal rosette whose leaves can vary from egg-shaped to large and oblong and can be quite hairy or prickly with age. The taproot may be more than 2 feet long and 1 inch in diameter at the crown. Blooms June–October. Flowers are tiny, massed on a cylindrical head, each with a tubular corolla, with stiff, narrow, pointed bracts longer than the flowers. The flowerheads form at the tops of the stems. Leaves on flowering plants are large, opposite, stemless, and prickly, especially on the lower midrib.
Two species in Missouri: Common teasel (Dipsacus fullonum) has lilac to lavender flowers; the stem leaves are oblong, lanceolate, scalloped or bluntly toothed, opposite, and sometimes slightly fused at the bases. Cut-leaved teasel (D. laciniatus) has white flowers; the stem leaves are irregularly pinnately lobed and prominently fused toward the bases, forming cups that may hold water.