Although usually called a biennial, teasel is better described as a monocarpic perennial. The period of time in the rosette stage apparently varies depending on the amount of time needed to acquire enough resources for flowering to occur. During the rosette stage leaves vary from somewhat ovoid in young plants to large and oblong leaves that are quite hairy in older rosettes. During the rosette stage teasel develops a large tap root. Cut-leaved teasel blooms from July through September, and common teasel blooms from June through October.
Stems also are prickly.
Teasel's unique inflorescence makes the plant readily identifiable when blooming. Flowers are small and packed into dense oval-shaped heads. Cut-leaved teasel usually has white flowers, while common teasel usually has purple flowers. Upper stem leaves of common teasel have smooth margins. Cut-leaved and common teasel should be accurately identified before attempting any control measures.