A perennial with branching, 4-angled stems and short, gray hair. Flowers in several terminal or near-terminal racemes, purplish blue. The arching upper lip is the “skullcap”; the lower lip is flat and 3-lobed. Blooms June-September. Leaves opposite, to 6 inches long, the largest toward center of stalk, ovate-lanceolate with a rounded base and coarse, blunt teeth, covered by fine hair. According to some, it is the seed-bearing structure that looks like a cap.