Perennial aromatic herb.  Stems erect or ascending, 30-90 cm long, branched, glabrous; leaves lanceolate, acute, blade punctate; flowers in large terminal spikes, 2.5-7.5 cm long, the ones at the sides being longer than the one in the middle, calyx glabrous, with acute teeth, usually ciliate; corolla purple, rarely white, glabrous.

The typical botanical description may vary due to the existence of varieties within the species.