An annual plant, 15 – 40 cm tall, with an erect, downy stem, the flowers are arranged in dense, conical spikes of up to 30 flowers. The lower flowers are green, while the upper flowers are purple (or, rarely, white). The flat, opposing bracts are lanceolate. The plant flowers from June to August and is pollinated primarily by bumblebees. It grows on dry, sunny slopes, field borders, and waysides, preferring lime soil.