Vervain is a perennial erect herb plant, reaching up to 120 cm in height. The base becomes woody. The leaves are opposite, ovate to lanceolate, covered with hard hairs on both sides, with the hairs denser on the veins below. The flowering spikes are terminal or axillary, bearing blue-purple flowers, sessile, with a membranous calyx, tubular, a corolla slightly bilabiate, and short filaments. The ovary is hairless, and the fruit is enclosed within the calyx, forming small nuts. Flowering and fruiting period is from June to October.