Phyllostegia floribunda, a member of the Lamiaceae (mint) family, is a small shrub or subshrub with hairy stems. Leaves are opposite and ovate, lanceolate, or elliptic, 12 to 24 cm (4.7 to 9.4 in) long and 4.5 to 8.5 cm (1.8 to 3.3 in) wide, variably hairy (ranges from almost hairless to densely covered with soft hairs), with a pale lower surface; margins toothed; petioles 2.5 to 6.5 cm (1 to 2.6 in) long and hairy. Flowers are borne in axillary (where the leaf petiole meets the stem) inflorescences; flowers are two per whorl, pedicels (flower stems) are 8 to 10 mm (0.3 to 0.4 in) long; calyx is obconical (the point of attachment at the small end), 2 to 5 mm (0.07 to 0.2 in) long, hairy, with 10 veins, teeth linear-lanceolate and 1.2 to 2.4 mm (0.05 to 0.1 in) long. Flowers are maroon to red and covered with long soft hairs, floral tube 8 to 10 mm (0.3 to 0.4 in) long with two unequal lips 2.5 and 5 mm (0.1 and 0.2 in) long; four short-styled stamens. Fruits are composed of four fleshy nutlets, 3 to 3.5 mm (0.1 to 0.13 in) long and shiny black when mature.