Phyllostegia mannii, a nonaromatic member of the Lamiaceae (mint) family, is a climbing vine with many-branched, four-sided, hairy stems. The opposite, hairy leaves are shaped like narrow triangles or narrow triangular ovals and are 2 to 5.5 cm (0.8 to 2.2 in) long and 0.7 to 2.3 cm (0.3 to 0.9 in) wide with coarsely toothed margins. Clusters of four to six flowers are arranged in each of several false whorls along an unbranched flowering stem 4 to 15 cm (1.6 to 6 in) long. The calyx is a bell-shaped, lobed structure. The slightly curved, two-lipped white corolla tube is about 7 to 8 mm (0.3 in) long. The fleshy, dark green to black nutlets 2 to 2.5 mm (0.08 to 0.1 in) long.