Phyllostegia glabra var. lanaiensis is a robust, erect to decumbent, glabrous, perennial herb in the Lamiaceae (mint) family. Its leaves are thin, narrow, lance-shaped, 8 to 24 cm (3 to 9.5 in) long and 1.6 to 2.5 cm (0.6 to 1 in) wide, often red-tinged or with red veins, and toothed at their edges. The flowers are in clusters of 6 to 10 per leaf axil, mostly only at the ends of branches. The flowers are white, occasionally tinged with purple, and are variable in size, about 1 to 2.5 cm (0.4 to 1 in) long. The fruit consists of four small, fleshy nutlets.