N. Vietnam, Hoa Binh prov., Mai Chau distr., Hang Kia municipality, near Hang Kia village (20°43′39′'N, 104°53′43′'E). Primary broad-leaved evergreen wet forest on remnant limestone highly eroded ridge at elev. 1100-1300 m a.s.l. Shrub 1-1.5 m on open mossy rocks on tops of ridge. Flowers white, anthers yellow. Locally very common.