N. Vietnam, Hoa Binh prov., Mai Chau distr., Hang Kia municipality, near Hang Kia villages (20°43′39′'N, 104°53′43′'E). Secondary broad-leaved evergreen wet forest on very steep slopes of remnant limestone highly eroded ridge at elev. 900 m a.s.l. Herb vine 3-4 m hg in open wet place. Flowers white, center dirty blue. Common.