N. Vietnam, Tuyen Quang prov., Na Hang distr., Xuan Tam municipality, near Ban Cai village (22°29′18′'N, 105°19′47′'E). Primary broad-leaved evergreen forest on very steep slopes of highly eroded remnant limestone ridge at elev. 400-500 m a.s.l. Lithophytic herb up to 0.5 m hg on vertical cliffs. Common.