N. Vietnam, Tuyen Quang prov., Na Hang distr., Thanh Tuong municipality, near Ban Bung village (22°16′26′'N, 105°25′58′'E). Primary broad-leaved evergreen wet forest on very steep limestone slopes of highly eroded remnant limestone ridge at elev. 350 m a.s.l. Terrestrial herb up to 2 m hg along rocky wet stream slope. Flowers yellow, keels brown. Locally common.