Northern Vietnam, Ha Tinh Prov., Huong Son Distr., Son Kim Municipality, in the vicinity of Rao An village, around point 18°24′30′'N, 105°13′13′'E. Remnants of primary evergreen lowland seasonal broad-leaved forest on very steep granite/shale slopes of rocky river canyon at 180-200 m a.s.l. Woody vine 15-20 m lg in open place. Flowers light yellowish-green with dirty purple-brown center. Not common.