Northern Vietnam, Ha Tinh Prov., Huong Son Distr., Son Kim Municipality, Rao An village, around point 18°25′37′'N, 105°13′14′'E. Secondary open evergreen lowland seasonal broad-leaved forest on steep granite slopes along rocky river at 140-200 m a.s.l. Woody vine about 10 m lg. Flowers: tepals gray, stamens brown. Not common.