Northern Vietnam, Ha Tinh Prov., Huong Son Distr., Son Kim Municipality, in the vicinity of Rao An village, around point 18°22′00′'N, 105°13′13′'E. Primary evergreen lowland seasonal broad-leaved forest on granite rocky shady slopes of river valley at 260-360 m a.s.l. Herb 1-1.5 m hg among stream rocks in open place. Flowers dirty dull yellowish, calyx brown. Rare.