N. Vietnam, Thanh Hoa prov., Ba Thuoc distr., Co Lung municipality, territory of Pu Luong protected area, near Co Lung village, Nui Doan (Pha Doan) mountain system (20°26′30′'N, 105°11′32′'E). Primary evergreen broad-leaved dry forest on steep slopes of remnant highly eroded karst limestone ridge at elev. 350-450 m a.s.l. Woody vine up to 5 m hg. Flowers light-yellowish. Not common.