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 along tops of remnant highly eroded
karst limestone ridge at elev. 500-550 m a.s.l. Woody vine 2-3 m hg on steep rocky slope. Flowers dull yellow. Rare.