N. Vietnam, Thanh Hoa prov., Ba Thuoc distr., Co Lung municipality, territory of Pu Luong protected area, near Co Lung village (20°27′28′'N, 105°12′18′'E). Primary broad-leaved evergreen very wet forest in valley between remnant highly eroded karst limestone ridge at elev. 400 m a.s.l. Woody vine 4-6 m lg on open rocky place. Flowers light green. Not rare.