N. Vietnam, Hoa Binh prov., Da Bac distr., Cao Son municipality, Buoi Truong station near Ba Tri Mountain (20°52′31′'N, 105°11′48′'E). Secondary evergreen broad-leaved forest with bamboo on very steep shale slope with quartzite along river at 500-550 m a.s.l. Woody vine 10-12 m lg on open dry slope. Flowers white. Not common.