Cao Bang Prov., Nguyen Binh Distr., Ca Thanh Municipality, Cao Lu village, around point 22°42'47.7"N, 105°51'50.8"E. Primary coniferous forest with Pseudotsuga sinensis along highly eroded rocky limestone ridge at elevation about 1300 m a.s.l. Herbaceous vine to 4 m long among open mossy rocks. Flowers yellow. Common.