N.Vietnam, Cao Bang Prov., Trung Khanh Distr., Ngoc Khe Municipality, Pac Nga village, around point 22°54′59′'N, 106°31′44′'E, at elevation 750-850 m a.s.l.
Closed secondary and remnants of primary broad-leaved evergreen forest on very steep rocky slopes of rocky ridges and mesae composed with light gray solid marble-like highly eroded crystalline limestone.
Woody vine 20-25 m long. Flowers yellowish-white, later bright yellow. Rare.