Son La Prov., Moc Chau Distr., Chieng Son comm., about 1 km to NE from Chieng Son village, around point 20°46′02.0N 104°37′03.1E.
Remnants of primary broad-leaved evergreen forest on tops of hills composed with karstic highly eroded yellow-white limestone at elevation 1100-1050 m a.s.l.
Semi-woody vine 3-5 m long in open place. Flowers greenish. Not rare.