N. Vietnam, Son La prov., Moc Chau distr., Long Luong municipality, near Sang Cai village (20°45′51′'N, 104°51′26′'E). Primary wet broad-leaved evergreen and semideciduous mossy forest along tops of remnant limestone highly eroded ridge at elev. 1500 m a.s.l. Herb vine 4-6 m lg. Flowers light yellowish-green. Not common.