Son La Prov., Yen Chau Distr., Muong Lum Municipality, Xao village, around point 20°59′54″N 104°38′47″E.
Broad-leaved and coniferous (with Pinus kwangtungensis and Calocedrus rupestris) evergreen forest on steep slopes and on tops of ridge composed with rocky crystalline solid marble-like highly eroded limestone at elev. 1100-1300 m a.s.l.
Herbaceous vine 1-2 m long on open mossy rocky slope. Flowers white. Rare.
HAL 9495 04 Nov. 2006 Photo. Coll.: Nguyen Tien Hiep, L.Averyanov, Pham Van The.