FLORA OF VIETNAM
Orchidaceae
Dendrobium williamsonii Day & Rchb.f.

Ha Giang prov., Quan Ba distr., Bat Dai Son Nature Reserve, Bat Dai Son commune, Pai Chu Phin village, around point 23°07ʹ54.9ʺN 104°59ʹ24.1ʺE, 1000-1220 m a.s.l., karstic, highly eroded mountains composed of solid marble-like limestone, primary evergreen broad-leaved and coniferous (with Pseudotsuga sinensis) humid forest on steep rocky slopes near mountain tops. Clustering epiphyte on mossy tree near mountain top. Flowers white to light yellowish, lip with orange center. Not common. 16 April 2018, L. Averyanov, Nguyen Sinh Khang, Chuong Quang Ngan, T. Maisak, VR 326 (HN, LE01058169, LE01066707).