N. Vietnam, Hoa Binh prov., Da Bac distr., to the SW of Doan Ket village (20°54′01′'N, 105°04′19′'E). Primary broad-leaved evergreen forest on very steep slopes of remnant highly eroded limestone ridge at elev. 700-750 m a.s.l. Lithophyte and terrestrial herb on open wet rocky slope. Flowers white, anthers yellow. Not common.