N. Vietnam, Thanh Hoa prov., Ba Thuoc distr., Co Lung municipality, territory of Pu Luong protected area, near Pu Luong village (20°27′01′'N, 105°11′03′'E). Primary very dry evergreen broad-leaved forest with Burrettiodendron hsienmu along tops of remnant karst limestone ridge at elev. 500-550 m a.s.l.. Terrestrial and lithophyte herb on very steep slope and vertical cliffs. Flowers white. Very common.