N.Vietnam, Bac Kan Prov., Cho Don Distr., Ban Thi Municipality, village Phia Khao, around point 22°17′31′'N, 105°31′51′'E, Cau Muc mountain at elevation 800-900 m a.s.l.
Primary broad-leaved evergreen closed forest on very steep slopes and cliffs near tops of rocky ridge composed with solid marble-like stratified limestone.
Terrestrial and lithophytic herb on shelves of vertical cliff. Flowers blue. Common on tops of ridge.