Vietnam, Quang Binh Prov., Minh Hoa Distr., Dan Hoa municipality, Vietnam-Laotian border, around Cha Lo military station, point 17°42′50″N 105°45′54″E.
Broad-leaved primary forest on very steep slopes and along ridge of remnant mountain composed with highly eroded solid marble-like gray limestone at elevation 500-750 m a.s.l.
Tree to 8 m tall along ridge edge. Flowers light blue. Very common.
HAL 11772 20 April 2008 photo Coll.: L.Averyanov, P.K.Loc, N.T.Vinh, N.S.Khang