Hoa Binh Prov., Lac Son Distr., Tu Do Municipality, Mon village, around point 20°24′52”N 105°19′41”E. Secondary evergreen dry broad-leaved forest on steep rocky slopes of remnant mountain composed with highly eroded marble-like solid crystalline limestone at elevation about 300 m a.s.l. Very common. CPC 1386a 23 March 2011 Coll.: N.Q.Hieu, L.Averyanov, N.T.Hiep, P.K.Loc, P.V.The, N.T.Vinh, T.B.Ngan, N.Tap, D.D.Dao, V.T.Ha. Fl. in cultivation at 20 May 2016. Flowers purple.