N.Vietnam, Thanh Hoa Prov., Quan Hoa Distr., Phu Le Municipality, Hang village, around point 20°31′48′'N, 105°04′40′'E. Dry secondary shrubs on clayey shale/sandstone/quartzite slope of river valley at foothills of rocky ridge composed with crystalline marble-like highly eroded limestone at elev. 100-200 m. Herb vine 6-8 m lg on open steep slope. Flowers blue. Very common.