Houphan Prov., Hem Distr., Nacoc village, Puphadeng mountain, around point 20°09'52.6''N 103°10'19.4''E. Primary and secondary broad-leaved evergreen open dry forest on very steep rocky mountain slopes composed by solid marble like highly eroded limestone at elev. 1000-1200 m a.s.l. Shrub about 2 m tall on shady mountain slope. Flower buds pale yellowish. Common.