Luang Prabang prov., Ngoy distr., Don Khun village, near waterfall, around point 20°31'36.9''N 102°35'15.8''E. Remnants of primary evergreen forest on very steep rocky mountain slopes composed by solid marble like highly eroded limestone at elev. 450-550 m a.s.l. along mountain stream. Undershrub 1.5-2.5 m tall in open wet place. Flowers white with violet tint. Not rare.