Vientiane prov., Kasi distr., between San and Tham Tai villages, around point 19°17'47.9''N 102°08'58.9''E. Secondary broad-leaved evergreen dry forest on very steep rocky mountain slopes composed by solid marble like highly eroded limestone at elev. 900-1000 m a.s.l. Undershrub or small shrub 2-2.5 m tall in shady rocky place. Flowers light purple-violet. Common.