N. Vietnam, Prov. Cao Bang, distr. Tra Linh, municipalite Quoc Toan, vicinity of Thang Heng and Lung Tao villages near Thang Heng lake at 500 m alt. Open clayey alluvial banks of karst lake periodically flooded with water. Shrub up to 2 m hg, forming very dense monodominante tuft-shrub thickets near highest water-line of the lake. Flowers pink. VH 4862 25-27.05.1997 International Botanical Expedition of the U.S.A. National Geographic Society (grant No 5803-96)