Ha Giang prov., Quan Ba distr., Tung Vai commune, Thang village, around point 23°03ʹ00.4ʺN 104°52ʹ02.2ʺE, steep rocky slopes of river valley composed with eroded limestone at elevation 1000–1060 m a.s.l. Remnants of primary evergreen broad-leaved very humid forest. Lithophytic sedge on open wet mossy river rocks. Very common. 19 October 2018, L. Averyanov, Nguyen Sinh Khang, T. Maisak, Truong Quang Ngan, VR 1035 (HN, LE01049106, LE01049119).