N. Vietnam, Son La prov., Moc Chau distr., Van Ho municipality, near Hua Tat village (20°46′35′'N, 104°46′31′'E). Primary broad-leaved evergreen closed forest on remnant limestone highly eroded ridge at elev. 1180-1250 m a.s.l. Lithophytic creeping herb among shady rocks. Abundant.