N. Vietnam, Thai Nguyen prov., Dong Hy distr., Tan Long municipality, vicinities of Mo Ba village (21°46′21′'N, 105°52′07′'E). Primary wet broad-leaved evergreen closed forest (with Burettiodendron hsienmu as a main dominant) on remnant highly eroded limestone ridge at elev. 400-450 m a.s.l. Terrestrial and lithophyte herb 1-1.5 m hg in shady wet places. Leaves below deep violet. Common.