Grewia souladethiana, a new species of Malvaceae from Laos

Grewia souladethiana (Malvaceae-Grewioideae) is described and illustrated from Phou Hin Poun National Park, Khammouane Province, in central Laos. The new species grows at the edge of evergreen broad-leaved forest and in open grassland on the foot of limestone hills. To confirm the validity of the new species, diagnostic morphological characters were compared based on literature and herbarium materials at BKF, FOF, KAG an VNM as well as online digitized images.

Morphologically it is similar to G. thailandica in having acuminate leaf apex, serrate leaf margin, and axillary inflorescences which are 2‒3-flowered and with erect peduncle, but distinguished by its tree habit, shorter petioles, smaller sepals and petals, and solitary or 2-lobed fruits. A description, photographs, line drawings, vernacular name and preliminary conservation status are provided for it, as well as a key to species of Grewia in Laos is provided.