Dendrobium namdongense (D. sect. Dendrobium), a new miniature orchid from limestone mountains of northern Vietnam

Dendrobium namdongense is described here as a new species from limestone areas of the Nam Dong Conservation Area, Thanh Hoa Province, Quan Hoa District (northern Vietnam). This species inhabits primary evergreen broad-leaved and mixed forests on karstic limestone at elevations of 900–1100 m a.s.l. in a zone of humid, cool tropical climate. A detailed illustrated description and comparison of the discovered plant with the morphologically closest species, D. fuscifaucium and D. hekouense is provided, along with data on its distribution, ecology, and phenology. The new species has a potential in ornamental horticulture. According to the criteria of the IUCN Red List, the conservation status of the species is determined as Critically Endangered (CR).