Lindl.
Description
Dendrobium longicornu is an epiphytic orchid widespread across the eastern Himalaya and Indo-Burmese region, with GBIF recording over 300 occurrences and native range spanning India, China, Nepal, Bhutan, Vietnam, Myanmar, Bangladesh and Thailand, besides cultivated records in Europe. It grows as an epiphyte on mossy trunks and branches in humid, temperate to subtropical broad-leaved forest, typically between about 1500 and 2700 m. Bhutanese material was photographed at Trontsa (2300 m), Wangdi and Pemagatse (both 2600 m) in September and October, flowering on shaded, moss-laden trees in cool montane woodland.
The plant forms tufted, slender, erect to pendulous stems clothed in black-hairy leaf sheaths, bearing thin, lanceolate leaves toward the apex. The flowers, borne singly or few together near the stem tips, are showy and predominantly white with a fringed labellum marked by orange to greenish veining in the throat. The narrow tepals are spreading; the diagnostic feature is the long, slender, horn-like spur (mentum) formed by the lateral sepals and column foot, from which the epithet "longicornu" derives. The column is short, the anther cap bearing waxy pollinia, and the fruit a ribbed capsule.
Within the large genus Dendrobium, this species belongs to the white-flowered Formosae (nigrohirsute) section, distinguished by the dark hairs on stems and sheaths. Although widespread, it is sought by orchid collectors and is affected by habitat loss and overharvesting; like all Dendrobium it is listed on CITES Appendix II, regulating international trade.
Author: Lindl. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Orchids of Bhutan (Pearce & Cribb), CITES Appendix II listing