Lindl.
Description
Dendrobium amplum (often treated under the segregate genus Epigeneium as E. amplum) is an epiphytic orchid distributed across the eastern Himalaya and adjacent Southeast Asia. GBIF documents 230 occurrences from China, India, Nepal, Bhutan, Myanmar, Bangladesh, Vietnam and Thailand, with herbarium and cultivated records also in Europe and North America. It inhabits mossy trunks and large branches in humid subtropical broadleaved forest, generally between roughly 1000 and 2000 m. The plant shown was recorded at Sandrup in Bhutan at 1400 m in October, a warm-temperate forest belt where seasonal monsoon moisture sustains a rich epiphytic flora.
The species has a creeping rhizome from which arise well-spaced, ovoid to fusiform pseudobulbs, each conspicuously four-angled and topped by two (rarely three) ovate-elliptic, coriaceous leaves. The inflorescence emerges from the apex of the pseudobulb and carries one to a few comparatively large, showy flowers. The spreading sepals and petals are pale green to yellowish, variously suffused or veined with brown and purple, while the three-lobed labellum bears a recurved, acute or apiculate midlobe and is marked with reddish-purple lines over a callused disc. The mentum is short and the column foot prominent.
Described by John Lindley, the species belongs to a group of broad-bulbed Dendrobium species frequently placed in Epigeneium, a genus whose limits remain debated; POWO accepts the Dendrobium placement. The autumn-flowering habit and large flowers make it attractive to collectors. While ranging widely and not formally listed as threatened, it depends on intact mature forest and is sensitive to habitat loss and over-collection.
Author: Lindl. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Orchids of Bhutan, Dendrobium and its Relatives (Lavarack et al.)