Wight
Description
Rhododendron griffithianum is an eastern Himalayan species centred on India (Sikkim, Arunachal), Bhutan, Nepal and adjacent China, with about 219 georeferenced records; further occurrences in Britain, the Netherlands, Canada, the United States and New Zealand reflect its long cultivation as a horticultural ornamental and parent of hybrids. It grows in cool, humid temperate forest, on shaded ridges and ravine sides, often as an understorey or forest-margin shrub between roughly 2500 and 3300 m. The photographed plants from Yatong-La at 3200 m and the East Nepal Milke Danda at 2800 m, flowering in May, typify this moist mid-montane belt.
It is a large evergreen shrub to small tree with smooth, peeling, reddish-brown bark. The leaves are elliptic-oblong, leathery, glabrous and somewhat glaucous beneath, with a rounded base and prominent midrib. The inflorescence is a lax truss of few large flowers; the corolla is broadly campanulate, white sometimes flushed pink, faintly fragrant, and among the largest of any Himalayan rhododendron, with a calyx that is unusually well developed and lobed. The fruit is an elongate, ribbed, dehiscent capsule releasing numerous minute winged seeds.
Classified in subgenus Hymenanthes, R. griffithianum has been horticulturally pivotal, contributing its size and corolla form to many hardy garden hybrids. In the wild it occupies a narrow, oceanic-monsoon climatic band, and its dependence on undisturbed humid forest renders it sensitive to logging, grazing and warming, of biogeographic interest as an indicator of the wet eastern Himalayan forest flora.
Author: Wight · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, The Genus Rhododendron (Royal Botanic Garden Edinburgh)