Hook.f.
Description
Rhododendron aeruginosum is an evergreen shrub of the eastern Himalaya, native to Sikkim and the rest of India, Bhutan, Nepal and adjacent China. Its roughly 106 georeferenced records describe a narrowly distributed high-montane taxon. It grows in the upper subalpine to lower alpine belt, forming dense thickets on open slopes, ridges and rocky pasture above the treeline at roughly 3300-4400 m. The Sikkim collections noted above, from the Chopta valley at 3400-4100 m and Lada-La at 4000 m in June and August, are characteristic of its windswept, high-elevation habitat at and above the krummholz zone.
It is a compact shrub whose striking young leaves are covered with a thick, glaucous blue-green to verdigris waxy bloom, the epithet aeruginosum meaning "rust- or copper-coloured." The mature leaves are elliptic to oblong, leathery and coated beneath with a dense fawn to rufous indumentum. The flowers are borne in compact terminal trusses and are broadly campanulate, pale rose to white often flushed pink and spotted within, with ten stamens and a glabrous ovary. The fruit is a curved, woody, septicidal capsule releasing many small seeds.
Rhododendron aeruginosum is closely allied to R. campanulatum, under which name it has often been treated as a high-altitude variant or subspecies and to which the original web placement refers, the two distinguished chiefly by the glaucous juvenile foliage and dwarfer, more exposed habit of aeruginosum. It belongs to the large elepidote subgenus Hymenanthes and subsection Campanulata. Pollination is by bumblebees and other alpine insects. Its restricted high-altitude range makes it locally vulnerable to grazing, fire and the upslope compression of alpine shrubland under a warming climate.
Author: Hook.f. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, The Genus Rhododendron (Royal Botanic Garden Edinburgh) monograph