(Balf. f. & R.E. Cooper) Cullen
Description
Rhododendron dalhousieae var. rhabdotum is a striking epiphytic rhododendron of the eastern Himalaya. GBIF records this taxon from Bhutan, India and China, with only around 16 occurrences, reflecting its restricted range in the moist temperate forests of the eastern Himalaya. It grows chiefly as an epiphyte on mossy trunks, or on cliffs and steep banks, in humid broadleaved and conifer forest, generally between about 2000 and 3000 m. The plant illustrated was photographed at Tritangbi in Bhutan at 2250 m in May, flowering in late spring within the cloud-forest belt where high humidity and abundant moss support its epiphytic habit.
It is a straggling, sparsely branched shrub with large, leathery, oblong-elliptic leaves clustered toward the branch tips. The flowers are borne in a loose terminal truss of a few very large, fragrant, broadly funnel-form to campanulate blooms 8-10 cm long. The corolla is creamy white to pale yellow, and the diagnostic feature distinguishing var. rhabdotum from typical R. dalhousieae is the presence of bold longitudinal red stripes running down the outside of the corolla tube (the epithet rhabdotum, striped). The fruit is a dry septicidal capsule releasing numerous minute winged seeds suited to dispersal onto epiphytic perches.
The taxon belongs to Rhododendron section Maddenia, a group of large-flowered, often epiphytic and fragrant species centred on the eastern Himalaya. Cullen treated rhabdotum as a variety of R. dalhousieae, a placement some authorities raise to species rank as R. rhabdotum. Its large fragrant flowers are adapted to moth pollination. With a narrow range, specialised epiphytic ecology and dependence on intact humid forest, it is vulnerable to deforestation and is a prized but localised eastern Himalayan rhododendron.
Author: (Balf. f. & R.E. Cooper) Cullen · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, The Genus Rhododendron: its classification and synonymy (Cullen, RBGE)