Hook.f.
Description
Mussaenda roxburghii is a shrub of the eastern Himalayan and Indo-Burmese lowlands and foothills, ranging across India, Nepal, Bhutan, Bangladesh and Myanmar; GBIF logs some 145 occurrences including a few cultivated records farther afield. It grows in warm subtropical hill forest, along forest margins, stream banks, roadside thickets and clearings, generally from near sea level to about 1500 m. The photographed individual grows in Bhutan at Trithangebe beside a farmhouse at around 700 m in May, a typical habitat for this species, which thrives in the humid pre-monsoon warmth of the lower hills near villages.
The species is an erect to scrambling shrub with terete, finely pubescent young branches. The leaves are opposite, ovate to elliptic, acuminate, entire and softly hairy beneath, with interpetiolar stipules. The inflorescence is a terminal corymbose cyme of numerous small flowers; its most striking feature is the enlargement of a single calyx lobe of certain flowers into a large, white, leaf-like petaloid bract advertising the inflorescence. The fertile flowers have a narrowly tubular orange to yellow corolla with five spreading lobes and a hairy throat. The fruit is a small fleshy berry crowned by the persistent calyx and containing minute seeds.
Mussaenda roxburghii Hook.f. exemplifies the genus's showy semaphylls, the expanded white calyx lobes that aid pollinator attraction and recur across tropical Rubiaceae. Widespread and locally common through the Indo-Himalayan foothills, it is not regarded as threatened and persists in secondary vegetation. Related Himalayan congeners such as M. treutleri are sometimes confused with it, and the group remains a focus of regional taxonomic study.
Author: Hook.f. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of British India, taxonomic revisions of Mussaenda (Rubiaceae)