(Raym.-Hamet) H. Ohba
Description
Rhodiola prainii is a high-alpine succulent of the Himalaya and Tibetan borderlands, recorded by GBIF (98 occurrences) from Nepal, China, India and Bhutan (NP, CN, IN, BT). It grows on open, well-drained alpine substrates — rocky slopes, screes, cliff ledges, moraine and turf — in the upper subalpine to alpine zone, typically between about 3800 and 4800 m. The collection illustrated from Baga-La-Phedi in West Nepal at around 4200 m in July, the peak of the short monsoon-summer growing season, is representative of its habitat: cold, intensely insolated, seasonally moist ground above the treeline.
Like other members of the genus it is a perennial herb with a stout, fleshy, branched caudex or rhizome crowned by persistent old leaf-bases and giving rise to several short, erect, glabrous flowering stems. The leaves are alternate, sessile, succulent, oblong to obovate or spathulate, entire or sparsely toothed toward the apex, and rather crowded. The inflorescence is a dense terminal corymb or cyme; the flowers are small, usually 4-5-merous and functionally unisexual (the species dioecious), with narrow petals in shades of greenish-yellow to reddish. The fruit is a cluster of erect, beaked follicles releasing minute seeds.
Rhodiola prainii sits within the predominantly Sino-Himalayan genus Rhodiola (Crassulaceae, subfamily Sempervivoideae), segregated from Sedum on its thick perennating rootstock, scale-leaved lower stem and frequently dioecious flowers. The genus is renowned for tissues rich in salidroside and rosavin, and several species are harvested as adaptogenic 'golden root'. Such collection pressure, combined with the slow growth and narrow alpine niche characteristic of the group, makes high-elevation Rhodiola populations vulnerable to over-exploitation and climate-driven habitat contraction.
Author: (Raym.-Hamet) H. Ohba · Sources: POWO (Kew), GBIF, Flora of China, Annotated Checklist of the Flowering Plants of Nepal, Ohba Monograph of the Genus Rhodiola, Crassulaceae of the Himalaya