(Hook.) Sweet
Description
Piptanthus nepalensis is a Sino-Himalayan shrub distributed along the southern flank of the great ranges from Nepal and northern India eastward through Bhutan into south-western China (Yunnan, Sichuan, Xizang), with outlying records in Myanmar; the species is widely cultivated and naturalised in temperate gardens, accounting for the European, North American and Antipodean records (GB, DE, BE, NL, US, CA, NZ) among its more than 1600 georeferenced occurrences. It favours open scrub, forest margins, rocky slopes and stream banks in the upper montane and subalpine belts, typically between about 2500 and 4000 m. The populations on the Bhutanese passes of Tumching-La (3000 m) and Chele-La (3300 m), flowering with the spring thaw in May, are characteristic of its habitat among Rhododendron and conifer scrub.
It is a deciduous to semi-evergreen shrub reaching 1-4 m, with stout greenish branchlets bearing silky-pubescent young growth. The leaves are trifoliolate, long-petiolate and stipulate, the leaflets elliptic to lanceolate, dark green and glabrescent above, glaucous and appressed-silky beneath. The showy golden-yellow papilionaceous flowers, 2.5-3 cm long, are borne in terminal erect racemes; the calyx is bilabiate and silky, and the standard, wings and keel are typical of the tribe Thermopsideae. The fruit is a flattened, elongate, dehiscent legume to 12 cm, glaucous-pubescent and containing several dark reniform seeds.
Piptanthus is a small genus of the broadly defined Thermopsideae allied to Thermopsis and Anagyris, distinguished by its woody habit and trifoliolate leaves. Long-cultivated for its early bloom, P. nepalensis hosts nitrogen-fixing rhizobia that aid colonisation of skeletal soils. It is not considered threatened, being abundant across a broad range, though its toxic quinolizidine alkaloids deter browsing.
Author: (Hook.) Sweet · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Flora of Nepal, Turner's revision of Piptanthus (Thermopsideae)