D.G. Long.
Description
Corydalis calliantha is a high-alpine herb of the Eastern Himalaya, narrowly endemic to Bhutan, where it is the only territory from which it is documented (GBIF records derive exclusively from BT, with very few verified occurrences). It occupies the upper alpine and subnival belt, growing among moist screes, moraine debris and damp turf at the margins of glacial tarns. The collection illustrated here, gathered along the Ludlow-Sherriff Trail near Dem-Tso at about 4600 m in July, typifies its preference for cool, well-drained but seasonally irrigated substrates exposed only briefly during the short alpine summer.
It is a low, tufted, glabrous and somewhat glaucous perennial arising from a slender fleshy rootstock. The leaves are mostly basal, petiolate and several times finely divided into small obovate to oblong segments, giving a delicate, almost ferny appearance. Flowers are borne in short, few-flowered racemes; each zygomorphic flower has four petals, the outer upper petal produced backward into a slender, gently curved nectar spur, and is typically clear sky-blue to violet-blue, the colour to which the epithet calliantha ("beautiful-flowered") alludes. The fruit is a slender dehiscent capsule containing several small, shining black seeds, each often bearing a small elaiosome.
Within the large and taxonomically intricate genus Corydalis, this species belongs to the blue-flowered alpine assemblage centred on the Sino-Himalayan region, a group much studied by D.G. Long and collaborators in the Flora of Bhutan. Its restricted range and specialised subnival habitat make it of biogeographic interest and potentially vulnerable to climatic shifts affecting high-altitude snowmelt, although its remote terrain affords protection from direct disturbance.
Author: D.G. Long. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, Liden & Zetterlund monograph of Corydalis