Heracleum candidans var. obtusifolium

Description

Heracleum candidans var. obtusifolium (Wall. ex DC.) F.T.Pu & M.F.Watson is treated by GBIF as a synonym, with the accepted name being Heracleum candicans obtusifolium. It is a Himalayan umbellifer recorded from China and Nepal, GBIF documenting 44 occurrences, and is a plant of the upper subalpine and alpine zones. It occupies open slopes, meadow flushes, shrubberies and forest clearings, typically between about 3000 and 4200 m. The photographed plant at the Chele-La in western Bhutan, at roughly 3900 m in July, illustrates its association with the moist, high-elevation grasslands of the eastern Himalaya during the summer flowering season.

The plant is a robust, tomentose perennial with a stout rootstock and erect, ridged, hollow stems. The leaves are large and pinnately divided, with broad, lobed segments that are densely white-woolly beneath, the obtuse leaf segments giving the variety its epithet. The inflorescence is a large compound umbel with numerous rays subtended by deciduous bracts; the small flowers are white, with the marginal flowers often radiant and the outer petals enlarged and bilobed. The fruit is a dorsally compressed, broadly winged schizocarp bearing conspicuous oil ducts (vittae), the typical mericarp of the genus.

Heracleum is a taxonomically difficult genus in the Himalaya, with a continuum of closely allied entities; this taxon has been variously ranked as a species, subspecies or variety, and its placement under H. candicans reflects ongoing molecular and morphological reassessment of the group. As with other species of the genus, the foliage and sap contain furanocoumarins that may cause phototoxic dermatitis. The taxon is not regarded as threatened, though it occupies the narrow, climate-sensitive alpine belt of the central and eastern Himalaya.

Author: (Wall. ex DC.) F.T.Pu & M.F.Watson · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Flora of Nepal, Pimenov & Leonov genera of Umbelliferae