Kitam.
Description
Aster nakaoi is a high-montane perennial of the Eastern Himalaya, presently documented chiefly from Bhutan and adjacent Sikkim and southern Tibet, where it occupies the upper temperate to subalpine belt. The species is poorly represented in aggregated occurrence databases, reflecting its restricted range and infrequent collection rather than true rarity. It favours open grassy slopes, the margins of Rhododendron and Abies forest, rocky banks and the verges of alpine meadows, typically between about 3000 and 4000 m. The plant illustrated here was photographed near Paro in western Bhutan at roughly 3300 m in May, when the earliest flowering heads appear among emerging summer herbage.
The plant forms low tufts arising from a short, somewhat woody rhizome bearing fibrous roots. Stems are erect to ascending, simple or sparingly branched above and often shortly pubescent. Basal and lower cauline leaves are spathulate to oblanceolate, narrowed to a winged petiole, with entire or obscurely toothed margins; the upper leaves are sessile, smaller and progressively reduced. The capitula are solitary or few, radiate, with a hemispherical involucre of imbricate, herbaceous phyllaries in several rows. Ray florets are female, ligulate and lilac to bluish-violet, surrounding numerous yellow tubular disc florets. The achenes are compressed and pubescent, crowned by a pappus of barbellate bristles facilitating wind dispersal.
A member of the large and taxonomically intricate genus Aster, the species commemorates the Japanese botanist who collected extensively in the Himalaya, and it belongs to the assemblage of small Sino-Himalayan asters whose circumscription remains under revision following molecular reappraisal of the tribe Astereae. Its narrow known distribution along the Bhutan–Sikkim axis makes it of biogeographic interest as a regional endemic, and its conservation status is best regarded as data-deficient pending further field survey across the Eastern Himalayan high country.
Author: Kitam. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of China, Grierson & Long Asteraceae account, Monograph of Himalayan Aster