W.W.Sm.
Description
Primula tsariensis is an alpine perennial endemic to the eastern Himalaya, with a distribution centred on the borderlands of Bhutan, southern Xizang (Tibet) and adjacent NE India, and recorded from Sikkim, where the photographed plant was found near the Lada-La pass at about 3,900 m in June. GBIF documents this distribution across Bhutan (BT), China (CN) and India (IN) on the basis of roughly 67 occurrence records. It is a plant of the upper alpine zone, frequenting moist turf, scree margins and seepage slopes among dwarf rhododendron, typically between 3,800 and 4,500 m.
The species forms a small rosette-forming herb arising from a short rhizome with fibrous roots. The leaves are oblanceolate to spathulate, narrowed to a winged petiole, with a crenate to denticulate margin and an efarinose to thinly farinose surface. The slender scape bears a terminal umbel of few flowers; the calyx is tubular-campanulate and divided into narrow lobes, while the corolla is violet to purple-blue with a paler or yellowish eye, the limb of five obcordate, emarginate lobes spreading from a narrow tube. The species is heterostylous, producing pin and thrum forms, and the fruit is a small capsule shorter than or equalling the persistent calyx, dehiscing to release numerous angular seeds.
Primula tsariensis belongs to the section Petiolares, a complex and taxonomically intricate assemblage of Sino-Himalayan primulas distinguished by their farinose tissues and early-spring flowering close to the receding snow. Its narrow range across the Assam Himalaya and southern Tibet makes it a useful biogeographic marker of this high-rainfall sector. Although not formally assessed as threatened, such localised alpine endemics are inherently vulnerable to climate-driven upward shifts of the snowline and to habitat disturbance from grazing.
Author: W.W.Sm. · Sources: POWO (Kew), Flora of China Vol. 15, Flora of Bhutan Vol. 2, GBIF, John Richards: Primula (2003)