Harry Sm.
Description
Saxifraga serrula is a high-alpine saxifrage of the eastern Himalaya, documented from Nepal, Bhutan and northern Myanmar, with a small body of records (c. 12 in GBIF) reflecting both its restricted range and the remoteness of its terrain. It is a plant of the upper alpine zone, growing among damp rock crevices, on moist screes, turfy ledges and seepage slopes, generally between about 3500 and 4500 m. The photographed individual from Tumching-La in Bhutan, at 3900 m and still in flower in October, exemplifies its tolerance of late-season cold at the margins of the snowbed environment.
The species is a small, perennial, cushion- or rosette-forming herb arising from a branched caudex, the foliage frequently forming low, compact tufts. The leaves are crowded in basal rosettes, oblanceolate to spathulate, and conspicuously serrate to serrulate along the margins—a feature reflected in the epithet—often somewhat fleshy and glabrous to sparsely glandular. The flowering stems are short and few-flowered, bearing actinomorphic flowers with five free, spreading petals (yellow to cream, sometimes red-dotted), five sepals, ten stamens, and a semi-inferior to inferior ovary of two carpels. The fruit is a many-seeded capsule dehiscing between the persistent styles.
Saxifraga is a very large, predominantly arctic-alpine genus, and the Sino-Himalayan region is one of its principal centres of diversification, with numerous narrowly endemic species concentrated in sections adapted to high elevations. Saxifraga serrula belongs to this radiation of eastern Himalayan alpines. Its narrow distribution and specialised habitat make it potentially vulnerable to climate-driven upward shifts of the alpine zone, although it has not been formally assessed; populations appear naturally fragmented across isolated high passes and ridges.
Author: Harry Sm. · Sources: POWO (Kew), GBIF, Flora of Bhutan, Flora of Nepal, Saxifrages of the World (Webb & Gornall)