Engl. & Irmsch.
Description
Saxifraga subsessiliflora is a high-alpine cushion saxifrage distributed across the Himalaya and the mountains of south-western China, with records from Bhutan, Nepal, northern India and China; herbarium material is also held in European collections such as Germany. The roughly 29 georeferenced gatherings place it firmly in the upper alpine to subnival zone. The collections cited in the image caption, from the Ludlow-Sherriff Trail at Warrtlang-La in Bhutan at 4500 m in June and from Kagmara-La in West Nepal at 4900 m in July, are characteristic, the species favouring rock crevices, stony moraine, scree and gritty alpine turf at roughly 4000-5300 m.
It forms low compact tufts or loose mats of densely leafy shoots. The leaves are small, oblong to spathulate, often somewhat fleshy and frequently lime-encrusted through hydathodes at the margins, the older leaves persisting as marcescent remains around the stem base. The flowering stems are short and few-flowered, so that the flowers appear almost sessile among the leaves, as the epithet subsessiliflora indicates. Each flower has five free, ovate, usually pale yellow to cream petals, ten stamens and a semi-inferior ovary of two carpels, the fruit a small bilocular capsule opening between the divergent styles to shed numerous minute seeds.
The species belongs to the large and taxonomically intricate genus Saxifraga, which is exceptionally diversified in the Sino-Himalayan alpine flora, and falls among the encrusted, lime-secreting alpine sections allied to section Porphyrion. Its cushion habit, reduced inflorescence and lime-encrusted leaves are convergent adaptations to cold, wind-exposed, high-radiation subnival environments. Pollination is by generalist alpine flies and small bees during the brief monsoon window. No formal conservation assessment exists, but its narrow high-elevation niche makes it sensitive to alpine warming and habitat loss at the upper limits of plant life.
Author: Engl. & Irmsch. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Saxifrages of the World (Webb & Gornall)