Eutrema scapiflorum

Description

Eutrema scapiflorum (Hook.f. & Thomson) Al-Shehbaz, G.Q.Hao & J.Quan Liu is a dwarf alpine crucifer of the high Sino-Himalaya, recorded from China, India, Nepal, Bhutan and Myanmar. The species is illustrated from Bhutan at approximately 4100 m, flowering in June, consistent with its occurrence in the upper alpine belt. It inhabits open stony slopes, moraines, fellfield, gravelly flushes and the margins of snow-fed rills, generally between 3800 and 5000 m, where it endures intense insolation, freezing nights and a compressed growing season. With around 630 GBIF records it is a genuinely high-elevation specialist, scarce and patchily distributed across its range.

The plant is a small, glabrous, cushion- to rosette-forming perennial arising from a stout caudex and taproot. The basal leaves are crowded, spathulate to oblong-obovate, entire or obscurely toothed, and rather fleshy. As the epithet scapiflorum implies, the white flowers are borne on short, nearly leafless scapes scarcely exceeding the foliage, each flower with four spreading petals and the typical cruciferous tetradynamous androecium. The fruit is a short, oblong to linear silique or silicle, somewhat flattened, dehiscing to release a few seeds in two rows.

The taxon was long placed in the segregate genus Pegaeophyton (as P. scapiflorum), reflected in its original webpage URL, but molecular phylogenetic analyses have shown Pegaeophyton to be nested within Eutrema, prompting the present transfer. It belongs to the tribe Eutremeae, a predominantly Himalayan and Central Asian lineage of cold-adapted mustards. Its restricted high-alpine niche renders it sensitive to upslope vegetation shifts and the retreat of late-lying snow, though no formal conservation assessment has yet been made.

Author: (Hook.f. & Thomson) Al-Shehbaz, G.Q.Hao & J.Quan Liu · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, Al-Shehbaz revisions of Himalayan Brassicaceae