(W.W.Sm.) H.Hara
Description
Eutrema heterophyllum is an alpine crucifer of the high mountains of central Asia and the Himalaya, recorded from China, Nepal, Bhutan, Japan, Tajikistan and Kyrgyzstan, with GBIF logging 226 occurrences. It grows on open alpine slopes, damp gravelly flats, screes and the moist margins of glacial lakes and snowmelt rills. The photographed plant comes from Thitha Tso in Bhutan at about 4360 m, flowering in July, a cold, high-elevation lakeside habitat typical of the species' upper-alpine preference.
It is a small, glabrous perennial or biennial herb arising from a slender rootstock, with one or more ascending stems. As the epithet heterophyllum signals, the foliage is variable: basal leaves are often petiolate and entire to lobed, while the cauline leaves differ in shape and become smaller upward. The flowers are borne in a terminal raceme, small, with four white petals in the cruciferous cross arrangement and six tetradynamous stamens. The fruit is a slender, somewhat flattened silique containing the seeds in a single row.
The taxon is accepted, having been transferred to Eutrema by H. Hara from W.W. Smith's original placement. Eutrema, the genus of wasabi, has been substantially recircumscribed by molecular work that drew in numerous small alpine Sino-Himalayan species formerly scattered among other crucifer genera. As a cold-adapted, broadly distributed high-altitude herb it exemplifies the central-Asian alpine element of the Himalayan flora and is unlikely to be threatened, though dependent on intact periglacial habitats.
Author: (W.W.Sm.) H.Hara · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Al-Shehbaz's systematic studies of Brassicaceae