Scree whitlow-grass

Draba glabella, the smooth draba or rock whitlow-grass, is a small, tufted, perennial herb of the Brassicaceae growing 5-30 cm tall from a stout, branched caudex topped by basal rosettes of leaves. Its range is circumboreal and arctic-alpine, spanning Greenland, Iceland, arctic and subarctic North America from Alaska to Labrador, south in the Rocky Mountains, and across northern Eurasia, where it inhabits calcareous cliffs, scree, gravel bars and tundra. The basal leaves are oblanceolate, 1-3 cm long, ciliate on the margins and clothed with simple, forked and stellate hairs; the few cauline leaves are smaller, sessile and sparsely toothed. Erect, sparsely hairy flowering stems bear a short, congested raceme of small white, four-petalled cruciform flowers 4-6 mm across that lengthens in fruit. The fruits are flattened, oblong-elliptic to lanceolate siliques 5-12 mm long, glabrous or nearly so, twisted at maturity and containing two rows of minute pale brown seeds. It is a variable, polyploid species often confused with related arctic drabas.