Hoary mustard

Hirschfeldia incana, the hoary mustard or shortpod mustard, is an erect biennial or short-lived perennial herb in the family Brassicaceae native to the Mediterranean basin and now widely naturalized across temperate and subtropical regions worldwide, including California, the southwestern United States, Australia, and southern Africa. Plants reach 30-150 cm in height, with stiff branching stems arising from a stout taproot and a basal rosette of leaves; the lower stem and rosette are densely clothed in stiff white spreading hairs, giving the plant a greyish or hoary appearance. Basal leaves are oblanceolate, 8-25 cm long, lyrate-pinnatifid with a large terminal lobe and several smaller lateral lobes; upper stem leaves are smaller, lanceolate, and entire to coarsely toothed, with a short petiole. The inflorescence is an elongate raceme of small four-petalled bright-yellow flowers 5-8 mm across, typical of the cabbage family. As fruiting proceeds the silique becomes distinctively two-segmented: a short lower cylindrical segment 4-12 mm long containing several seeds, and a much shorter, swollen, club-shaped upper segment with one or two seeds and a stout apical beak. The whole fruit is closely appressed to the rachis. The species inhabits roadside verges, fallow fields, waste ground, and overgrazed pasture.