Hoary alison

Berteroa incana (hoary alison, hoary alyssum) is a biennial, occasionally annual or short-lived perennial herb of the mustard family (Brassicaceae), producing one or more upright, branching stems usually 30–80 cm tall and sometimes exceeding 1 m. The entire plant is densely covered with flattened, star-shaped (stellate) and simple hairs that give the foliage a distinctly grey-green, hoary appearance. The basal leaves form a rosette 8–10 cm long and are oblong-lanceolate with shallowly toothed or entire margins; the alternate stem leaves are narrower and sessile. From late spring to autumn the stems terminate in dense elongating racemes of small white four-petalled cruciferous flowers, each petal about 5 mm long and deeply notched into two lobes. The fruit is a small, hairy, inflated, elliptical silicle up to about 1 cm long topped with a persistent style and containing several reddish-brown winged seeds. Native to Eurasia, it is widely introduced and naturalised in western Europe and North America, thriving on poor, dry, sandy, gravelly, and alkaline soils in roadsides, pastures, and waste ground.