Arabidopsis lyrata

Arabidopsis lyrata, the lyre-leaved rock cress or sand cress, is a small biennial or short-lived perennial herb of the Brassicaceae with a circumboreal to temperate distribution across North America and Eurasia. Plants form a persistent basal rosette of pinnatifid or lyrate leaves 2-8 cm long with 2-5 pairs of small lateral lobes and a larger terminal lobe; rosette leaves are dull green and sparsely covered with simple and branched trichomes. From the rosette arise one or several slender, erect to ascending flowering stems 10-40 cm tall, bearing a few small, narrower, entire to slightly toothed cauline leaves. The inflorescence is an elongating raceme of small flowers; each flower has four white petals 5-9 mm long, four sepals about half as long, and six tetradynamous stamens. The fruit is a long, narrow, linear silique 1.5-4 cm long on a slender pedicel 5-15 mm long, dehiscing along two valves at maturity to release numerous small, brown, wingless seeds in one row per locule. The species grows on sandy, rocky and calcareous soils of cliffs, dunes, open woods and disturbed ground, and is widely used as a model in evolutionary and population genetics as a close relative of A. thaliana.