Bastard cress

Thlaspi arvense, the field penny-cress, is an erect annual herb of the family Brassicaceae growing 10 to 60 cm tall, with a smooth, often branched stem that smells unpleasant when bruised. The lower leaves form a rosette while the stem leaves are oblong, toothed and clasp the stem with arrow-shaped bases. The small flowers have four white petals and are clustered in elongating racemes. Its most distinctive feature is the fruit: a large, flat, rounded, broadly winged pod deeply notched at the top, resembling a coin or pennyworth, containing several dark, concentrically ridged seeds. It flowers from spring through summer. Native across Europe and Asia and widely naturalised, field penny-cress is a common weed of arable fields, gardens, roadsides and waste ground. The whole herb and seed are used in traditional Chinese medicine.