London rocket
Sisymbrium irio

Annual or biennial herb 25–60 cm high, glabrous or with long curved hairs.

Basal leaves not in a rosette, to 25 cm long, pinnatisect with 2–6 pairs of lobes, toothed, petiolate; upper leaves sometimes entire.

Inflorescence without bracts. Sepals c. 3 mm long, glabrous. Petals usually 2.5–4 mm long, yellow to pale yellow. Siliqua linear, spreading, 2.5–6.5 cm long, < 1 mm wide, with swollen portions, valves glabrous, thin-walled, ± translucent; pedicel slender, 6–10 mm long.