Name also: Tall Rocket, Tall Tumblemustard, Jim Hill Mustard, Tall Mustard
Growing form: Annual herb.
Height: 30–80 cm (12–32 in.). Stem spreading from base, branched, sparsely hairy, lower part coarsely hairy. Rigid and leafless when old.
Flower: Corolla regular (actinomorphic), pale yellow, approx. 1 cm (0.4 in.), across; petals four, 5–8 mm (0.2–0.32 in.) long. Sepals 4. Stamens usually 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence an elongating raceme in fruiting stage.
Leaves: Alternate. Blade deeply pinnately lobed, with toothed margin, lower leaves broadly lobed, upper leaves narrowly lobed (lobes linear).
Fruit: Many-seeded, opens lengthwise, 7–10 cm (2.8–4 in.) long, round, often slightly curved, rigid, spreading siliqua, terminated by a usually approx. 0.5 mm (0.02) bristle. Stalk 5–10 mm (0.2–0.4 in.) long, as thick as siliqua.
Habitat: Wasteland, heaps of earth, roadsides, railways, harbours, factory- and loading areas, rubbish tips, sea shores.
Flowering time: July–September.