It is a herbaceous annual plant similar in appearance to many other mustards, growing an erect stem 15–100 cm (rarely 150 cm) tall. The leaves are lanceolate to elliptic, 2–11 cm long and 0.5–1 cm broad, with an entire to coarsely toothed margin. The flowers are bright yellow, 5–12 mm diameter, produced in an erect inflorescence. The fruit is a slender cylindrical capsule 1–3 cm (rarely 5 cm) long, containing several small, dark brown seeds.
It is widely naturalised outside of its native range, including in western and southern Europe, and North America.