This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
This plant is found in the Channel Islands, in Jersey, Alderney, when native, but is a casual elsewhere, and is confined to Europe. It grows in sandy fields. The habit is branched or pyramidal from below upwards. The stem bears few divided leaves, with the leaflets, larger at the extremity below, lance-shaped above. The chief distinction between this and others lies in the short beak of the pod with one seed, the pod being pressed close to the stem. It flowers in July and August, and is biennial. The seed-coat swells when wetted, helping to fix the seed in the ground when germinating.
This Crucifer is found in most parts of the British Isles, and is distributed generally in Europe, parts of Asia, Africa, being in America only an introduction. The habitat is dry soil of a gravelly character, fields, waste places, and roadsides. The habit is erect. The stem is single, branched above only, with leaves of an arrow shape. The style between the paired valves is not longer than the notch, the pouch scaly, with a broad wing. The plant is as much as 1 1/2 ft. high. Flowers may be found in June up to August. It requires a sandy or gravelly soil. The flowers are not attractive to insects, being diminutive. The pods open when ripe, letting the seeds fall close to the plant, which grows in clumps. Like other members of this group condiments are prepared from it.