A genus of annual to perennial herbs which have tap roots and erect, branched stems. The flowers are usually yellow and are always four-petalled, the elongated fruit having a lower part (containing several seeds) that opens by 2 valves each with one strong vein, and an upper, indehiscent part (the beak) with 0–3 seeds. Several are important vegetables (cabbage, turnip, etc.) or sources of useful oil (rape, black mustard, etc.). There are about 30 species, whose distribution is centred on the Mediterranean.
Subjects: Plant Sciences and Forestry.