Brassicaceae: grey-green annual or biennial to 1.2, found by river banks, arable and waste land. The yellow four petalled flowers are up to 13mm across, blooming from May-September. Quite common across most of the country. Native to most of Europe, and very common around the Mediterranean. Naturalised in Britain.
The leaves can be eaten raw or cooked, they have a strong radish/cabbage flavour. An edible oil is obtained from the seed, it is best when cold pressed.
The tuberous roots and seeds are considered to have antiscorbutic properties. A rather strange report, the leaves are much more likely to contain reasonable quantities of vitamin C than the roots or seeds.
Succeeds in full sun in a well-drained fertile preferably alkaline soil. Sow seeds in spring or autumn in situ. Very Easy.