The classic violet-purple sweet rocket, the form that has been filling English cottage gardens with evening scent for centuries. Loose clusters of four-petalled flowers on branching stems at 75 to 90cm.
It is worth understanding what it is for. As a daytime plant it is unremarkable and slightly coarse. As an evening plant it is one of the best things there is; the fragrance of violets and cloves comes up as the air cools and carries a surprising distance. If you have a seat you use after supper, put this behind it.
Biennial, so a rosette in year one and flowers in May and June of year two, then it dies having seeded generously. It will hold a colony indefinitely without further help, and it will also wander, so pull the seedlings you do not want.
It is a brassica, and that matters twice over. The orange tip butterfly lays on the flower buds and seed pods and its caterpillars feed there, so leave some standing rather than tidying it all away. And it gets mildew and flea beetle like any other brassica, particularly in a dry summer.
