If you want a plant that flowers for a long time and is good for insects, Erysimum ‘Bowles’ Mauve’ is hard to beat. It is a bushy evergreen perennial which grows to 75cm (two and a half feet) to 90cm (three feet) tall and reaches a similar width. It has narrow, dark grey-green leaves and erect racemes of rich mauve flowers, which have a slight scent. (Watch a You Tube video about the plant.)
Wallflowers used in bedding schemes (also Erysimum) are usually treated as biennials and planted out in their first autumn to flower the following spring. However, they are actually short-lived perennials and I have some on the allotment that have lasted four years so far. They are becoming increasingly untidy with age but the flowers are still as lovely.
Erysimum ‘Bowle’s Mauve’ is a bit longer lived, though it won’t last more than a few years. It is hardly surprising – it must put so much of its energy into flowering. I bought the plant shown in the photo above last June and it has flowered continuously since then, including in the depths of our (admittedly very mild) winter. The flowers have attracted early bees such as Anthophora plumipes and have been visited by Large and Green-veined White butterflies.
To give your Erysimum the best chance of a longer life, grow it in well drained, poor to moderately fertile soil. (Our soil is rather sandy, so it is ideal). It won’t like soil that is too acidic or damp in winter and it likes full sun, preferably in a site that is sheltered from strong winds.
It is a good idea to remove dead flowerheads by cutting down a few leaves into the stem. If the plant ever stops flowering you can give it a trim all over to tidy it up. You can raise new plants from cuttings in spring to early summer. Pull off side shoots with a small ‘heel’ and, ideally, choose non-flowering shoots, though this is rather difficult with Erysimum ‘Bowle’s Mauve’!
If you enjoy growing this plant, there are other varieties of Erysimum too, such as ‘Apricot Delight‘ and ‘Walberton’s Fragrant Star‘. Many are scented, flower for long periods and are a real asset in the garden.
According to the Plants For a Future website, wallflowers contain various medicinal compounds but are not edible.