Erysimum syn. Cheiranthus. Often listed as Cheiranthus, but RHS classified as Erysimum. Many types can be grown as perennials, but most are best grown as biennials. They tend to become woody after a couple of years, and types like E. 'Bowles' mauve var. can be easily propagated from cuttings to produce more vigorous young plants. Others are best grown from seeds planted around August for the following year. there are lots of varieties in addition to the defined species. I have planted these as separate groups, but it is probable that some would benefit from planting as mixed groups, for example Ivory White and Charity Rose Red; but bear in mind the differing heights.
POD Plants of Distinction
CS Chiltern Seeds
Cheiranthus (Erysimum) cheiri vars.
Charity Rose Red (POD) 'frost hardy perennial'
The first year these grew in a rather weak straggly form, but it is possible that they were not in a good planting environment, rather dry under a tree. They are quite short, only about 15cm, and in common with many wallflowers have a distinct smell. Colour is dark pink/maroon, not rose red in my garden!
Cloth of Gold (CS) biennial
These were the most vigorous of the types I tried. Height was up to 45cm, with large spikes of bright yellow flowers. Easiest to grow and a good showing for several weeks.
Ivory White (CS) biennial
A nice lemon yellow bud opening to a creamy white. Healthy growth up to about 30cm.
Treasure Red F1 (POD)
Compact growth to about 20cm. Mine were not red, but a sort of mottled orange-brown, seemingly a more traditional sort of wallflower colour. But perhaps the packet was wrongly labelled-not an uncommon problem in my experience!
E. 'Bowles' Mauve' perennial
Grown from cuttings taken after flowering. Forms a bushy (eventually) tall plant that can be retained for many years. I find that they are less woody and look better if regularly grown from fresh cuttings.
E. linifolium 'Variegatum' syn. 'Sissinghurst Variegated'
Small and bushy, again best propagated from cuttings. Smaller mauve flowers than Bowles, variegated narrow leaves.
E. x Allionii (CS) Siberian Wallflower
Open growth to about 25 cm. Nice bright orange flowers