These are plants that grow from seed in their first year, flower and set seed in the second year and then die. Actually, many biennials can carry on for another year or so, but they are often quite poor in subsequent years and so are usually pulled up by gardeners after flowering.
Wallflowers (Cheiranthus or Erysimum as they are now called) are one example of this. Some Erysimum, such as Bowles Mauve, can flower for a number of years, although they do have a tendency to develop woody stems and become a bit scruffy. If you take cuttings in summer then you can keep the plant going for much longer.
I have just bought a new Erysimum from a local nursery, which is an un–named red flowering plant, but I am assured that it is reliably perennial, so we’ll see.
Other perennial wallflowers are; ‘Bloody Warrior’ which is a dark red, and Bredon which has yellow flowers. These are quite difficult to find, so it is probably best to stick to the traditional biennial varieties.
I grow Erysimum cheiri ‘Blood Red’, ‘Vulcan’, which is dark crimson/maroon,’ Ivory Giant’ which is creamy lemon, and the orange Siberian wallflower, which I will not grow again as I dislike the colour – shame as it flowers for ages. These are all about 18 – 24”, although the Siberian variety is a little shorter.
They can grow in quite cramped conditions, hence the name ‘wallflower’ and like a sunny site, preferably with some lime. If you have an acid soil you can always sprinkle some lime into the planting hole when transplanting.
If you plant to grow your own Wallflowers, you can start them off now by sowing in a special nursery bed in the garden. Once they are a few inches tall, replant so they are about two inches apart. It is a good idea to ‘pinch out’ the top of the stems so that you start to produce a bushy plant. In September you can transplant them to their final positions.
Alternatively you can sow the seeds in plastic gutters or in divided seed trays, and then transplant them into the garden when they are ready to plant out in September.
The plants stay green all through the winter and will flower next spring, hopefully to coincide with your tulips flowering. Grow in drifts if possible as they look much better grown this way, and enjoy their scent and colour next spring.
Remember that wallflowers are of the Brassica family – like cabbage – so be careful if you have club root in the garden as the wallflowers can be infected.
You can buy seeds from most of the seed companies. If you are happy with a mixture then these are perfectly good, or you may prefer to grow single colours. Look out for the eventual height of the wallflower — I like to grow the taller ones so that I can cut the flowers for the house, but you can also buy shorter plants for ‘bedding’ out. These won’t be as floppy as the taller varieties, but they can look a bit ‘regimental’ when planted out – you pays your money and you takes your choice!!
If you don’t want to grow your own, try to buy healthy, bushy plants from a reputable supplier in Autumn to plant out ready for next year.