Most verbascums are short-lived perennials with saucer-liked flowers that are highly attractive to bees.
A particularly good variety is Verbascum bombyciferum, a vertical verbascum that is a summer sorbet of soft-lemon flowers and white swan's down, stretching up into the sky and often reaching over six feet in height. When the bee-friendly flowers fade, before producing their miniscule black seeds, the remaining multi-branched skeleton makes one of the most enduring autumn and winter silhouettes in the garden. Four or five randomly placed will give great long-term presence.
Where to plant
Verbascum should be planted in well-drained soil and sun.
How to grow from seed
Some varieties of verbascum are sterile and do not set seeds, while others, such as Verbascum bombyciferum, do.
Non-sterile verbascum such as Verbascum bombyciferum,can be left to self-seed on their own, which they do moderately. Or you can cut the spike and collect the seeds and dry them in the autumn.
Store them somewhere cool and dry until mid-spring and then sow them in seed compost (like John Innes no 1). They should germinate in 14 - 21 days and then the seedlings can be pricked out, once the true leaves appear, into individual three-and-a-half-inch pots..
Plant outside when the roots reach the bottom of the pot, usually in May, and leave the rosette to develop for the first year.
The flower spike will appear in the second year, but the plant will probably only live for 3 - 4 years in well-drained soil.
Alternatively Thompson & Morgan sell seeds labelled ‘Silver Lining’ or you can buy ready-grown plants from Beth. Other good seed strains include a short purple called ‘Violetta’) and a metre-high white called Verbascum hybridum ‘Snow Maiden’
Propagating sterile verbascums
Some verbascums have sterile flowers which do not set seed and these include the orange-brown ‘Helen Johnson’. These sterile forms have to be propagated from root cuttings taken in early winter, although you will have to dig up the plant. Look for thick, vigorous roots and cut away one or two and then replant the verbascum.
Get a tray of gritty compost and fill almost to the top and cut the root into sections measuring between 1 and 2 cm (half an inch).
Place them bottom down, top up into the compost and leave them to root. By early summer, the root cuttings should have produced some leaves and then these mini plants can be potted up. But patience is sometimes required as they can be slow to get going.
When to cut back
Most verbascums produce a large rosette and these can get shabby during winter. Tidy well in spring and then leave the plant to perform.
The stems are woody and most verbascums, even very tall ones, do not need staking.
There is a mullein moth which can eat the leaves and the large yellow and blue caterpillars can be a nuisance.
Having three or four verbascums in a sunny border of silver plants creates long-term presence. You could plant with lavenders, the billowing, later-flowering lavendins form large cloud-like mounds topped with slender long stems of tapering flowers. ‘Seal’ is excellent. Artemisias, anthemis and the herbaceous phlomis, P. russeliana, would also work.
The lemon-yellow flowers and white, downy stems of Verbascum bombyciferum are a fantastic foil for darker blues, purples and magentas - whether its penstemons, dahlias, hardy geraniums or roses.
Spikes are always good value as they produce masses of flowers without taking up lots of space on the ground and verticals help any border succeed visually as they lead the eye up to the sky and break up the boring hummocky look.