Getting dahlias through winter
Dahlias are among the loveliest of late-summer bulbs, flowering their socks off for weeks on end (especially if you dead-head them regularly to keep the blooms coming).
You can choose a dahlia to suit your garden whatever your style: spidery cactus varieties like 'Black Narcissus' for an exotic look, or pretty pompom 'David Howard' for a classic herbaceous border. Single-flowered dahlias suit natural planting styles: in our garden centre in London you'll find delicate pure white 'Twynings After Eight' and what are popularly known as 'The Bishops' – 'Bishop of Llandaff' in scarlet, yellow 'Bishop of York' or lilac 'Bishop of Leicester'.
All, however, are frost-tender, so need special care over winter.
In a well-drained soil in a warmer area of the country, you may be able to leave your dahlias in the ground: insure against hard frosts by covering the ground around the plant with a mulch up to 15cm thick of dry autumn leaves or coarse bark chips. Hold it in place with a double layer of fleece, pegged down to stop it blowing away. In spring remove the mulch to allow the plant to shoot up again.
If you're reluctant to risk losing your tubers in a hard winter, though, lift and store them in autumn under cover. Here's how:
- Once the foliage has been blackened by frost, dig up the tubers and let them dry for a day or so. Then brush off excess soil and trim back the stems to about 15cm above the roots.
- Line a shallow tray with newspaper and place your tubers on top with the stalks uppermost. Pack loosely with dry compost or sand, so the tubers are just covered.
- Store somewhere dry, cool and frost-free: a garden shed won't be reliably frost-free unless it's heated, so cover your dahlias with sheets of newspaper if a frost is forecast.
- Inspect your tubers regularly through the winter and get rid of any showing signs of rotting or disease, as otherwise it'll spread quickly to other healthy tubers in storage.
Please ask the staff in our London garden centre for more information and advice about storing dahlias over winter.