As the first frosts arrive, it’s time to lift dahlia tubers and put them in storage over winter, ready to replant next year.
Of course, some gardeners will leave the tubers in the ground – and keep their fingers crossed that we have a mild enough winter to keep these tender perennials going for another year, helping them along by cutting the spent plants down to ground level, applying a thick layer of mulch on the soil surface, and maybe even an upturned pot to stop persistent rain soaking and rotting the tubers.
But dahlias aren’t very adept at sustaining long periods of cold, wet or frosty weather – and if you live in a really cold, wet part of the country, you may be better off lifting them.
Here’s our step-by-step guide for how to do it…
1. Wait until the first frosts
Let the first frosts blacken the leaves to allow maximum time for the plant to make strong tubers. Then tidy up the plants by cutting back the stems to around 10cm (4in) high.
2. Label the plants
Tie a label to the shortened stem of each variety, so you can identify the varieties you’ll be replanting next year. Do it before you lift all the tubers, or it will become confusing.
3. Dig carefully
With a garden fork, dig around the perimeter of the plant to gently loosen the tubers. You do not want to be going in hell for leather and risking your fork damaging them. Lift the tuber out of the ground in one piece if you can, as bits that break off won’t regrow without an intact piece of crown and bud.
4. Clear off the soil
Remove soil around the tubers, which will be a piece of cake if you have sandy soil but trickier if you live on clay soil, in which case you may need a brush to help remove a lot of the caked-on dirt. Take care to hold the tuber by the main stems, so you don’t damage the crown or the clumps underneath.
5. Dry them off
Leave the tubers upside down in a greenhouse or shed to dry off, and once that’s done, remove any remaining soil with your hands and cut off any bits that look damaged or diseased. You can also cut back the stem by half again.
Put each tuber on newspaper, cover them with wood chips or compost, and wrap the paper around the tubers before placing them loosely in a cardboard box to store in a garage, shed or other frost-free but cool building.
Follow these steps, and hopefully they will be ready to be revived come spring for re-planting.