Loved for their multi-petalled spheres, dahlias bring beautiful colour to borders and containers from summer into autumn. But do you know what to do with dahlias once the flowers begin to fade?
From deadheading spent blooms to deciding whether to lift and store the tubers, here’s what to do with dahlias once they've finished flowering.
1. Deadhead spent flowers
The first job is to deadhead regularly while the plant is still flowering to prolong its appearance in your garden.
'The fresh buds are usually round, whereas dead flower heads tend to be more pointed,' says Richard Barker, horticultural expert and commercial director of LBS Horticulture. 'Removing the whole flowering stem rather than just the flower head helps encourage the plant to produce more blooms.'
Make sure to cut the stem back to where it joins another stem or a set of leaves, taking care not to remove any developing flower buds.
2. Decide whether to leave the tubers in the ground
Dahlia tubers can technically be left in the ground over winter, but this can be risky in the UK.
'Tubers can be left in the ground to return in spring, but in the UK they are often too tender to survive through the winter,' says Richard. 'In some southern areas you may be able to leave them in the ground if winters are milder.'
If you do live somewhere with relatively mild winters, cut back the stems once the foliage has died and apply a thick layer of mulch around the base of the plant to help protect the tubers from frost.
3. Lift and store dahlia tubers
For most gardeners, lifting and storing dahlia tubers is the safest option if you want to enjoy the same ones again next year.
'Due to this, it is best to dig up and store tubers until they can be replanted in May after the risk of frost has passed,' says Richard. 'After the foliage has started to die back, carefully dig around the clump using a garden fork, taking care not to pierce or damage the tubers.'
Gently lift them from the soil and shake off as much excess compost or soil as possible. Then, cut down the remaining stems and thoroughly rinse the tubers to remove any soil. Turn them upside down somewhere dry to allow excess moisture to drain away and the tubers to dry completely.
4. Store tubers somewhere dry and frost-free
Once the tubers are completely dry, they can be packed away ready for the following growing season.
'Pack them into a box and cover them with dry compost,' says Richard. 'Alternatively, they can be stored in vermiculite or wrapped in newspaper.' The most important thing is to keep the tubers somewhere cool, dry and frost-free throughout winter.
A dry shed or garage can work well, provided temperatures don't drop below freezing. Check the tubers occasionally and remove any that show signs of rot, as this can spread to healthy sections. Once spring arrives and the risk of frost has passed, the stored tubers can be replanted, ready for another season of colourful dahlias.
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