How We Lift and Store Dahlias for Winter
Lifting the Dahlias
We have completed the process of lifting all the dahlias from the beds, taking advantage of the recent dry spell. This same approach applies to dahlias grown in pots.
Timing and Frost Considerations
We do not wait for a frost before lifting dahlias, as we believe it is unnecessary. Neil, finds the task of cutting down blackened foliage after a frost to be quite unpleasant.
Cleaning and Preparing Tubers
There is no need to wash the tubers. The most important factor for successful overwintering is ensuring that the tubers remain dry. Leaving a little soil on the tubers can provide additional protection from the cold.
Checking for Disease
As we lift the tubers, we inspect them for signs of crown gall (Gal). The bacteria responsible for this disease are present in all soils, and because dahlias are not native to the UK, they have no natural defence. Infection usually occurs if a tuber has been damaged or has started to rot, often as a result of overwatering.
If a plant has grown and flowered well during the season, it was infected while in the ground. If you are uncertain about a tuber, simply store it separately. In spring, any affected plant will fail to grow properly, making it easy to identify and remove.
Drying and Labelling
We brush off the bulk of the soil and hang the tubers in the polytunnel for about a week to ten days, allowing them to dry thoroughly. Storing each tuber in its own labelled bag works well, as it keeps them separate and lets loose soil fall away.
Storing the Tubers
Once the tubers are dry, we place them in crates—there is no need for newspaper, sawdust, or straw. The crates can go in a shed, garage, or any unheated indoor space. Avoid using sheds with felt roofs, as these can become very hot even during winter days.
If there is a period of extreme cold (temperatures of -5°C or lower) or a prolonged cold snap, cover the crates with old blankets or towels to provide extra insulation.
Leaving Tubers in the Ground
If you prefer to leave dahlias in the ground, the key is to keep them as dry as possible. Winter rain is more likely to damage the tubers than cold temperatures. Soil retains warmth well into winter, and if tubers are planted at a depth of 10 cm or more, frost should not penetrate to that level.
For our field dahlias, we simply cut them down and place plastic lids on top to keep them dry. You can also use a plastic sheet, dustbin lid, or an upturned pot—just remember to weigh them down to prevent them from blowing away.
Spring Growth
The dahlias will come out of hibernation at the end of March or in early April. It is best not to start them too early in the new year, as dahlias can grow very quickly indoors and may become too large before they can be planted out after the last frosts in May. Early growth in low-light conditions can weaken the plants.
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