After a summer spent enjoying the blooms in our gardens, it’s time now to plan for the colder months and give perennials the best fighting chance of making a comeback next year.
Growing dahlias comes with its own challenges, as the plants grow from tubers, they have a certain sensitivity to the weather and the surrounding soil. That’s why many experts offer tips and tricks for keeping them alive over winter, especially when they’re planting in ground soil.
But how do dahlia tubers fare when they’re in pots over winter? We asked our gardening experts for their advice on whether you should unearth potted dahlias or leave them be.
Can you leave dahlias in pots over winter?
Overwintering is a great way to protect plants from frost in the winter and is an important step for many plant species. However, while you may know how to overwinter olive trees, the rules can be a little different for potted tubers like dahlias.
“Originating in Central America, dahlias are tender perennials which would be damaged if the ground around their tubers freezes,” explains Lucie Bradley, gardening expert at Easy Garden Irrigation. “However, unlike in garden beds or borders, where you would need to dig up the tubers and store them away over winter, when your dahlias are growing in pots, as long as you carry out several actions, leaving them in their pots can be successful.”
While you can certainly keep your dahlias in pots overwinter, there are some conditions you’ll need to meet.
“When overwintering your dahlias in pots, you need to keep the soil in the pot as dry as possible, so once your dahlias have finished flowering and as their foliage starts to change colour, you should reduce the amount of water you give them and stop watering as soon as the weather starts to turn cold,” instructs Lucie.
Newly germinated dahlia tuber in a pot
(Image credit: Getty Images)
Avoid making a winter gardening mistake by waiting too long to prepare for frost. Freezing temperatures can arrive pretty early during autumn, so it’s a good idea to think ahead.
“Wait until we have had our first hard frost in autumn, and the plants will have turned their energies away from producing blooms and into sending back energy to the tubers to store nutrients so they are strong and healthy for the following Spring,” starts Lucie.
“At this point, the foliage and stems will have changed to brown, and you can cut them back to be about 10cm above the surface of the soil so that they won’t be damaged by frost or rot,” she adds.
Lucie also recommends removing the first 2.5cm layer of soil to get rid of any pests and prevent them from hatching in your pot, where they’ll damage your dahlias.
“Move your pot with dahlias to a sheltered location where they will be kept frost-free – so that could be a garden shed, a garage or an insulated but unheated greenhouse. As a precaution – as any of these locations can still get very cold – always insulate the pot by wrapping the sides in bubble wrap, hessian or other material, tying in place with string,” she says.
Just make sure you’re checking the pots every few weeks to ensure they’re dry, and then they’ll be ready to be brought outdoors in late spring.
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Gardening Expert at Easy Garden Irrigation
With over 28 years working in the garden industry, Lucie has been fortunate enough to spend every day speaking to both amateur and professional gardeners. Encouraged to garden since she was old enough to walk, she believes that you can never know everything about gardening, as it is constantly evolving.
Do dahlias come back every year in the UK in pots?
Do dahlias come back every year in the UK in pots?
“Dahlias are tender perennials, which means they can come back every year in the UK if their tubers are not damaged by frost or rot. In pots, this is possible with the right overwintering care,” explains Chris Bonnett, gardening expert and owner of GardeningExpress.co.uk.
“Once you’ve cut your dahlia back, you can either keep the whole pot in a dry and frost-free place or lift the tubers out and store them separately. Either method can work well as long as the tubers are kept dry and protected from freezing temperatures,” he adds.
Chris is the founder of the online garden centre GardeningExpress and has been in the horticulture industry for over 20 years. Whilst he was young he combined his passion for the outdoors with the internet to deliver quality plants across the UK and Europe.
FAQs
How to cut back dahlias for winter in pots?
(Image credit: Getty Images)
Deadheading dahlias is a great way to help them keep blooming throughout the warmer seasons; however, cutting them back for winter is a little different.
“When cutting back your potted dahlias, always use a clean, sharp pair of secateurs and make a straight cut through the stems rather than a diagonal cut, which could allow water to collect inside the hollow stem,” recommends Lucie.
“You will even find some gardeners using a piece of foil to cover the top of the stem to prevent moisture from entering and causing rot,” she continues.
Just remember to always have your secateurs, an essential gardening tool, as clean as possible, so as not to spread any disease.
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How do you save dahlias for next year?
Should dahlias be one of your favourite cutting garden flowers, you’ll want to know how to save them for the next flowering season.
“To save your dahlias for the following year, dig up the tubers and clean them up with a gentle brush before storing them somewhere dark, frost-free and dry. Once they are dry, you can cover them with some dry compost, which acts as an insulating mulch,” says Chris.
“Check on them occasionally through the winter for signs of rot and remove any bad ones to prevent them from spreading. Store the tubers until you can plant them in early spring,” he continues.
Aside from frost protection, it’s also important to know how to protect your garden from heavy rain. Especially if you want to keep your dahlia tubers in their pots, you’ll need to keep the moisture and rain away from them, as the experts explain.
