With their show-stopping blooms and bursts of colour, dahlias are some of the most popular plants out there. But if you want to ensure your dahlias come back year after year, you need to know when to lift dahlia tubers.
Dahlias will suit any garden idea, no matter whether you’re opting for something soft and delicate or something punchy that will bowl you over with colour. And while knowing how to plant dahlia tubers is essential to growing these gorgeous blooms, knowing how to overwinter dahlias is also key to the survival of these tender perennials.
Like many other perennials, dahlias don’t cope well with the cold. Of course, there’s always a slim chance that they could survive the cold if left in the ground over winter, but it’s best not to take that risk. That’s why we’ve asked gardening experts when to lift dahlia tubers, so you know exactly when to start lifting.
What you'll need
If you don't have any cardboard boxes lying around, these flexi buckets will be perfect for storing your dahlia tubers over winter.
To lift your dahlia tubers, you'll need a trowel to hand. This is one of the best, and is extra strong in case your tubers are a little stubborn.
When storing your dahlia tubers over winter, you need to keep them warm and protected from the cold. So, you can cover them in compost.
Whether you’ve grown dahlias in pots or your garden borders, you should see that they start to fade as the daylight hours start to dwindle. And while it’s not uncommon for dahlias to continue to flower in October, they typically start to change in appearance at this time of year.
You may notice that the flowers start to fade, the foliage turns yellow, and the whole plant looks like it’s seen better days. When you spot these signs, you may feel inclined to lift the tubers immediately.
However, you should avoid lifting dahlia tubers too early, as they use this time between flowering and lifting to absorb and store nutrients that can then be used for bigger and brighter blooms next year. So, you need to wait a little bit.
You should only lift dahlia tubers after the first heavy frost of the year - which is typically during the first or second week of November, but can be sooner. This is echoed by Morris Hankinson, Managing Director of Hopes Grove Nurseries, who says, ‘Dahlias won’t survive intense frosts, so it is important to do this before heavy frosts.’
This frost will blacken the plants, and this change will signal you to add ‘lifting dahlia tubers’ to your list of garden jobs to do in November.
If you lift your dahlia tubers before the first frost of the year, you won’t harm these beautiful blooms in any way. They will be just as stunning as they were this year - but it’s worth noting that they may not grow any larger than they were this year, and you may find that your dahlia leaves turn yellow due to a lack of nutrients.
So, wait for the first frost before digging up the tubers, composting the spent foliage, giving the tubers a little clean, and then storing them over the winter in a frost-free location.
Morris adds, ‘Remove any dead, diseased or damaged material before drying out and storing in pots or containers with dry soil (it must be dry), sand, newspaper or vermiculite. Put them somewhere cool and dry where you can check on them every now and again over winter. It’s important they stay dry, or they could rot over winter.’
When the last frost has passed, you can then plant your tubers once again.
FAQs
Can I leave dahlia tubers in pots over winter?
If you have grown dahlias in pots, you have two choices. You could either lift your dahlia tubers to protect them over the winter months, or you could leave them in the pots and wait out the cold months in the hope that they survive.
However, you should always move dahlias in pots if you want them to survive the winter. Aim to move the pot into your house or to another frost-free area of your home or garden.
Ideally, store them in a warm garage or shed rather than a greenhouse, as you want them to be as warm and comfortable as possible.
How do you store dahlia tubers in an unheated garage?
If you have no choice but to store dahlia tubers in an unheated garage, there are some steps that you can take to ensure they stay as protected as possible. This includes covering them with compost, wood shavings, or even peat moss. You can also wrap them in newspaper and pack them in a cardboard box.
Unfortunately, despite these precautions, your dahlia tubers may still not survive an unheated garage. Keep your eyes peeled for tubers that look shrivelled or rotten every now and then.
So, there you have it. Now that you know when to lift dahlia tubers, you can wait until the perfect moment to start lifting.
