Lift or Leave? Deciding How to Overwinter Your Dahlias
The first proper frost has a way of focusing the mind. One morning your dahlias are still flowering, the next the foliage is black and limp. It’s the moment every dahlia grower asks the same question: do I dig them up, or can I leave them where they are?
There’s no single right answer. Plenty of gardeners leave their dahlias in the ground for years without a problem, while others lose the lot in one wet winter. It comes down to a few simple factors.
Why overwintering matters
Dahlias grow from tubers, which are fleshy, water-filled storage roots. They aren’t fully hardy. If the ground freezes deeply around them, or they sit in cold, waterlogged soil for weeks, they rot. Your job over winter is simply to keep them cool, dry enough and frost-free.
Leaving them in the ground may work if…
-
You garden in a milder area, such as the south and west of the UK, coastal gardens or towns and cities.
-
Your soil is free-draining and doesn’t hold puddles after heavy rain.
-
The bed is sheltered, for example against a south-facing wall.
-
You’re happy to take a small risk, and the varieties aren’t irreplaceable.
Lifting them is safer if…
-
You garden in a colder area, a frost pocket, or at altitude.
-
Your soil is heavy clay or stays wet through winter.
-
You have slugs in large numbers. They love the new shoots in spring.
-
The varieties are special, new to you, or hard to replace.
-
You want to divide tubers next spring to make more plants.
What about dahlias in pots?
Pots are the most vulnerable of all, because the compost can freeze right through. Either move the whole pot somewhere frost-free, such as a garage, shed or greenhouse, and keep the compost almost dry, or tip the plant out and store the tubers as you would lifted ones.
A middle way
If you can’t decide, hedge your bets. Lift your favourites and anything newly bought, and leave tough, well-established clumps in the ground under a thick mulch. Over a couple of winters you’ll learn what works in your own garden.
Coming up
Over the next few weeks we’ll walk through each option step by step: how to lift and dry tubers, how to store them safely until spring, and how to protect dahlias left in the ground.
Planning ahead for next summer? Browse our dahlia range in the shop and start your wish list now.