It’s the annual dahlia dilemma: flower farmer Charlotte Tombs looks at the pros and cons of different ways to protect your tubers from a frosty fate
Charlotte Tombs
What shall I do with my dahlia tubers? Do I leave them in? Do I dig them up and store them over winter? As with life, there are no easy answers, and pros and cons to both methods.
Dahlias are from Mexico – the tubers help feed them, but the tuber is fleshy and can rot or freeze. I like to think of them as tender perennials; with the right care they will come back year after year.
Coming from Mexico they don’t like continual freezing temperatures – they will rot very quickly if they are left to sit in water or those fleshy tubers are touched by frost.
The pros of lifting
By lifting dahlia tubers, you can check them over for disease. You can also firmly compost that one which was sold to you as ‘palest apricot with a hint of peach’ but actually turned out to be the most hideous yellow. Do that now; you’ll only forget and then regret it when it flowers next summer!
Split the tubers when you lift them and you make more plants for free – how is that not a win win situation?
You’ll know by early spring if the tubers have survived, giving you time to replace them with new dahlias.
You can plant them somewhere different each year, trying new areas.
The cons of lifting
It’s time-consuming to lift if you have lots of dahlia tubers!
Lifting isn’t risk-free: the tubers need to be properly stored or they’ll rot. They also need to be kept somewhere frost-free, and checked every so often. But if they’re kept too dry and warm, they can dry out completely, never recover … and still die.
The pros of leaving
You don’t have the hard work and worry of storing them correctly. All you need to do is add a thick layer of mulch over them.
Tubers left in the ground will start to sprout sooner, flower earlier, and have even more flowers as the tuber hasn’t been disturbed.
The cons of leaving
They will rot if they have not been sufficiently mulched or left to sit in water.
You won’t know if they have survived the winter until they start to sprout again. If they have rotted, you may find it hard to replace them.
Hedge your bets?
So whether you lift or leave your dahlias, there is a risk of losing them if you don’t do it correctly.
What do I do?
I hedge my bets!
I lift some, but I do leave the lion’s share in the ground – meaning I lost a lot of varieties last winter, as it was a particularly harsh one.
I am in a frost pocket, but I have free draining soil and I put down a thick layer of mulch after we’ve had two frosts, which will put the dahlias into dormancy. I also over-plant with my ranunculus corms once they are sturdy plants and these have a low tunnel over them, which also helps to protect the dormant dahlia tubers.
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