Although my Dahlias are still displaying a vibrant flowering, I sense that their days are now numbered.
This raises the perennial question of wintering dahlias: do we really need to dig them up? Where and how should we store them during winter?
Is it really necessary to dig up dahlias?
Well, it depends! Native to Mexico, Dahlias have frost sensitivity embedded in their genes and although they have acclimatised well here, their hardiness is not without limits. Therefore, to keep it simple, I would say that digging up Dahlias is, depending on the case, obligatory, prudent, or facultative.
An obligatory measure in cold climates
If you live in a region with harsh winters, where temperatures can regularly and persistently drop below -5 °C, digging them up is mandatory to avoid losing them all to frost. And although we have some splendid new varieties lined up for next spring, it would be a shame, wouldn’t it?
A prudent gesture in heavy soil
Dahlias are not only afraid of frost, they also dread moisture. In a mild but humid climate (you can’t have it all!), everything will go well as long as your soil is light, preferably sandy, or if they are planted on a mound or slope. However, in clay soil or in areas that are regularly waterlogged in winter, rot is a major risk. To avoid this, I strongly advise you to muster your courage (and your fork) with both hands!
An optional precaution in mild climates and well-drained soil
In well-drained soil and anywhere where frost is occasional and light, you can perfectly leave them in the ground, while protecting them with a thick layer of mulch, ideally made of dead leaves, straw, or dry materials (under no circumstances should it be under a layer of fresh grass!)
Digging up vs. leaving in the ground
Ultimately, it’s in mild regions that the decision to dig up or not dahlias is the most difficult to make.
To weigh the pros and cons, let’s examine the advantages of digging up and leaving in the ground.
Advantages of digging up
- Digging up dahlias is a change from potatoes 😉 and discovering huge tubers is simply exhilarating!
- Digging up dahlias allows for variety in creating new beds each year, by moving them around or associating them in different ways,
- Digging up allows you to divide the tubers (useful when you have a large garden or many friends), but also a potting up in March - April to achieve earlier flowering, as well as to protect them from the spring appetite of slugs
- In good conditions (frost-free, in a dark and well-ventilated place), dahlias store remarkably well, the risk of loss is close to zero.
Advantages of leaving in the ground
- Leaving dahlias in the ground means saving time and space, as cleaning, labelling, and storing different varieties is a task that requires some availability and suitable storage… which not all gardeners have!
- In the ground all year, your dahlias are undisturbed. And you won’t risk injuring them (an unfortunate fork mishap happens often) and they can continue to grow comfortably to form a lovely clump.
When and how to dig up dahlias? How to store them?
Every gardener has their habits regarding the best time to dig up dahlias. For some, the starting signal is the first fires in the fireplace, while for others it’s the first real frosts that blacken the foliage. Do as you see fit, the important thing is not to intervene too late!
As for the digging up itself, it’s a simple operation, summarised in this tutorial :
For storage, equip yourself with crates or boxes made of cardboard or plastic filled with straw, turf, or sand, labels, and a good felt pen... whose ink won’t fade in a few weeks.
As with your favourite wines, and failing to find a dahlia cellar on the market, choose your location wisely: it should be dark, frost-free, but not too warm and well-ventilated… This could be a basement or a not-too-damp cellar, or simply your garage.
Finally, remember to check on them regularly, as this is the best way to prevent any issues and ensure optimal storage!
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