Don’t dig up dahlias for winter! What to do instead….
I don’t dig up dahlias to store them at the end of the summer.
And before you dig your dahlias up, it’s important to know the pros and cons.
You should dig up dahlias if your ground gets very cold and wet. If your weather is often dry, your soil is well drained and/or your winters rarely go below minus 6C/21F, then it’s worth leaving your dahlias in the ground.
Because even if you do dig your dahlias up and store them, there’s no guarantee that they’ll survive the winter. The autumn of 2022 was unusually wet in the UK. Many people, including professional dahlia growers, dug up their dahlias in very wet weather. They discovered that it was almost impossible to get them dry enough to store safely. A huge number of dahlia tubers rotted away in storage.
Yet many of the dahlias I’ve left in the ground, year after year, have filled our late-summer borders with glorious colour.
Although, perhaps the borders are not exactly the colours I originally planted. But more of that later.
As soon as people see the late-summer border, they ask two questions. The first is always ‘do you dig dahlias up for winter?’
Dahlias come from Mexico, which has warmer winters than most of northern Europe. So ‘dig up your dahlias for winter’ became standard advice for professional gardeners. However, professional gardeners are often working in gardens which have space for storage. And they usually have the skills to store the dahlias correctly, although the autumn of 2022 defeated many dahlia lovers.
But we’re a bit short of storage here, and my over-wintering expertise isn’t up to much either.
So this post is about middle-sized garden tactics, not ‘proper gardening.’
If you prefer seeing a video to reading a post, see this video on the Middlesized Garden YouTube channel here.
But your weather is important
Here in South East England, we have relatively mild winters. It would be very rare to go below minus 6C/21F, and average winter temperatures range between 3C-8C/37F-46F. And relatively speaking, it’s not too rainy, with between 1″ and 7″ of rain a month in the winter.
Dahlias don’t like having cold, wet roots, so if your garden is wet in winter, your dahlias are less likely to survive.
There can sometimes be pockets where dahlias will survive in much colder gardens than mine. I’ve received hundreds of comments on my video ‘Don’t Dig Up Your Dahlias’. Many are from people in colder climates, saying that their dahlias had survived in the ground over winter.
Very often there’s something that protects the dahlias, such as being planted very close to the wall of a house. The heat from the house can prevent the ground near it from freezing.
So it’s a question of trial and error. Generally, the colder and wetter your winters are, the less likely it is that dahlias will survive in the ground.
See this advice if you do need to lift and store your dahlias in winter.
And you can always treat dahlias as annuals, as many people who live in colder climates do. There is nothing wrong with buying your dahlias from new every year, and it gives you the option to change the colour scheme. One plant will cost you less than a bunch of flowers and will give you months of blooms.
How not to dig up dahlias
Firstly cut away the dead and dying foliage. I find some of my dahlia stems are so thick, they need loppers not just secateurs. (I particularly like Wilkinsons Ultralight Loppers, because they really are so light.)
Note: links to Amazon in this post are affiliate links, which means I may get a fee if you buy through them, but it won’t affect the price you pay. I’ve only linked to products I’ve tried myself and liked.
Once you’ve taken away all the vegetation, cover the dahlia with as big a mound of compost or mulch as you can. Pile it on, making sure that the stems are well covered to protect the snow and rain getting in down the hollow parts.
Then add a stick to show you’ve got a dahlia there. It’s as simple as that.
But take your anti-slug precautions early
The second question people ask is how I keep the slugs and snails off the dahlias. As you can see, I co-exist with slugs and snails. But I prevent them from winning by starting the battle early.
Best tip: I got this from a friend in the RHS. Start taking your anti-slug and snail precautions in February. Don’t wait until you see snail damage. I use ferric phosphate slug pellets, which are certified for organic use,and are pet and wildlife friendly. There’s more about it in this Controlling Slugs & Snails post.
Take a handful and simply throw them across the border in February. Don’t try to make little piles around where you think the plant will be. A light sprinkling will help protect your dahlias.
Steven Edney is an award-winning head gardener and plant grower. His family have been growing dahlias for several generations. He doesn’t use chemicals when protecting his dahlias from slugs and snails. Find out how in how to keep dahlias free of earwigs, slugs and snails without chemicals.
Sometimes you do have to dig up dahlias…
I must admit one thing.
Not all dahlias survive the winter protected by mulch, so I have lost a few over the years. The colour scheme is now dominated by reds and oranges, although the beautiful peach ‘Henriette’ has come back three years in a row.
Dark red Rip City and Black Cat dahlias have proved hardy, and also the orange Dahlia David Howard. However, a few dahlias haven’t survived, no matter how much mulch I pile on top.
I have also found that over the years, dahlias occasionally change character when they’re left in the ground. I think that they sometimes cross-breed themselves naturally. This can be delightful – or you can end up with a dahlia you don’t like. Most of my dahlias have stayed true, but a few haven’t.
Other garden lovers who don’t dig up dahlias….
Update: since this post appeared, I’ve had many comments (see below) and on Twitter. Some people find that dahlias survive the cold under mulch, but struggle in wet or poorly drained soil.
Gardening writer Susie White, who gardens in Northumberland says that she leaves her dahlias in the ground successfully, in spite of being in a frost pocket. Her garden was featured on Gardeners World as an example of gardening in extreme temperatures! However, she does have well drained soil, and adds a deep mulch.
Blogger The Reckless Gardener also leave his dahlias in the ground, although his Cumbria garden is also in a frost pocket. ‘Glad to see another gardener being reckless, too….’
If you love dahlias and would like to know more about them, Naomi Slade has written a glorious book about them called Dahlias – Beautiful Varieties for Home and Garden, with photography by Georgianna Lane.
The secrets of growing dahlias…from an expert!
Steven Edney, award-winning former head gardener of The Salutation Hotel & Gardens, comes from a family of professional dahlia growers. For his advice on how to choose dahlias, how to plant dahlias and what to do about slugs and snails, see this blogpost on growing dahlias.
Winter gardening – how to have a beautiful garden in winter
Whether you dig your dahlias up or not, they have no presence in the garden in winter. So you will want to find alternatives.
Evergreen shrubs and trees are at the heart of a winter garden. They’re also surprisingly low maintenance, as you usually only have to prune or clip them once or twice a year, then do nothing else. There’s a beautiful evergreen garden here, created out of common garden shrubs, but it has a real touch of grandeur.
Topiary creates interest in a winter garden, so here are some easy topiary shapes to add style to your garden. The most popular shrub for topiary is box, but there are huge problems with box tree moth caterpillar and box blight. See this post for three good alternatives to box.
Some conifers also have a bad reputation, but there is a huge range of conifers with different shapes, textures and colours of foliage. If you buy the smaller ones, they can really add to your garden all year round. Here is some advice on choosing conifers.
You can add a real splash of colour to your garden in winter with pots and window boxes. In these posts, garden designer Jane Beedle explains why you need to add more plants to winter window boxes and winter pots.
If we have a very harsh winter – or a sudden bout of bad weather, you may find some of your trees and plants looking quite damaged. But don’t cut them back immediately. Follow this advice on what to do for winter damage to shrubs.
And finally, of course, winter is a time when we often want to take a break from gardening. Don’t feel guilty about not following all the gardening ‘to-do’ lists. See this post on what NOT to worry about in the winter garden!
More good gardening resources
Do subscribe to the Middlesized Garden blog or YouTube channel for tips and inspiration from middle-sized gardens for other middle-sized (and small) gardens. And let me know if there’s any gardening job, you’d like not to do, and I’ll try to find out how not to do it.
(Although Anne Wareham is pretty good at not doing gardening in her book The Deckchair Gardener)
And I’m often asked for recommendations, so I’ve put together some useful lists of my favourite garden tools, books and garden products on the Middlesized Garden Amazon store.
And, although I wouldn’t wholly describe myself as an organic gardener, I do try to garden in a sustainable and wildlife-friendly way. So I’m delighted to partner with Teemill, a company with a similar philosophy, to create the Middlesized Garden t-shirts, hoodies and tote bags. The t-shirts and hoodie quickly became my wardrobe favourites, and they are made of natural materials, manufactured with renewable energy and delivered in plastic-free packaging.
Pin to remember dahlia tips:
And if you’d like to know more about the best plants for beautiful borders, see 6 perennial flowers that bloom all summer here. There are some wonderful tips on how to make a garden border look amazing here. And don’t miss the expert tips on how to plan a herbaceous border here.