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.
All these dahlias were planted between eight and three years ago. I have never dug any of them up to over-winter.
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?’
Our dahlia border
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.
This is Dahlia ‘Senior’s Hope’. It has survived two winters in my garden.
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.
You may not feel inclined to take my anti-snail advice, having seen this picture. But at least I enjoy my dahlias as much as the snails do.
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.
I’ve used several brands, such Bayer Garden Slug Killer and Sluggo
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.
This is Henriette. She is so pretty, and has come back every year for three years now, protected by a big pile of mulch.
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.
The dahlias that do come back seem extra vigorous, perhaps because of their nutritious mulch meal. This is ‘Con Amore’, with some ‘Rip City’ (the darker red).
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.
This dahlia seems to be a love child of some of the dahlias in the photo above it. I think it could be a blend of Con Amore and Rip City. This has only happened once in all my years of leaving dahlias in the ground, but if you discover an unexpected dahlia, then it may be that a new variant has popped up courtesy of the bees.
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.
Dahlia ‘Akita Explosion’
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.
Even if you don’t dig up your dahlias for winter, they will be underground until spring comes. So use evergreen shrubs and trees to give your garden winter interest.
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.
Our niece Irene in the ‘If at first you don’t succeed, plant, plant & plant again’ hoodie. Also available as an organic cotton t-shirt and a tote bag.
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.
Hi…could I cover my dahlias in winter with insulated tinfoil
Would I put it under the compost or over…..or could I use old pot plants with holes in them..thank you
If your dahlias survive covered in compost, that’s great, but if they don’t, I don’t think tin foil or pots would make much difference, and blocking the light could affect how they grow again in the spring. It’s worth looking at whether there are different parts of the garden where the dahlias survive over winter – in some cases a border near to the house would be warmer and drier than one further away. Good luck
My soil is thick clay, for many years I cut back my dahlias in November put plastic buckets over them until the frosts are over. Very rarely lose one.
Interesting!
I live in the Pacific Northwest where it rains a lot but the temperature in Western Washington rarely goes below 20 degrees F. but even so I’ve luck with some mulch and a black plastic cover that I cover my just chopped down stems in November with and remove by early May ( and promptly apply slug bait). Mostly the red ones survive but the blooms are becoming small but plentiful. Maybe some judicious pinching out?
I planted dahlias last year and was not happy where I planted them. They were too tall for where they were located (looked awkward). Is it okay to transplant them in the spring (I did not dig up the tubers in the fall). I live in northwest New Jersey.
Yes, transplant them in the spring, once the frosts are over.
Shame on you using a ” slug killer”….this will harm the birds! I feed birds all year round in my garden and have no slugs whatsoever! Beatrice, Co Wicklow, Ireland
Traditional slug pellets contain metaldehyde, which can harm birds, pets and wildlife generally. These are now banned in the UK (since 2021), and I have never used them, but they are widely available in Ireland, which is presumably why you are concerned. The organically approved slug killers I use (in very, very small quantities) don’t harm the birds or any other wildlife. Their active ingredient is ferric phosphate, which is a naturally occuring element. There is some evidence that adding too much ferric phosphate to the soil would harm earthworms, so I agree that the ideal is not to use a slug killer at all (or only to use it in pots, not in the earth). The full explanation of how I control slugs and snails on dahlias without using harmful chemicals is here /keep-dahlias-free-earwigs-slugs-snails-without-chemicals/
Hi! I left my dahlias in my barrels and pots over winter. what do you suggest I do now that spring is almost here? what kind of soil should I add? etc.. Thanks!
It would probably be best to take them out of the pots, replace the soil or potting compost and add some slow release fertiliser, then return the tubers to the pots. The pots need to stay in a frost-free place until the last frosts are over, but they’d appreciate as much light as you can give them.
I live in Canada where the winters are long and cold. I don’t have the space for dahlias but my mother loved them. We lived on a farm and we were too busy to dig up the dahlias every fall but they always came back every year.
That’s really interesting and you’re not the first person to say that their dahlias have come back in much colder places than you might expect.
Hello, I have seen an offer for some really cheap dahlia tubers (pennies) but as it’s mid-August, is it possible to store these over winter in their plastic bags, or will they not last? If not, can they be planted now or are they just not worth it?
Don’t store them in plastic bags because they can rot in plastic. If they’re really cheap, then it’s often worth taking a punt on it, but there are no guarantees. I’d suggest you store them in winter in a cool, dark, but frost-free place (a garage or shed is often best), wrapped in newspaper or hessian. Then take them out when the days start to lengthen (February, for example) and plant them up in pots, keeping them somewhere light and frost-free, with the soil just moist but not too damp. If you don’t have a cool, frost free place to store them, it’s probably best not to buy them and to buy new tubers in spring.
I saw three tubers for £3.99 on sale about a month ago and I couldn’t resist so I bought them and planted them out in a large pot. They all sprouted and now I’m just going to leave them outside with the older dahlias until the frost gets to them and treat them the same as the others ( mine are all in pots so I just take them into the garage in November after the first frost. It seems worth a try.
It’s always worth a try!
I have Dahlias is a ceramic pot on my patio in South London. How much mulch would I need to cover the tubers with? Would bark be OK? I would worry that any frost might penetrate through the pot?
The mulch is really only appropriate for dahlias in the ground. I suggest you protect your pot with the dahlia in it by pulling it as close to the house wall as possible, because the wall of a home holds some heat in winter and wrap the pot in something protective when the winter gets very cold. Bubble wrap, hessian sacking – anything that keeps the frost from the pot. The dahlia will not be growing over the winter, it goes dormant which means that you clear away the dead foliage and it will re-sprout next spring.
My dhalias are left in the ground and for the last few years have returned to bloom fantasically. Now it is mid May and so far no sign of them, does this mean they have died? I’m sure they are usually growing by now.
It’s difficult to say – if you’ve had an unusually wet winter, they may have rotted. Or they may yet come up. I hope they do.
So refreshing to see this! I really enjoy the laid back attitude!
Thank you. It doesn’t work for everyone but I’m amazed at the number of people in quite cold places who have commented that they left their dahlias in successfully.
This must be for warm climates? I can’t see how tubers would live in solid frozen winter ground.
It’s more about wet than about cold – there are a number of parts of the UK where dahlias are usually fine if left in. They wouldn’t want to be in very cold, damp or -as you say, frozen – soil, but it’s relatively rare for us to have long freezing spells in most of the UK now anyway (it’s unusual for our winters here to go below minus 6C/21F and they’re not even that low for very long). In terms of the US, this advice would work in most of zone 9, and quite a bit of zone 8, but I’ve had comments from people as low as zone 7, who have succeeded in keeping dahlias in the ground over winter. I imagine they must have some kind of micro-climate.
So if you live somewhere like Vermont or Canada, where you get months of snow and below freezing temperatures, then dahlias definitely wouldn’t survive. If you are in the UK, unless you have very boggy ground, then it’s worth a try, and if you’re in the drier parts of South East England, then you’ll probably be fine. Mine survived The Beast From the East, which was about two weeks of snow and ice.
I hope that helps,
I live in Kent and I to cut down then cover with cheap compost for the winter. I also have managed to get hold of a number of the large water dispenser plastic bottles, which I cut the bottom off and then use the bottle as a closh.
I live in Kent too and I agree it’s usually reasonably mild in the winter. I don’t think you have to use cloches, though, I haven’t come across any professional head gardeners who do, and I usually take my cue from them as they are gardening in a very practical way.
I too live in Kent and after cutting down the year’s growth I add some compost and then put a large upturned flowerpot over the site – thus it gets some rain but not too much. A similar idea to Tony Townsend.
Interesting. This will really be the year when we will see if we all need to do that as we had a very wet autumn followed by a cold snap, which dahlias will not have liked. Stored dahlias have suffered, but it’s too early yet to see if dahlias left in the ground survived.
I live in Kent too. I use some compost on the cut back dahlias and then put a large flowerpot over each clump. I think this mat prevent some of the winter rain which is the real enemy.
Hi, I have dahlias in a large above ground wooden planter, should I lift them or can I leave them in over the winter? I’m guessing they might not be as protected from cold and frost as they would if they were in the ground?
The important thing is to prevent them from getting immersed in cold, wet water over the winter, or freezing. So if the pot is in a sheltered place and drains well, it’s probably fine. I’d suggest wrapping a horticultural fleece, straw or hessian sacking around it when frost is forecast. If you get a lot of frost, though, I’d suggest taking them out of the planter, you’re right that they will be more exposed than they would be in the ground.
To really protect the dahlias over winter plant out the bed with daffodils. As the daffodil bulbs start into growth in the really cold weather they give off heat which protects the tubers and as soon as the daffodil leaves are above ground any snow that falls doesn’t reach the surface.Leave the daffodils after flowering until the end of May and cut them back to the surface when you will see the dahlia shoots beginning their growth. Cut the dahlias back in November right to the soil and cover with fresh compost to allow them to overwinter along with the daffodils. I’ve been doing this for over 20 years and have never lost a dahlia.It makes the gardening really easy with minimum intervention.
That’s an interesting tip, thank you.
Interesting, conversation – thank you. Should the mulch covering the dahlias be scraped back gently in spring, or will the new shoos happily grow through it?
The mulch will slowly break down as worms and microorganisms get to work, and it will feed the soil. The new shoots will happily grow through what remains of it.
Great, thank you
I always kill dahlias when I try to lift them, so last winter I left them in the ground. Cut them after frost hit, left them to dry for a week, then covered with leaves, used furnace filters, and some evergreen boughs. I am in zone 6b, but they’re along a south-facing wall and it’s pretty dry. Uncovered them when it warmed up, and almost all grew back, and twice as vigorous as last year.
I think you hold the record for dahlias surviving in a cold winter. Although as you say, a south facing wall and it’s pretty dry are both good.
Hi, This is my firo uear planting Dahlias and they thrived for months. I am in zone 7a. I originally was going to rip up all of the plants so I can plant my fall plants until I read this article. I would love to try to save them for next year but is there any way I can plan on top of them once I cut them back? I really wanted to plant some beautiful mums?
Zone 7a means quite cold winters, and there’s much less chance of dahlias surviving the winter. You can experiment and leave them in, but don’t be surprised if they don’t survive. You can’t plant on top of them once you have cut away the foliage. You’ll have to find a separate space to plant the chrysanthemums, although it may be getting a little late and cool for them too.
Hi Alexandra, and thank you for a very informative article ! I’ve just acquired a Rhino greenhouse, which has fantastic ventilation. Question – As my small garden is full of plants, can I grow dahlias in pots in the greenhouse all summer, maybe with the aid of a fan or two ? I’m in the cold and very winter wet Lancashire, on heavy clay.
I think you may mean ‘grow dahlias in the winter’ – you’ve said ‘grow dahlias in the summer’. You wouldn’t need to keep the dahlias in the greenhouse in the summer, you could grow them outside, although you could as they originate from Mexico so are happy with warmth. If you were thinking of growing dahlias in pots in the greenhouse in winter, they are dormant at that time so you wouldn’t get any flowers. I sometimes leave my dahlias in pots in the potting shed and they survive well, but they don’t have leaves or flowers. I hope that helps.
All my dahlias are in pots on my terrace in Soho, as its a terrace I dont have a shed or greenhouse so they’re left in the pots to overwinter and the majority spring back every spring..The ones I lose I’m never sure if its frost or due to vineweevils..which appear every so often to blight my life..
Oh, dear, I think it’s vine weevils – they are terrible once they get a hold.
I have left my dahlias in the ground the last couple of years, covering them with any mulching material to hand, and covering them with a cloche which I also add some insulating material to – I have used both straw and old bubble wrap with succes. I keep the vent in the top of the cloche closed, this ensures the dahlia tubers don’t suffer from excess moisture and reduces the rot risk.
I have a question tho, one of my dahlias has woken up and is now showing a very high number of shoots emerging. I wonder if this is a sign that I need to split the tubers ? Or should I just pinch away some of the shoots so things don’e get too crowded and I improve the strength and space for the remaining shoots ?
regards!
I think it’s probably time to divide the dahlias. This can be done either in spring or fall. I’ve found that dahlias which are happy to be left in the ground get very happy, which means they really spread.
I ask the question, when do Dallas start to shoot out doors if left in the ground over winter
Dahlias should come up around the beginning or middle of May, depending on what your climate is like.
Last year was my first year planting dahlias and I left them in the ground over winter. I live in zone 9B, and have heavy clay soil but very little rain at all year-round. It’s April and my hostas & peonies are growing again but I haven’t seen anything from the dahlias yet, should I be concerned? Should I begin to water them before they come up or wait till I see something growing? Anything else I should be doing?
My dahlias don’t usually emerge until May, so wait a while. It’s probably better not to water while they are still dormant, because if they’re not taking up the water, it may rot the roots. And there’s nothing else you can do. There’s always the possibility that they may have died but Zone 9b should be pretty safe (unless they’ve been eaten by something, although that’s even less likely) as your winters are even milder than ours. Good luck and I hope they emerge.
Hello! I live in Arizona, north of Phoenix, USDA zone 9b and elevation of 2500′. I have two dahlias in pots on my patio. I adore them and want to see them come back next spring. Can I just cut back foliage and move them to a dry, protected from frost spot on my patio? We do get an occasional frost over the winter. Thank you!
Yes, I’ve done that sometimes and it seems to be fine. Once you’ve cut back the foliage, move the pot to a dark, frost-free spot (maybe a garage?) then move them out into the sunshine and repot them, probably around March, depending on when your days lengthen and there is more sunshine. Then keep them protected from frost until your last frosts.
Thank you! I’m going to give this a try.
Hope it goes well!
Hi! I plan to leave my Dalhias in the ground this year. Can I just put leaves on top of them to protect them? Will that be enough. I have a lot of leaves!!
I would suggest adding some mulch, such as garden compost or well rotted manure. It’s very much a question of trying it out and seeing what works. Just leaves may be fine in your weather, but it’s hard to be definite.
Hi there I live in Staffs and have tried the leave in the ground method this year. Haven’t seen any sprouting yet though so I think I may have killed them..I covered them in compost but over the months the weather has eroded the pile so the tops are peaking out. Anyone had any sprout yet? Emma
It’s still a little early and we’re having quite a cold spring, so there is hope yet. It can depend on your micro-climate too, if you’re in a particularly frosty place, then they may not come back but if that border is, for example, near a house wall, then it may be warmer and more sheltered. But don’t despair until about the middle of May.
I live in California. Overnight temperatures are still below 50 and daytime between 68 and 80. I have a dozen dahlia shoots up with some up to 6 inches and doing great. Still waiting on another 50 out there. I dug down to see if one was still alive. Found the tuber and some buds on it. Was a bit deeper down than the others. So hopefully, we won’t lose that many. After trimming them back to 2 inch stems in November, I covered them with a black tarp so the sun would warm them earlier. We live in a zone 9 climate with winter temps only getting down to 30 degrees a few times. So far, so good.
Great, and those temperatures sound fine for overwintering dahlias, especially if you don’t have very wet soil. I don’t even cover with the tarp, although I do cover with a layer of garden compost or mulch, which helps protect the tubers and eventually breaks down and feeds the soil. But it’s all a question of trial and error and what works best for you.
I’m in Wolverhampton and some of mine left in the ground have only just started showing signs of life this week so don’t worry, there’s plenty of time yet
I have dahlias in a pots want to take your advice by cutting them back for next summer and leaving them in the pot. Can I do this. please advise
Yes, you can leave them in the pot (I have done this myself successfully) but make sure the pot is in a dry, dark, frost-free place. You could wrap it in horticultural fleece, and yes, do cut off the foliage before storing them for winter.
Hi I too want to leave mine in the pot but I was wondering if I could move them into the garage? If this is ok do I still cut them down and cover them?
Once the foliage has died back – that’s usually when the first frost arrives, cut off the foliage. Then you can take them into the garage (I presume your garage doesn’t freeze?) I usually wrap mine in some sort of insulation – such as hessian, sacking or horticultural fleece. The aim is to prevent the frost or freezing weather reaching the pot, so quite a lot depends on what your winters are like. If you live somewhere where there is several feet of snow for months on end, the garage may be too cold. But in an ordinary UK winter, the garage will usually be fine.
New to growing Dahlias – how did they fare in terms of ones you left in the ground over winter 18/19 as it was fairly mild in the UK. I am in South Wales so I will leave them in the ground and mulch deeply to see if I have any luck I have two of the bishops (York and Llandaff).
I left my dahlias in the ground over the 2017/18 winter, which was very harsh at various points. They did all come back although I think a few were less big than usual (ie one or two tubers may have died in a group of several). However, nothing stops certain varieties, for example ‘Orange Cushion’ which doesn’t let a harsh winter interrupt its play for world domination.
What growing zone do you live in?
The USDA growing zones don’t exactly correlate in the UK, because we have less difference between summer and winter due to the Gulf Stream, but here in South East England we roughly equate to a Zone 9 or 8b. I have had comments on this post and the accompanying YouTube video from people in colder zones who have left their dahlias in, but I suspect that they have a fairly dry climate (dahlias hate wet, cold soil) and also that they may have a particularly sheltered spot or microclimate. I’d say, give it a try but expect to lose some dahlias if you’re below a Zone 9.
I have bishops children surviving the winter here in the midlands in a sandy raised bed. It’s got down to minus 8 and they still pull through. I also don’t mulch them, probably that and the sandiness seems to keep the slugs off.
I’ve sometimes wondered if I lost my ‘Bishops’ not because of winter cold, but because I planted them in too a shady bed and they just didn’t like it. I’ve been told since that Bishops would be just as hardy, if not more so.
Is this still true for you? I too am in the midlands and just toying with the idea of leaving mine in the ground..
Yes, the dahlias that I left in the ground have mainly come back. It seems they either survive and really flourish or occasionally they don’t. I gather from other gardeners that it is not just about how cold your winters get, but how wet, as Dahlias don’t like to sit in cold, wet ground. But it’s worth giving it a try, as long as you accept that some may die.
Tell me if this is a really stupid idea… what about lots of mulch, topped with a blanket of bubble wrap? I’ve planted dahlias for the first time this year; looking forward to seeing if they like this garden. I’ve got them in a big raised bed (60cms high, 1.5m square) with glads, lilies and aquilegias. We can get very harsh winters, down to -20C, with deep snow, but for the last two years the winters were long but not so challenging. Spring can also be a problem, with an early spring that gets the buds growing and the bees on the go, to be followed by a late snap of freeze & snow. Any thoughts?
I’m not absolutely sure – I don’t think dahlias would survive when it gets to minus 20, but if you’re happy to take a risk, it might be worth trying it. I’ve noticed from the comments I get here and on the YouTube channel that individual gardens vary quite alot and that it’s not just about the weather zone you live in, but whether your own garden is particularly sheltered or exposed within that zone. The bubble wrap might help, but it might not. Personally I find storing dahlias quite a fiddle, so on the odd occasion I have stored one, I’ve often lost it due to it getting too damp. Good luck.
Did you try with mulch and bubble wrap??
Not bubble wrap because it doesn’t decompose. But if you put a nice pile of organic matter on top to protect from frosts, it will slowly decompose and feed the soil too, so some dahlias come back bigger and better. Although if you have heavy clay soil and live in a wet area, then dahlias won’t like sitting in cold, wet soil. Give it a go, be prepared to lose one or two and see how it turns out.
Swan Island Dahlias (Largest grower in the US) zone 8 does suggest plastic (under/over mulch) over the top of your dahlias for the winter…BUT take it off and reuses it next winter. It keeps the tubers dry.
Interesting! I haven’t seen that used here in the UK, and I’ve interviewed some real dahlia experts, such as Steven Edney whose family have bred dahlias for generations and Sarah Raven who is partly responsible for the huge increase in popularity in dahlias in recent times. But it may come here at some point – sometimes it’s just a question of custom, although it may also have something to do with rainfall levels.
Do you have any thoughts on when its best to move dahlias? I did a mixture of lifting them and leaivng them in, but i need to move some of the ones i left in. Do i move them now and pot them up inthe meantime or leave them till they have got going and then move them. Decisions, decisions. Thanks in advance. Anna
I’m not entirely sure, but I think it would be fine to move them now and pot them up. I’ve never moved any once they got growing, but I’ve always instinctively felt that that would be more disruptive.
Thank you, I think I’ll try a few and keep my fingers crossed!
Transplant update! I dug them up and put them in big pots. The tubers were in good condition (they were from cuttings last year)and are now happily shooting away- within a week. I’m glad I did it straight away.Thanks for the advice. Happy Easter.
Great – glad it all went well.
Here in East Yorkshire, I grow dahlias on my allotment. I cut down the stems in Autumn. Then put a bucket or plastic bin over the it; weighted down with a brick or something similar. They have always survived the winter fine. The varieties I am very solicitous about, I place a home- made, polythene cold frame over. Bucket, bin or frame keeps off the wet and the frost.
That sounds like a great idea.
How much approx. height do you leave of dahlia before covering with compost? And when do you do this? Thanks
I cover the dahlias in October, once the first frost has killed most of the foliage and the plant is mainly a sorry heap of dead or blackened leaves. I remove absolutely all the stems as they are hollow and I have the idea that if rain got in and froze then it would kill the plant. Then, if I remember, I put a cane or marker in to show there’s a plant there. Not all such markers survive so occasionally I discover I’ve planted something else too close to it, as the foliage doesn’t emerge from the ground until early May-ish (depending on the weather).
Also in the South East – I have left mine in the ground for the last 4yrs or so, & they always tend to come back (I have lost a few) – I cover them with a mulch & then pin some membrane (or an old compost sack) over the top as an extra layer of protection from the cold but more importantly the wet – just make sure to remove it once the danger of frost has passed,. Granted not the most subtle in the garden, but mine are mostly at the allotment for picking so I don’t mind it looking a bit ‘make-shift’ up there !!
That’s a good idea, particularly this winter. It’s been raining continuously here for weeks.
I live on Yorkshire Lancashire border and it doesn’t work here mainly due to the wet I think not just the cold
I’m sure you’re right, especially if you have heavy soil.
I’ve learned something here. I’ve only ever grown the Bishop dahlias with their black foliage and they died on me every time I bought them so I totally gave up on dahlias in disgust. It sounds like I would do better with the ordinary ones so I am willing to try those next year – along with slug control. Nice to learn something I didn’t know.
Thank you! The London slugs and snails are particularly domineering, I seem to remember…