Don’t dig up dahlias for winter! What to do instead….

November 12th, 2017 Posted In: Gardening know how

I don’t dig up dahlias to store them at the end of the summer.

I’ve been growing dahlias for fifteen years, and I only dug a few up once. They died.

But the dahlias I’ve left in the ground, year after year, have filled our late-summer borders with glorious colour.

Don't dig up dahlias!

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?’

I don't dig up dahlias - all these are 3+ years old.

Our dahlia border

Of course, those who have ‘proper gardens’ almost always dig up their dahlias. Then they store them expertly, and they have places to do so.

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.’

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.

Keep snails off dahlias?

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.

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.

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.

Don't dig up dahlias - Henriette has survived three years without being dug up.

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.

If you don't dig up dahlias, they can spread.

The dahlias that do come back seem extra vigorous, perhaps because of their nutritious mulch meal. This is ‘Con Amore’.

So it’s a question of trial and error. And it also depends on where you live, – we’re in Southern England, so we have some quite mild winters and some harsh ones. It’s usually considered equivalent to a US hardiness zone 8, although it doesn’t quite match.

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 video, which also features the beautiful gardens at The Salutation (now closed). Or you can read his advice in this blogpost on growing dahlias.

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. She has even managed to keep the black-leaved ‘Bishops children’ alive!

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.

See ‘Don’t dig up dahlias’ on YouTube

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 because my favourite gardening saying is ‘Gardeners Learn by Trowel and Error’, I’ve put it on some mugs, a t-shirt and a tote bag.  It’s remind you not to worry about gardening – just give it a go and enjoy it! They’re available from the Middlesized Garden Spring Store.

Middlesized Garden mug

This mug is also available in blue – it’s to remind you to take a break and enjoy your garden! Available from the Middlesized Garden Spring Store.

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.

Don't dig up dahlias for winter...what to do instead

48 comments on "Don’t dig up dahlias for winter! What to do instead…."

  1. pete says:

    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 ?


    1. 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.

  2. Brian says:

    I ask the question, when do Dallas start to shoot out doors if left in the ground over winter

    1. Dahlias should come up around the beginning or middle of May, depending on what your climate is like.

  3. Marianne Hopewell says:

    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!

    1. 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.

      1. Marianne Hopewell says:

        Thank you! I’m going to give this a try.

  4. Jen says:

    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!!

    1. 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.

      1. Emma says:

        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

        1. 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.

        2. Alan says:

          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.

          1. 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.

        3. Clare says:

          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

  5. Rashpal Sumner says:

    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

    1. 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.

      1. Sarah says:

        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?

        1. 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.

  6. Rhys says:

    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).

    1. 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.

      1. Kim says:

        What growing zone do you live in?

        1. 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.

  7. Lucy says:

    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.

    1. 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.

    2. Emma says:

      Is this still true for you? I too am in the midlands and just toying with the idea of leaving mine in the ground..

      1. 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.

  8. Arabella says:

    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?

    1. 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.

    2. Louisa says:

      Did you try with mulch and bubble wrap??

      1. 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.

        1. ann says:

          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.

          1. 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.

  9. Anna Greenwood says:

    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

    1. 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.

      1. Anna Greenwood says:

        Thank you, I think I’ll try a few and keep my fingers crossed!

        1. Anna Greenwood says:

          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.

          1. Great – glad it all went well.

  10. Louis Colombi says:

    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.

    1. That sounds like a great idea.

  11. Judy Stannard says:

    How much approx. height do you leave of dahlia before covering with compost? And when do you do this? Thanks

    1. 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).

  12. sunrise gardens says:

    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 !!

    1. That’s a good idea, particularly this winter. It’s been raining continuously here for weeks.

  13. Angie says:

    I live on Yorkshire Lancashire border and it doesn’t work here mainly due to the wet I think not just the cold

    1. I’m sure you’re right, especially if you have heavy soil.

  14. 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.

    1. Thank you! The London slugs and snails are particularly domineering, I seem to remember…

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