Dahlias -Overwintering Dilemmas- 19 November 2019

I’m not usually a ditherer. I have a plan of action and I just get on with it. But the weather this autumn has put a spanner in the works. Unprecedented amounts of rain mean we are five weeks behind schedule with all jobs in the garden. And I am only now managing to sort out and store my precious dahlia collection.

This year, I’ve decided to leave half in the ground – in a raised bed with free-draining soil- and bring half indoors. This way, I’ve cut my losses. I’ll have some plants indoors to take cuttings from next spring, even if the ones outdoors fail to survive.

Here’s what I’ve done with the ‘outdoor’ dahlias:


1. I’ve waited until all the foliage has been blackened by frost. This sends the plant instructions to go into dormancy.

2. I’ve removed half of the foliage and dead flower heads. The remaining foliage has been folded over to cover the plant. Stems are hollow, so if you cut back stems and leave them upright they act like straws, directing rainwater down to the tuber.

3. I’ve put a 3″ deep mulch of compost over the tubers, followed by 6″ of dry leaves or straw.

4. Dahlias need to be kept dry and frost free, so I’ve covered the bed with some cloches, and packed the ends with dried leaves. These 1.3m by 3m beds are mounded up like ridge and furrow farm land. They are no-dig which also seems to aid drainage over winter by protecting the soil structure. No-dig basically means adding a few inches of compost every time you harvest a crop, and simply re-planting through the compost. No back-breaking digging is required.


For my indoor ‘insurance policy’ dahlias I’ve done the following:

1. Waited until the frost has blacked the foliage. Checked the soil. It is like suet pudding, wet and claggy. Heavy clay. This is an area of garden due a lot of compost mulch over the winter.

2. I’ve gently dug out the dahlias, being careful not to bruise them. Wounds are vulnerable to rotting, so care needs to be taken.

3. I’ve cut the stems back to 3″ and turned the tubers upside down to drain. They will go into a frost free potting shed.

4. When drained, I’ll store the tubers in dry vermiculite, straw, or compost, in the dark, under the potting shed table. Temperatures need to be 2-3C. Dahlias will survive a few degrees of frost- if they are dry. If it gets very cold, I’ll throw some fleece or old blankets over the tubers.

In February, I’ll place the tubers in seed trays of compost in gentle heat to bring them back to life. When they have shoots 1″ tall, I will split the large tubers in half with a sharp knife, making sure both halves have some stem.

I’ll also take basal softwood cuttings when shoots are 1″ tall, using a sharp knife and taking a small sliver of tuber with the cutting. These will be grown on in a frost free greenhouse and planted out end of May. Cuttings will make good size tubers and will flower in one season.

You can lift and save tubers from seed-grown dahlias as well. Just save the best ones, as seed produces very variable results.

Which option are you taking with your dahlias?


It’s fascinating to hear that dahlias have been grown in Europe for 200 years. They originally came from Mexico and were grown in the botanic gardens in Madrid towards the end of the 18th century.

Dahlias are named after Andreas Dahl, a Swedish botanist, scientist and environmentalist. Plants come in every colour -apart from blue! The smallest are the Lilliput Series and the largest are dinner plate sized, a foot in diameter.

Dahlias are categorised by their appearance; there are waterlily, Pompom, collarette and cactus types. Something for everyone, really.

Here’s some of my favourites from my cut flower garden.

Arabian Night. Deep, dark velvety red. A stunning dahlia for cut flower work.

Nuit de’Ete, a lovely deep red cactus type. Lasts two weeks in a vase.

Nuit de’Ete amongst cosmos, persicaria and Ammi.

An pretty un-named variety grown from a packet of seed. Single flowers are much loved by bees and butterflies.

Dahlia David Howard. The best orange variety. Strong growing with long lasting flowers. Very beautiful in low autumn sunshine.

A very good book on dahlias has been written by Naomi Slade. Highly recommended. Just beautiful to sit and peruse over the cold winter months to come. When we will all need something cheerful to look at.

There’s a review of the book here : https://bramblegarden.com/2018/06/24/dahlias-beautiful-varieties-for-home-and-garden/

My dahlia tubers come from Gee Tee Bulbs: https://www.gee-tee.co.uk/bulbs/dahlias

Links: National Dahlia Society: https://www.dahlia-nds.co.uk/

In a Vase on Monday ( although this is Tuesday- I still like to join in when I can ) https://ramblinginthegarden.wordpress.com/category/gardens/in-a-vase-on-monday/

Follow me on twitter @kgimson

On instagram at karengimson1

Thank you for reading. Please leave a comment below and let me know what you are growing in your garden at the moment.

And, a photo I haven’t shared before. A picture of my mother in law Joan. Regular readers will know that I grow my cut flowers to keep a connection with Joan. It’s something we both love and it’s a way of sharing my garden with her now she is living in a care home.

22 thoughts on “Dahlias -Overwintering Dilemmas- 19 November 2019

  1. I don’t put so much fuss into dahlias. They can stay in the garden all year. I only dig them to divide or renovate them. If they stay in the same place for too long, they get rather tired looking as the tubers get crowded too close to the surface of the soil. I should grow more, but have refrained because they can get so prolific. I will not likely every add to what is here. There is (only) one here that is a remnant of a large group that was dug and disposed of years ago. Even though I am none too keen on the grapefruit like color, I intend to keep it going. The others are rather simple colors; plain red, plain yellow plain orange, etc. For now, they are in contained colonies.

    Liked by 1 person

  2. Karen half out and half in, wise decision with the Dahlias. With the Dahlias Outdoors you have done a real gardening work even with glass bells, I love it. I have learned a lot, thanks. Raise Dahlias to Store Inside. It is a long process that takes place in February by planting the tubers in compost seed trays and having 1 “shoots divide the large tubers in half. Then you can take basal cuttings of softwood and make more dahlias. It is a fantastic world the one of the Dahlias that you have explained so well: I love it. The History of the Dahlias has enchanted me: to think that the first ones that were cultivated outside of Mexico were in Madrid. Your photos are magnificent like all your dahlias that I love: They have made you smile.Your dear mother-in-law Joan is beautiful in the photo.It is very beautiful.The flowers always keep you together and that Joan always likes you.Much love, much health, many strengths and lots of encouragement for all your family and for you and Mr B. Take care and don’t get wet with the rain Keep warm and layers of warm clothes Very affectionate caresses for Grace and Meg Very affectionate greetings from Margarita xxx

    Liked by 1 person

  3. It is interesting to learn about how to care for plants – even when I don’t grow them myself…. yet! Perhaps I will, one day, when my long-planned vegetable garden with raised beds and a little fence materialises! (Next year, or the year after…?!)

    Liked by 1 person

  4. I am lucky as we do not have long periods of sub-zero weather, so my dahlias just get left to perform as perennials. However, this year we have had exceptionally heavy rain and the autumn garden is soaked and wet as I have never seen it. Some of the leeks are rotting in the ground. Things might be different this year. Amelia

    Liked by 1 person

    • Thank you Amelia. The wet makes them more susceptible to the cold weather. Dry cold is ok. But wet cold is fatal. Here, the farmers are struggling to get maize crops off the fields. And there’s a farmer in Lincolnshire who has lost a £1 million crop of potatoes because of the wet. Plus they can’t sow autumn barley etc, so the fields are standing empty. Karen

      Liked by 1 person

  5. I have previously managed to overwinter dahlias in the ground in the east of Scotland where it is pretty dry but cold and well below zero for long spells (in fact it was -5 this morning!) but it is a gamble. In my experience they can take a bit of cold, especially with a heavy mulch but prolonged wet is sure to turn them to mush. Over the years my stock has gone up and down a fair bit with the vagaries of our climate.

    Liked by 1 person

    • Thank you Keith. Yes, my stock has gone up and down according to the weather. Even digging them up isn’t fail safe. Yet they are cheap enough to buy, luckily. And very easy to grow from seed. Good luck with your dahlias. Thanks for reading.


Please leave a comment and let me know what you think. It's nice to know I'm not talking to myself on here.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s