How to Store Dahlias Over Winter

Dahlias are easily my favourite flower of all time but they have had their ups and downs over the years. Back in the 1800's they were known as Georginas and they were very expensive. They were a real status symbol costing one hundred pounds a tuber. Wealthy families would plant large borders full of them and invite guests round for afternoon tea to show them off. By the 1950's they had come down in price and in the drab era of brown and beige lost their attraction. They were considered showy and vulgar and many of them were lost.

Nowadays there are so many varieties available to choose from that they do not need to be dramatic in a vulgar way. There are so many pretty varieties and new forms being developed by breeders and they continue to go from strength to strength.

Unfortunately though they are not hardy and will turn their nose up at any sign of frost.

Dahlias are at their best in the early late summer & early autumn, in the UK this is August/ September time. They originate from equatorial regions such as Mexico, Columbia and Central America, where the days and nights are equal lengths. So the autumn equinox which falls in late September is the day on which they should be at their peak here in the UK. In reality many regions in the UK will have already had a mild frost in some years.

For our plot in Hampshire, in 2018 this was Sep 25th and in 2019 it was Sep 7th !!!!! eeeek!!!! but in 2020 and again in 2023  we had a bumper years  and it was so late at the end of October/ November that I can't even remember the date. 

When to lift Dahlias

It's is best to leave Dahlias in the ground for as long as possible to grow nice big tubers, this way they have a better chance of making it through the winter. Once the frost arrives  you will know it is time to lift as the leaves will turn black and wilt.  

In areas which do not suffer too much from a hard frost lifting is not necessary but for those in colder regions it may be wise to lift and store them to secure your tubers for the following year, or if you have wet clay soil/poor drainage which will rot the tubers through winter.

In some southern parts you can experiment with leaving a few in the ground to see if they do make it through the winter just ensure they have a good covering of mulch and free draining soil. 

​Labelling Dahlias

Ensure that all plants are clearly labelled before you begin lifting. It's too easy to get them mixed up - the tubers really do all look the same. During the summer when they are blooming I label each one meticulously ensuring the correct variety using a permanent marker pen into a plastic wrap label around the stem.

Lifting Dahlias

Begin by cutting down all of the stems & leaves, leaving just 10cm or so of a main stem to help lifting.

Using a garden fork loosen the soil around each dahlia and lift the whole tuber out of the ground. Try to do this on a dry ish day so that the excess soil can be easily brushed off. Take as much soil off as possible without damaging the tubers, so bashing them on the ground is a no no!! broken tubers will allow disease to enter the tuber.

Drying / Short Term Storage

Once all of your Dahlias are lifted store them in a cool dark place which is frost free until you are ready to wash and split them. You are essentially removing them from the ground to ensure that the frost does not damage them and putting them somewhere safe out the way to dry out a little bit. I store mine in plastic crates in my garage for a few weeks until I have the time to deal with them.

Washing Dahlias

If you are intending on splitting tubers then you will need to give them a good wash to remove the soil, this just makes it easier for splitting and a much cleaner job. It also removes any pests which would over winter and potentially eat the tubers.  

It's a dirty job and the power from your regular kitchen tap will not be strong enough to clean the tubers well so a hozepipe with a string jet nozzle is best. Once they are washed they will need to be left for a few days ( Frost free) to dry out a little before storage . 

Dahlia Anatomy & Splitting

Each plant consists of a stumpy stem or stems and will have several swollen parts attached. They are really not the prettiest things to look at ! These are called tubers and to grow into a successful plant each Dahlia needs a tuber with at least one eye. The section where all of the tubers and stems meet is called the crown.

Dahlia stems will grow from buds/eyes on this crown. Look very closely all around the crown of the tubers for the eyes and you will be able to see small freckle like spots. Some tubers will have lots and others just a few.  They can be difficult  to spot so sometimes it may be best to store them whole until spring when they are easier to see just as they begin sprouting. Remember the tubers are not roots – they are a food store for the plant and if a tuber does not have an eye then it will not grow no matter how much care and attention you give it.

It can be difficult to know where to start splitting but if you begin by splitting a tuber in half across the old main stem you are half way there already. Try splitting between the tubers so that you get less wastage, but inevitably you will end up with a few which have been sliced through. Make sure that you throw these - they will just rot in storage and put the rest of your stock at risk. You can then split both of these halves again so you end up with four quarters if your tuber is really big.

Now it’s easier to look at each tuber and decide if it’s viable or not. Carefully check the crown of each tuber looking for at least one eye. Some will have none – these can be discarded but others may have many. Then simply cut this tuber away from the rest taking care to cut it away with the eye and some crown. Repeat this for each tuber in turn. If you are unsure if you can see eyes or not then there is no harm in keeping them all and checking them in spring when the eyes are much easier to see.

If you have any tubers which are a bit wobbly and broken remove these and do not store them - they will rot. At the same time you can also trim off all of the fine roots as these will not be needed for winter and new ones will be produced next season. Once you have discarded all the parts without an eye and done your trimming you will be left with a bunch of nice neat looking tubers. From that one clump which you planted in springtime you can get as many as 10+ viable tubers which will in turn make a huge clump of tubers for you to divide next year!

Winter Storage for Dahlias

There are a few different ways to store tubers but the below method is the one I have used for years and it works well for me with minimal loss. You may need to experiment with a few other ways to get a method which works for you. 

You will need a container to store them in such as a plastic box/bin, and a medium to cover them. There are so many mediums to store tubers but the most important thing is to keep them hydrated and frost free. You can use vermiculite, peat moss, spent compost, wood shavings etc. I now use wood shavings - the kind you can buy from the pet shop for rabbits. Simply take your container and put a layer of your medium in the bottom - just a couple of cm is enough. Place each tuber onto the medium and ensure that they are not touching then cover the tubers with another layer of your medium. You can keep layering the tubers until you reach the top of the box. The label which you used for short term storage can then be placed inside the container.

Once you have finished, pop the lid on and store them away in a frost free place at 5-10 ℃. It’s a good idea to check on them once a month until spring time, and remove the lids to allow excess moisture to escape. I find that the wood shavings wick the moisture away from the bulbs but keep the box humid enough to keep the tubers from shrivelling.  They should not be left to dry out too much or be left wet or they will rot. I check mine after 2 weeks first- yes every single one unpacked from storage checked and then packed back again - this is to remove any rotting ones as otherwise the rotting may spread throughout the crate all winter long. I then check them monthly/bi monthly after this and remove any rotting tubers. After the first check it is rare to find many rooting ones but its best to be safe. 

I have experimented using shrink wrapping film instead of storing in a medium but it rotted all of the tubers by sealing in the dampness. They really do need to be bone dry when storing like this and I haven't managed to get it right as yet so I will continue with the wood shavings for now and experiment with the cling film.

Labelling Dahlias

During one of my checks - usually in Jan/Feb is when I then label each one with a marker pen! This is when they are dry enough, before that the the market pen just won't stick.

If you only have a few tubers and are growing in the garden at home you won't mind too much about correct labelling but if you want to grow and propagate them by colour then correct labelling is a must. It's actually like an obsession and I don't think I have had a single year yet without at least a handful labelled as "unknown variety".  So now my Dahlias get triple labelled and writing on the tubers is a must for me now.  I've dropped crates of bulbs and gotten them mixed up, i've had the birds pull labels out of the ground and I've heard of mice gnawing through the string when tied to tubers! 

Firstly I label each tuber with a marker pen when they are in storage over winter ( Jan or Feb time) I don't do this straight after lifting because they are too wet and the marker pen gets clogged up. I then label each pot when pre sprouting with a label which follows the tuber into the field and then when the flowers can clearly been seen I double check all the labels in the soil and add another label tied around the main stem of the plant. Then I'm absolutely exhausted !!!

Leaving Tubers in the ground

You may not want to lift your tubers if you live in a particularly mild region. So in that case you can mulch over the top of them and leave them in the garden. or you may want to lift them but not wash and split them. They can be stored whole,  upside down to prevent the stem from rotting,  in bulb crates/ boxes with straw or scrunched up newspaper.

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