The Ultimate Guide to Lifting and Storing Dahlia Tubers
To lift or not to lift? That is the question!
Can you believe that some gardeners treat dahlias as annuals and throw them away at the end of the season?
It just seems such a waste.
If you live in milder parts of the country, you can probably get away with leaving your tubers in the ground over winter, provided you place a good layer of mulch over them at least a few inches deep; this maybe enough to protect them from moderate frosts.
For the rest of us, I feel that overwintering is the best option, and it’s not that difficult.
Follow my 8 easy steps to guarantee your dahlias survive the winter and grow back healthy and strong next year.
Step 1: You Will Need…
I lift my dahlias each year and store them for the winter. Here’s a list of everything you’ll need:
- A garden fork to lift them out of the ground without damaging them.
- A brush for cleaning.
- Newspaper and cardboard boxes.
- Tags or labels so you can identify them next year.
- Compost or fine wood shavings or vermiculite.
- Secateurs and/or a sharp knife should you wish to divide them.
- A cool frost-free place to store them, such as a garage.
- If you live in the far north, you may need extra insulation, and I used hessian before, it’s well-insulated and worked well.
Step 2: Timing
You’ve probably heard that dahlia tubers are sensitive to frosts and should be lifted before or immediately after the first frost.
While the tubers should never be subjected to frost, I feel that lifting them too early or even immediately after the first bout of frost is a bad idea.
You see, the tubers need to swell up and mature before they’re lifted, and this usually happens after the first frost.
I’ve pulled them up early before, they were green and I found it difficult to locate the eye, which made dividing them nearly impossible.
I’ve never seen dahlia tubers die off after the first frost as they are under the soil and well insulated. I suggest leaving them in place for a week or two so they can swell up, I’ve had good results by doing this and have never experienced any problems.
This is a crucial step as the tubers put on essential growth and maturity at this stage; it’s their final oomph before entering dormancy.
Obviously, if the weather forecast predicts harsh frosts, you’ll want to lift them, but they can easily survive a week or two into light, late autumn frosts.
If you’re worried about aesthetics, you can trim the dahlia stems, leaving a 6-inch stem at the base, or leave them as they are.
Step 3: Dig ’em Up
After the dahlias have been left in the ground long enough to “cure”, it’s time to lift them.
I’ve lifted hundreds of dahlias over the years, and I’ve found the best way to loosen the tubers is to:
- Trim the stem six inches above ground level – I do this so I have something to hold and pull the tubers with.
- I then use a fork and gently fluff up the soil around them.
- I then gently ease the tubers out, using the fork as leverage.
I’ve tried lifting them with a spade before but I damaged the tubers by slicing them so I prefer a fork or hand tool.
Step 4: To Wash or Not To Wash?
I usually wash my dahlia tubers to remove any soil, but plenty of gardeners I’ve met say this dampens them, and wet tubers are more likely to rot when in storage.
I think they’ll be just fine provided they’re dried sufficiently after washing, but either way, it’ll be easier to clean them with a brush than just your fingers.
Here’s how I do it:
- First, I snip off the excess tails; that’s the wispy ends of the roots.
- Next, I snip off the stem if it’s overly long; I usually leave at least 3 inches.
- I then hold the tuber bunch upside down and under running water.
- Using a 1-inch painters brush, I ease off any mud.
The next step is perhaps the most important:
- I turn the bunch upside down and let it dry for at least a week, preferably in a garage or porch or somewhere sheltered.
If you want to divide your dahlias, I recommend washing them as this removes harmful organisms. If you don’t, then cleaning is entirely optional.
Step 5: Should Dahlias be Divided After Lifting or in the Spring?
Dahlias tubers can be divided to create more plants, but each tuber must have an “eye”; if it doesn’t, then it won’t grow next year.
The eyes are often tricky to locate, especially if the tuber has only recently been lifted and/or is unwashed.
By contrast, I’ve found that it’s far easier to locate the eye and divide the tuber in the spring.
The only reason I can think of why a garden would divide them after lifting them is to save space. Tuber bunches can grow big, and if your storage space is limited, it might make sense to split them straight after you’ve lifted them.
I have always left my tubers in storage until spring and then divided them then, so far I’ve had very good results and each year, I get plenty of new tubers to plant out.
Step 6: Preparing Your Box
I use cardboard boxes lined with newspaper, but I’ve seen gardeners use plastic pots, tubs and even hessian to store them,
Here’s my recommended method:
- Trim the stem to within an inch of the cluster, being careful not to damage any eyes.
- Cut a small 1-inch hole in each side of the box, near the top, for ventilation.
- Line the base and sides of the box with old newspaper.
- Place a 2-inch layer of dryish compost at the bottom of the box and lay the tuber bunches onto it, ensuring they don’t touch each other.
- Infill with more compost until there’s space for extra tubers, and infill more until all the tubers are covered.
- You can leave the stems exposed above the surface or cover them; it doesn’t matter, provided the tubers don’t touch each other.
The compost should be fairly dry but not so dry that it absorbs moisture from the tuber but certainly not wet that it rots it.
I usually buy a couple of bags of compost from my local garden centre and open them on my garage floor and aerate it for a week before I use them to store my dahlias.
Alternative to compost: Compost doesn’t wick the moisture away from the tubers so some gardeners use vermiculite or wood shavings but to save on costs and to simplify the process, I just use semi-dry compost, preferably a light, fluffy type.
Step 7: The Best Place to Store Dahlias Overwinter
And this is the big question I see being asked all the time; exactly where is the best place to store dahlia tubers over winter?
As a general rule of thumb, I’ve found that the tubers should be kept between 5° and 10°.
Below 5° and you’re skirting close to frosty conditions, and above 10°, the tubers may start to sprout.
In the UK, most gardeners will be able to keep them in sheds or garages. However, those living in the north may need to locate them in a warmer spot or cover them with breathable but insulating material, such as hessian or similar.
As for me, I have a porch cupboard that is relatively sheltered, and I place the boxes on top of each other and against the outer house wall for a bit of warmth.
I recommend lifting the boxes off the floor by an inch or two at least.
The ideal humidity for dahlia tubers is well above 70° but this isn’t always possible in a garage or shed so I just make do with what I have.
Step 8: Keeping an Eye on the Tubers
Some of the tubers may rot, and these must be removed from the box before disease sets in and affects the other tubers.
I check the boxes once a month and fish out any squishy tubers; I don’t worry about any tubers looking shrivelled as that’s normal, as long as they are still reasonably firm.
If the tubers look really shrivelled, I may spray a little water into the compost to moisten it, but not enough to cause the tubers to rot.
Dahlias can be grown as annuals, they can be left in the ground over winter with a layer of mulch on top, or they can be lifted and stored until spring.
I’ve had lots of success with the method described above, but others do things slightly differently, so don’t be afraid to try a different approach!
All of the dahlia photos on this page were taken by me in 2021 and all were grown from tubers I’ve previously divided from older plants over the years.
Meet The Author: Hannah Miller
Hannah is a former NHS administrator, mother of two and keen gardener with a horticulture qualification who loves growing new plants and experimenting in the garden.
She enjoys gardening as much as she cares about the environment and likes to share her knowledge with others.
This year is all about pollinators, and Hannah has set herself the goal of only buying new plants that attract pollinators; she aims to make the garden as bee and butterfly friendly as possible.
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Hannah Miller has been growing dahlias for many years, and the photos on this page were taken by her.
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