How to Lift, Store, and Divide Dahlia Tubers for Stronger, Earlier Blooms Next Year

What dahlias do from spring to late fall is a miracle of Nature! But it’s how you treat the tubers over winter that makes it possible… These strong and vigorous perennials will spring from their underground storing organ and soon grow tall, with lush foliage, and by midsummer, you will also enjoy their brightly colored, big, sometimes massive blooms in warm shades of red, orange, yellow, purple or white, and they will decorate your flower beds and borders till the end of season!

In fact, if dahlias are now a household name in gardens all over the world, they originate from Mexico and Central America, where winters are very mild indeed! And unless you live in a very hot climate, the tubers won’t survive over the cold months…

That’s why you need to overwinter your dahlias and it’s also the perfect time to multiply them by dividing the tuber clumps. Storing dahlias in winter is not the same as storing other bulbs and tubers since they need a little extra care. This guide will walk you through exactly how to dig them up, store them the right way, and divide them so they’ll be ready to give you another incredible show next season.

Can You Leave Dahlias in the Ground Over Winter?

Here in California, we’re lucky. Winters are mild enough that dahlia tubers can usually stay in the ground year-round. With a little mulch for protection, they rest quietly through the cooler months and wake back up once spring arrives.

But that’s not the case everywhere. Dahlia tubers are tender and can’t handle frost. Since they’re fibrous and filled with water, freezing temperatures cause their cells to burst, leading to rot and tuber loss. The freeze-thaw cycle or too much winter moisture makes things even worse. That’s why lifting and storing tubers is the most reliable way to protect them in colder climates. In places like Zone 5, where the ground can freeze several feet deep, dahlias simply won’t survive outdoors. Gardeners there need to dig them up in fall, store them safely indoors, and replant them when spring returns.

Even in slightly warmer regions, such as Zone 6b, dahlias may still need protection. At Love ’N Fresh Flowers, for example, they’ve had success overwintering them in the ground by covering the beds with thick layers of leaves, straw, and tarps. This heavy mulch insulates the soil well enough to keep the tubers alive until spring.

So the real answer depends on your zone. In frost-free areas like much of California, dahlias can stay put. In colder zones, lifting, storing, and dividing is the safest approach. And of course, some gardeners prefer the simple route—skipping the work of storage and buying fresh tubers every spring.

How And When To Lift Dahlia Tubers Out Of The Soil

The first phase of the overwintering process is to take the tubers out of the soil in a safe way… And we can start with the timing.

1: Lift Dahlia Tubers in Late Fall and Early Winter

The timing for uprooting your dahlia tubers out of the ground depends on the weather and climates where you live: it is usually between late fall and early winter, but it will be the plant itself to give you the “go ahead” signal.

• Wait till the whole plant has gone brown. This is the key indicator, and don’t worry, it won’t be dead; it simply feeds all the energy back into the tubers.
• This will usually happen after the first frost, even 5 to 7 days later, and, unless there’s a risk of strong and persisting freezing, you do have a bit of time…
• Dig your dahlia tubers up before frost becomes intense and persistent. Dahlias will tolerate some frost, especially because the soil itself protects the tubers, but for short times (like overnight) and not too severe.

Now, wait to uproot the tubers, there are a few steps you need to take beforehand…

2: Cut Back Plants and Label Before Digging

Before you actually lift the tubers of your dahlias out of the ground, there you will need to do a few things, and here they are.

• Cut the dahlias, but remember to leave a few inches of the stalk out of the soil. You will need them, but cut to the main stem, about 2 to 5 inches above the ground (5.0 to 10 cm). You can use secateurs of bypass loppers for this.
• Place the labels next to each dahlia plant; all tubers look the same, and if you want to know which dahlia you are planting where next year, you will need the labels.

And now it is time to take your dahlia tubers out of the soil – here’s how…

3: Use a Garden Fork to Lift Tubers Gently

Lifting dahlia tubers out of the ground is a fairly delicate operation, so, be gentle and careful…

• With a fork, lift the soil, dig down deep at about 1 foot from the plant (30 cm) then, gently raise the whole clump around the tuber.
• Do not use spades or shovels; they can literally cut the tubers.
• Pick the dahlia from the stem you left over the ground and remove the tubers from the soil gently.
• Remove any dead or rotting tubers and roots. Anything that is soft, rotting, or tubers that are wrinkly and shriveled will go on your compost heap.

Now, there are a few points to make here:

• If you pierce a tuber with your fork, it is actually no problem. You can leave it, the wound will most likely heal over the winter months.
• If a tuber with no eye gets detached and falls off, then throw it on your compost heap because it will not germinate. We will see how to recognize dahlia eyes later on in this article.
• Keep the labels with your tubers!

And now – no, it is not yet time to store them…

4: Clean, Trim, and Dry Tubers Before Storage

There are a few steps to take before you actually put your dahlia tubers away for the cold season…

• Clean the tubers from soil. You can easily do it by hand or even with a hose, but don’t leave soil on them, it may have bacteria and it will stop you from seeing how dry the tubers are.
• Cut the stems; now you don’t need them anymore, so, get your loppers and cut them down close to the base, to the point where they are no longer hollow.
• Dry the tubers; just place them somewhere warm and well ventilated for a day or more. They need to become dry but not shriveled! This is very important and it is something we don’t look at with many bulbs, but dahlia tuber should never wrinkle, or they mag die…

So, once you see that your dahlia tubers are dry but still full and plump, it is finally time to put them in a safe place for the winter months!

5: Store Tubers in a Cool, Dark Place for Winter

Of course, gardeners have many methods for storing dahlia tubers over the winter months, butwe checked with a professional grower to find out the best way…

• Use cardboard boxes as containers; they seem to be the best, because they keep the humidity right.
• In fact, here is an important difference between dahlias and other bulbous or tuberous perennials; tubers need to stay lightly humid all over the winter months, otherwise they will dry up and shrivel, so…
• Gently mist some water on your dahlia tubers.
• Now you can store them, and you can simply use a grocery bag, place the tubers inside with the label, and put them in your cardboard box in layers. Alternatively, you can use paper (even newspapers) to cover each layer, and even place the tubers in wrapping foil, as suggested by the American dahlia Society, then of course, cover them with paper. They need to stay in the dark! My favorite way is with grocery bags, if you want a tip…

At this stage, you can choose to give your dahlia tubers a helping hand with retaining a but of moisture, but without getting wet. It is up to you but, if you want, you can…

• Place the dahlia tubers in a humidity retentive medium. For example, a mixture of 1 part bark chips, 1 part peat moss (or substitute) and 1 part sand. Alternatively, sand and vermiculite will do just fine.
• You can either use this medium to cover the tubers, or simply fill the grocery bags with it. Whichever you feel more practical to you. One thing though, don’t get the different clumps of tubers to touch each other.
• Place the boxes with the dahlia tubers in a cool and dark but well ventilated place. The temperature should be between 40 and 50^oF (which is between 5 and 10^oC). The odd peak or low out of this range is fine, but never for a prolonged period.

Now you may think it is all done and you can forget your dahlia tubers till spring? Not exactly…

An Alternative Method: Winterize Dahlia Tubers In Pots

Here is an alternative method for winterizing dahlia tubers that is gaining popularity, because it is very simple, and it is very much used for dahlias you grow in pots.

• Simply cut the dahlia stems to just above ground level.
• Turn the pots to the side, so that the stems are horizontal.
• Allow the soil in the pots to dry up.
• Place the pots in a container and cover it with some fleece and paper, to keep the tubers dark over winter.

The rest is exactly the same; find a cool, dark, well ventilated place and store them away till spring.

However, this method, while it is very simple, does not allow you to check on the tubers, and the soil may not be as healthy as you think. There could be bacteria that have accumulated over the months, and they may cause problems to your dahlia tubers, while you cannot see them.

What is more, you would still need to take them out of the pots to propagate them and you need to do it regularly if you grow them in containers, or they will quickly outgrow them. And

How To Care For Dahlia Tubers Over Winter

With most bulbs and tubers, we store them away over winter and look at them again when spring comes, but dahlias are a bit different… They need to stay lightly humid, so…

• Do check your dahlia tubers regularly; if they are starting to shrivel, give them a light misting, then place them back.
• Make sure you cover them again after checking, they need to stay in the dark, or they risk germinating early.

For this reason, grocery bags are the perfect solution, while wrapping paper will preserve the humidity, it may also encourage bacteria to spread if the conditions are not perfect. And they are great to keep the different varieties separate.

So, every two weeks or so, go and visit your tubers, and make sure they keep firm and plump for when they have to sprout and give you new and healthy blooms. But there’s a final point to make…

How To Propagate Dahlias From Tubers

Overwintering dahlias is also a good change to propagate them, and we usually divide the tuber clumps every two years. But first you need to recognize the eyes.

Identify the Tiny Growth Eyes That Produce New Dahlia Plants

Dahlia tuber eyes are the gems that are starting to form, and each will become a new plant. They look like little bumps under the base of the stem. Note that they are not on the tubers themselves. By spring, some of them will look like little sprouts, ready to grow. They look a bit like those on potatoes.

Here is your choice and I cannot give you one solution, because…

• If you are good at recognizing eyes, you can divide the tuber clumps when you uproot them.
• If you are not confident with the appearance of the eyes, you can divide the tuber clumps before you plant them, in spring. But in this case, the roots will be a bit harder to cut. Not a major problem though.

Dividing Dahlia Tuber Clumps to Ensure Each Section Has a Growth Eye

Dahlia tubers are attached to the base of the stem, and the eyes grow just there. You cannot cut a tuber in two as you do with potatoes! So…

• Divide the whole clump of tubers at the base of the stem.
• Make sure that each new clump has at least one eye.
• You may have to cut the stem in two (or more) vertically, to divide the eyes.

Yet again, if in this process an eyeless tuber gets detached and falls off, recycle it in your compost heap because it is not going to germinate.

Overwintering Dahlias For Great Blooms Year After Year

And this is all! Yes, dahlia tubers do need a special treatment, compared with other tuberous and bulbous species, but if you follow these instructions, you can be sure that you will have lots of showy, colorful and healthy blossoms year after year – actually, you can even get more when you split the tiber clumps and propagate them!