For many years, I thought it was too much effort to grow and save dahlia tubers. There are so many chores to complete as fall sets in. Digging up dahlias each year didn’t sound like a good use of my time. And figuring out how to dig and store dahlias was intimidating.

But that was before I became addicted to dahlias. Little did I know how rewarding it would be to grow these amazing flowers. And saving the tubers has become an important part of putting the garden to bed each fall.

As the weather grows colder, it’s time to make a plan for your dahlias. Dahlias tubers cannot survive prolonged freezing temperatures. So if you want to save them for next year, you must protect them. Let’s look at how to prepare your dahlias for winter.

Options for Winterizing Your Dahlias

How you overwinter your dahlias will depend on where you live and your winter temperatures. Once you have a hard freeze, the plants will die. In order to continue to grow those dahlias next year, you must protect the tubers from freezing.

Zone 10 or Higher

If you live in Zone 10 or higher, you can grow dahlias year-round. Lucky you! Dahlias are a perennial that will continue to grow as long as you don’t have below freezing temperatures.

Zone 8 and 9

Since dahlias are tender perennials, you can keep them in the ground all year long if you garden in zones 8 or 9. However, the plants will not survive any freezing temperatures. To protect your tubers from freezing, add a protective layer of mulch over your dahlia beds as a precaution. A 6-inch layer of straw, leaves, or pine needles will give your tubers the extra warmth they need when temperatures dip below freezing. The above-ground plants might not survive, but your tubers will be ready and waiting for next year.

Zone 7

While dahlia tubers can survive in zone 7 if buried deep enough, you run the risk that an extreme cold spell can cause you to lose your tubers. I garden in zone 7A and although I always dig up my tubers; I have sometimes missed tubers that survived and grew the next year. However, I don’t want to take a chance on losing all my stock, so I dig my tubers up.

Consider where you’re growing dahlias in your garden. We often have microclimate areas that are affected differently. If you’re growing dahlias in a protected area, then the tubers might survive. However, if growing in a non-protected area, chances are good that your tubers will freeze. Even in a protected area, a prolonged deep freeze could damage your tubers.

If you decide to leave your tubers in the ground, you’ll want to add a thick layer of mulch to the beds. Adding a 12-inch layer of straw or leaves can help to minimize loss. Top your layered bed with a thick tarp to further insulate your tubers from winter weather.

Zones 6 or Lower

As your garden zone drops, you will definitely need to dig up your tubers if you want to preserve them for next year.

Container Dahlias

If you’re growing dahlias in pots, you’ll need to protect them from the cold. No matter what zone you live in, if you have below freezing temperatures, the tubers will be more susceptible to freezing. You can bring your containers inside if you want to save your plants from the cold weather.

If you don’t want to save the plants but want to save the tubers, bring the container into a protected garage or shed. Store them in an area that will not freeze. When the plants die back, remove the stalks. This will protect your tubers for the winter and then next spring after the last frost, just pull the pots back outside.

The third option for your container dahlias is to dig up the tubers in your pots just as you do for those in the ground.

3 Reasons to Dig Up Your Dahlia Tubers

Obviously, if you live in a cold climate, you’ll want to dig up your tubers to protect them. But there are a few other reasons why digging up your tubers can be useful.

#1… Digging your tubers can expand your supply

That single tuber you planted last year has grown to become 4-6 tubers or more. If you want to increase your dahlia stock, then separating the tubers can give you more plants next year. The abundance of tubers also gives you tubers to share with others. Your friends and family would love to get dahlia tubers or plants for their garden.

If you’re new to growing dahlias, you might have grown them from seeds. Those dahlia plants have grown tubers you can save and replant next year. You can continue to add more plants from tubers and seeds each year.

#2… Digging your tubers gives you the opportunity to change tuber placement

Each year I like to add in some new varieties of dahlias. By digging the tubers up in the fall, it gives me the opportunity to rearrange the layout of my dahlias. Sometimes short dahlias get planted behind taller varieties and need to be moved to the front. Or you want to change out the color combination in a garden bed. By digging up the tubers, next year, you can place tubers so that every flower can be a star in your garden.

Tip: Keep a written record of your dahlia placement each year along with notes for planting next spring.

#3… Removing your tubers can help you amend garden beds for next year

While you can top dress your beds if you leave the tubers in place, when you remove the tubers, you have the option of adding more amendments deep into the soil. Digging up your dahlia tubers gives you the opportunity to improve your soil quality.

Steps to Digging up Your Dahlia Tubers

Step 1: Before a Freeze

There are several things to do BEFORE you have a hard freeze. First, you’ll want to label all your plants so you know what the tubers are. Place a tag on a bottom stem of each plant while you can still tell what the flower is. If you don’t have time to do this before a frost, or you can’t reach all the stems, you could also take a few pictures as a reminder of what grew where. Then label the stems once the plants die back.

I always place markers in the ground when I plant tubers in the spring so I can identify each plant. However, over the growing season, markers can sometimes disappear. As a backup, I make a chart of my tuber placement so I can refer back if the tag is lost. Before you dig, be sure you have labeled each flower clump. Otherwise, the tubers might be a surprise next spring.

The second thing you want to do before a freeze, especially if you know one is coming, is to get out there and cut every single flower and bring it inside. If you don’t have time, invite a friend or two over and let them cut bouquets for themselves. No need for your lovely flowers to go to waste.

Now it’s time to prepare your dahlias for winter. Follow the remaining steps to preserve your dahlia tubers for next year.

Step 2: Remove the Dead Stems and Wait

After a hard frost or two, cut off the dead plant stems. How do you know if it’s time? The plants will be completely dead and brown. When cutting your stems off, don’t cut to ground level. Instead, leave about 6-inches of the stems in place for each of your plants. Also, make sure that your plant tags are attached at the bottom of the stems so you can identify each clump.

After your dahlia plants have frozen, it’s important to allow them some time to go into dormancy. It’s best to wait 7 to 14 days after your hard freeze before you dig the tubers. This will toughen the tubers so they’ll store better during the winter months. This waiting time also allows next year’s eyes to become more visible. That’s helpful when you separate your tubers.

Step 3: Dig Up Your Dahlia Tubers

Now carefully dig up the dahlia tubers. A pitchfork or shovel can work to dig up your tubers. Dig around each plant clump about 10-12 inches away from the stems. Try to dig deep to get underneath the tubers. Once you’ve dug deep enough, gently lift the tuber clump by getting underneath the tubers with your pitchfork and lifting. You can use the stems to help lift the clump but do not pull the tubers out by pulling on the stems. If you do this, you’ll likely break off some of the tubers.

As hard as you try not to damage the tubers, most likely you will impale or damage some of them. But as long as you are working carefully to get under the tubers, most of your dahlia tubers should remain intact.

Step 4: Clean Up the Tubers

Gently brush the dirt off your tubers. If your soil is loose and crumbly, this might take care of the majority of the dirt. You can use your hands, a whisk broom, a paintbrush or even a stick to loosen the soil and remove as much as possible. Set your tubers aside, making sure that the tuber clump is labeled.

Continue to dig up tubers, setting them aside once you’ve cleaned them off a bit. This process will not remove all the dirt from your tubers. You’re trying to remove the majority of the soil.

At some point, you’ll want to wash your tubers to remove the remaining dirt. When you do this will depend on how much time you have available. If you’re just digging up a few dahlia plants, then you could rinse them off now. However, if you have many plants, you might need to do this on separate days. Dig one day and then wash on another day. I like to do all the washing at one time as this is a cold, wet job if you are dealing with a lot of tubers.

Step 5: Storage

The key to healthy long-term storage is to make sure your tubers remain moist enough to not shrivel up but dry enough to not mold. This process is a balancing act.

It is absolutely critical that your tubers are completely dry before you put them into long-term storage. If you’ve washed them off with water, then they will need a place to dry out before you store them. I like to place them loosely in a box in my garage to allow them to dry adequately before storing them. You could also place them in crates, paper bags, or wrap them in newspapers for short-term drying.

It’s best to let them dry for a few days before you store them for the winter. If you don’t allow the tubers time to dry, you risk them getting moldy and losing your whole stash.

Once the tubers have dried adequately, it’s time to store them for the winter. There are many ways to do this. You can store them as a whole clump or you can separate the tubers. For long-term storage, use a lined crate or plastic container to help prevent excess moisture loss. Avoid storing the tubers in cardboard or paper bags as this can wick too much moisture from them.

Here are a few options for storing your tubers…

1. Store whole clumps in peat moss, vermiculite or wood shavings

Line your boxes with peat moss, vermiculite or wood shavings. Peat moss can be difficult to find these days, so vermiculite or wood shavings used for pet bedding make an excellent substitute. Place your tuber clumps into the peat moss, separating them as much as possible. Cover with more peat moss. Add another layer of tubers on top of the first layer, making sure that they are separated from each other with peat moss.

The biggest concern here is to minimize the tuber clumps touching each other. This helps reduce the risk of spreading disease.

2. Divide the tubers and store in peat moss, vermiculite or wood shavings

You can separate the tubers now or wait and separate them in the spring. If you separate the tubers now, be sure to label each tuber. Use a sharpie marker to write what the tuber is directly on the tuber. That way, you won’t get your flowers mixed up. You could also just put each dahlia type in separate boxes. If you don’t have a lot of tubers, this is a perfect option. Be sure to label your boxes with the flower name. If you are dealing with many tubers, then labeling them directly will save on storage space.

3. Divide the tubers and wrap in saran wrap

While this technique seems a little strange, I’ve had good luck with this method for several years. The key to maintaining healthy tubers is to make sure that they had time to adequately dry. Otherwise they can easily mold with this technique.

To use this method, take a single tuber and wrap it completely with saran. Place a second tuber next to the first and roll the saran around it. Place a third tuber in next to the second and wrap it. Usually, I can get about 4-5 tubers in each bundle. The trick is not to let any tubers actually touch each other. Then you can place your bundles in a box. You won’t need peat moss or wood shavings for this method. Since you protected the tubers from moisture loss, you could store the bundles in a cardboard box.

A few key points to keep in mind…

1. Storing your tubers in peat moss, wood shavings or vermiculite is way less time-consuming than wrapping them in saran. However, you’ll need more storage space.

2. If you want to increase the number of dahlias you grow, then dividing the tubers can give you many more plants for next year.

3. You can divide dahlias in the fall or the spring. It really depends on when you have the time available to do the work. If you divide in the spring, the eyes will be a little more obvious.

4. If you’re not sure which method to use, you could try several of these techniques. That way, if you have problems with one technique, you won’t lose all your tubers.

Once you’ve placed all your tubers in boxes or crates, you’ll want to store them for the winter in a cool area that will not freeze. Your protected garage or basement are good options. The best storage temperature is between 40-50 degrees.

Do not store your tubers in an unprotected shed that can freeze, otherwise you could lose all your tubers to cold winter weather.

Step 6: Periodically Check Your Tubers

During the winter months, you’ll occasionally want to check on your tubers. Examine them for mold so you can remove any damaged tubers before they infect the rest of your stash. This helps to prevent disease spreading to the entire box of tubers. I try to check my tubers a few times during the winter months.

How to Divide Your Dahlia Tubers

The first time you divide your tubers can be a little intimidating. But once you get the hang of it, it’s pretty easy. For each viable tuber, you’ll need to have part of the original growth (the crown) with an eye, a viable neck and the body. The growing eyes are on the crown and the neck connects the crown to the body. If your neck is broken, then the body of the tuber cannot supply nourishment to the growing eye. When this happens, the tuber will not be viable.

So be careful to not damage the necks on your tubers. And as hard as it is to do, if you have a tuber with a broken neck, just toss it.

To separate your tubers, you will need a pair of heavy duty clippers, a pair of snips, and possibly a sharp knife and cutting board.

Start by removing the stem and any roots or fine root hairs that are attached. It’s easier to separate the tubers when you have a clean clump. The next thing to do is examine your tubers. Do you see any obvious eyes you want to save? Be aware of those eyes as you cut your clumps apart.

Now is the time to actually divide your clump. Use your clippers or sharp knife to cut the clump in half. Do this by starting at the stem base and cutting through the whole clump.

Next, examine the tubers of one section. Remove any with broken necks or obvious damage. Then use your clippers to separate the tubers. Make sure that each tuber has part of the crown with an eye, a non-broken neck and the body. Set aside each cut tuber and continue working on that section. Then move to the second section and repeat. Once you’ve separated the tubers, be sure to label or mark them so you know what flower it is.

Here is a pictorial on dividing your dahlias from the American Dahlia Society… Cutting Dahlia Tubers. The first time you separate your tubers, you might feel a little unsure of yourself. But over time, it will get easier and pretty soon you’ll be a pro.

While saving your dahlia tubers takes a little time and effort, it’s worth that effort when next spring you can pull out your tubers and plant them. You’ll enjoy the beautiful flowers all over again and you’ll have lots more plants to enjoy.

Once you’re bitten by the dahlia bug, it’s just a natural extension to learn to save your tubers for next year. Digging up your dahlia tubers will become a regular fall chore. So follow these steps to prepare your dahlias for winter. You’ll be glad you did next spring!