Dividing Dahlias in the Fall with Confidence

If your dahlia flower garden burst into color this summer, now’s the perfect time to set the stage for an even bigger bloom next year! Dividing dahlias in the fall not only keeps your plants healthy but also helps you multiply your collection for free. With a little know-how, splitting dahlia tubers and overwintering dahlia bulbs (tubers) can be simple and rewarding. In this guide, you’ll learn how to divide dahlia tubers, the best methods for wintering dahlia bulbs, and essential dahlia care tips to ensure strong growth come spring. These are all things I’ve learned in my three decades of growing dahlias. It’s hard to believe so many years have passed! Let’s dig into propagating dahlias and discover how to separate dahlia tubers the right way for a thriving, colorful garden year after year.

Why I Like to Divide Dahlias in the Fall

Until a few years ago, storing our dahlia tubers took up a lot of room. My dear husband even built some special boxes (pictured further on down) for keeping the tubers ventilated in our moist Oregon climate. Before dividing the tubers in the fall, I used to worry that my tubers wouldn’t fit in the three large boxes. The boxes took up a lot of space in our garage, and were a pain to move out to the garden in the spring for planting. I decided to try to contain all of the dahlia tubers in one box, leaving the other boxes for other purposes. This meant dividing the tubers in the fall. It turns out it’s easier than I expected. Plus, I ended up with extra tubers to give away to grateful friends. If you are hesitant to divide your dahlia tubers in the fall, read on for some examples, simple steps, and easy tips for success!

Advantages of Dividing Dahlia Tubers in the Fall

One big advantage to dividing dahlia tubers in the fall is the clumps of tubers are soft and pliable. They come apart easily. If you get a good grip on the stalks where they emerge from the tubers, you can sometimes pull the tuber clumps apart with minimal effort. Sometimes the tubers separate with no effort at all. So, why wouldn’t everyone divide dahlia tubers in the fall if it’s so easy? Well, there is another side to the story.

Disadvantages of Dividing Dahlia Tubers in the Fall

Where I live, fall is often cold and rainy. By the time I get around to digging up the tubers, the ground is usually muddy. The dahlia tubers are wet, messy, and tough to label. It might be difficult to find a spot to clean the dahlia tubers, since it can make a huge muddy mess. We usually have to set our tubers in a dry spot, like the garage, on a tarp after cleaning. (But we would do that anyway, dividing or not.) Sometimes, people would rather just dig up the dahlia tuber clumps and toss them in a box, waiting until spring to see eyes forming before dividing. Totally understandable!

How to Dig, Divide, Label, and Store Dahlias in the Fall

Where I live, in USDA plant hardiness Zone 8b, some dahlias do survive in the ground without digging, but there is always the danger of rotting in the ground. Even when we have a mild winter, most of our flower beds stay too moist for the dahlias to remain under the soil. I do keep a few dahlias in the ground all year in a sunny spot by our orchard, but they are hardy tubers that I don’t care about as much. That seems insensitive, but I do have my favorites!

When do you dig up dahlias?

When your dahlias look like the picture below, it’s time to dig them up.

Another good guide is to determine if the tubers have been in the ground for at least 120 days. If so, then you are okay to dig. I always tell myself that I will make notes about each dahlia before they get to this point. I would like to write down the characteristics of each bloom, whether it’s good for cutting, and whether I need to give some of the tubers away. Now that I have a handy garden planner notebook, I have been doing better with this! The past couple of years, our first freeze has taken place around Veteran’s Day. Even if a hard freeze hasn’t come yet, by that time the dahlias have been in the ground well over 120 days, so it’s fine to dig them up.

Cutting the Stalks of the Dahlias

To cut the dahlia stalks, I have to use a heavier tool than a hand pruner. Some of the stalks are as big around as a silver dollar. For heavier cutting, I use some loppers, like this pair.

When I lop off the stalks, I leave a few inches of the stalk, or stalks, above the ground. That way, I have something to tie the labeling tape onto. Before labeling, I have to get those tubers out of the ground. Most years, the day that I dig the dahlia tubers is wet and soggy. This year, the weather was gorgeous.

Labeling the Dahlia Tubers When Digging

Since the tubers are covered in dirt, I can’t write on them. I have to tie something around the stalks to label them and keep them in order. I like to use flagging tape. Sometimes it’s pink, sometimes it’s green. I like it because it’s easy to cut or tear, and I can write on it with a permanent marker.

This year, I tried something new. Using my garden notebook, I looked at my dahlia tuber layout and wrote on strips of flagging tape before digging up the tubers. I kept the tape strips in order by rows, then tied the labels on the tubers after the stalks were cut. It was so much faster! Keeping track of my dahlia layout in a garden notebook is the way to go!

Here is one of the plants after labeling. I can clearly see which dahlia it is, so there will be no confusion.

My favorite pen to use for marking is a handy one for gardeners. It’s a retractable Sharpie marker, and it’s a great thing to have when my hands are grubby. I don’t want to be messing around with capping and uncapping a pen, so this works really well. I can store it in the pocket of my jacket without worrying about it marking anything.

Digging Up the Tubers

Once the stalks are cut off, I use a large round shovel to dig around the plant. Some people use a pitchfork. I try to stay at least one foot away from the stalk so I don’t accidentally slice into a tuber. When the soil is loosened, I use the stalk to lift the mass of tubers slightly, then I place my hands down in the dirt to lift the bundle of tubers out of the dirt. I set the tuber bundle beside the hole and fill it in. 

If you have a large clump of tubers you want to divide before hefting out of the ground, you can use a gardening tool like a dandelion weeder to gently pry the tubers apart. In the photo below, I used this method (along with my trusty kneeling pad) and ended up with four tubers from the one clump. You can do this initial dividing if you have a large, unwieldy, heavy clump to make it more manageable for dividing further once it is cleaned off. Note: Now that I am so faithful about dividing the dahlia tubers each year, I hardly ever have huge clumps anymore. It’s wonderful!

How Do You Get All of the Dirt Off?

Where I live, in the rainy Pacific Northwest, our ground is damp and our clay soil sometimes clings to the tubers like glue. I take the wheelbarrow full of tubers to a spot in our front field and hose them off. It is a messy process, but it makes a huge difference, as you can see below.

Thank goodness I have an old waterproof farm coat I found at a secondhand store years ago. You can also wear rain gear, as detailed in this post about what to wear when gardening in wet weather.

Letting the Tubers Dry Out

After being rinsed, the tubers go back into the wheelbarrow. I take them to our garage and set them on a tarp to dry for a day. Since our climate is damp, I could even let them dry for a few days, depending on the weather. The important thing is not to let your tubers get too dry and shriveled up.

Supplies Needed for Dividing the Dahlia Tubers

In addition to the large tarp, I employ a few basic supplies for dividing the tubers. Here they are:

1 pair of scissors for snipping the roots

1 set of pruners for trimming the stalks and the crowns (my favorite kind are made by Felco)

1 foldable hand saw for cutting through tough dahlia tuber clumps

1 pair of garden gloves to protect your hands from the cutting tools (I take mine off and on quite a bit during the process.)

Sharpie or slightly dull ink pencil for writing on tubers

Paper bags or containers for organizing tubers to give away (optional)

Bucket, bowl, or large cup with 1 part bleach to 9 parts water to sanitize tools between clipping each tuber. (If you are worried about your garden tools rusting, rinse and thoroughly dry your tools immediately after you have finished the dividing process.)

Bowl of cinnamon for dusting on the open cut areas of tubers for protection from disease (optional)

Cardboard or wooden box for storing dahlia tubers over the winter

Vermiculite or wood shavings for packing loosely around the dahlias for storage (Some people wrap their tubers in plastic wrap, but I never have. Some also use shredded paper as a storage option, and I address that further on down.)

How Do You Separate Dahlia Tubers for Winter Storage?

Once the tubers are clean and have dried for a day (you don’t want the tubers to dry out too much), they are ready to be divided for winter storage.

When you are handling the dahlias, some of the clumps may come apart and sort of divide themselves. As long as you have a stalk coming out of each divided tuber (or tuber cluster) you know you have a viable dahlia. That’s how easy it is to divide the tubers in the fall. You just don’t have any eyes on the tubers to guide you. If some of the tuber clumps come apart, just make sure to label each dahlia so you don’t have any mysteries.

Here are some common dahlia-dividing scenarios you may encounter, with tips for each situation.

Easiest Dahlia Dividing: Wiggling and Prying

In the top portion of the photo you can clearly see the two dahlia stalks or stems intertwined. Without needing any special garden tools, just grasp the stalks near the base and gently wiggle the tubers apart. Use your fingers (the most effective gardening tools) to pry apart the two parts of the dahlia tuber clump. When the clusters separate, you can proceed with trimming the stem down closer to the crown for storage. If I have room in the dahlia storage box, I sometimes leave the stems. The tags sticking out of the ground when planting in the spring are helpful markers to me.

Easy Dahlia Dividing: Cutting Through the Crown

When you have multiple tubers growing out of a single dahlia crown (where the tubers come together below the stem), you can often cut right through the crown with the garden pruners. As long as you leave part of the crown connected to the neck of the tuber, you should have some eyes appear in the spring. The tubers above could be divided further, but since I’m not sure of where the eyes are, and I have room in the storage box, I will keep these connected.

Dividing Difficult Clumps: Sawing Through Thick Tuber Clumps

As much as I try to divide regularly to avoid ending up with massive clumps of tubers, sometimes it happens. This variety, Midnight Moon, had a particularly prolific year. The tubers multiplied amazingly well. When this happens, I reluctantly get out the hand saw. Some people even use a battery-powered oscillating tool for this approach. 

I cut in between the stems, prying the clump carefully apart as I go, separating the large tuber clump into smaller tuber bundles that are easier to work with. It seems like a brutal approach, but it’s effective. If I had two hours to work on one tuber clump, I might try to snip, snip, snip away at the clump, working from the top down. I don’t have that kind of time, though.

Once the tubers are separated into smaller clusters, then I can use he pruners to cut each tuber apart from the clump, making sure that each tuber has a neck and piece of the crown to go along with it. 

Labeling the Dahlia Tubers After Dividing

When dividing dahlias into individual tubers, you will need to write on the dahlia tubers themselves. To do this, you can use a Sharpie or an ink pencil. Make sure the dahlia tuber is clean and dry (as much as possible). I have found that writing on tubers with an ink pencil works best if the pencil is slightly dull.

Cleaning Up and Giving Away Extra Dahlia Tubers

When dividing dahlias in the garage, I’m careful to work on top of a tarp. That way, when I’m done, cleanup is easy. I just gather up the edges of the tarp with all of the dirt and leftover plant material, bundle it together, and take it outside.

When I am labeling tubers to give away, I sometimes don’t have time to write on each individual tuber. I sort the tubers into labeled paper bags by type, then let people do their own labeling when they take tubers for themselves. I usually provide extra bags and Sharpie markers so people can mix and match to create their own custom collection. The dahlia tuber give-away has become a popular event where I work. During the most recent give-away, the tubers were snapped up right away, and I didn’t even have to do any cleanup. It was great!

Over-Wintering Dahlias

What is the best way to store dahlia tubers? Can you store dahlia tubers in sawdust? As previously noted, we usually store our tubers in wood shavings, since we have a good supply from projects. One of our friends, an avid dahlia-lover, assures us that packing the dahlias in vermiculite is the best way to over-winter the tubers.

Further on down I give details about storing dahlias in shredded paper, if that is what you have to work with.

Dahlia Storage Boxes

This past winter, my husband constructed some amazing, stackable dahlia storage boxes. As you can see in the photo below, the boxes have ventilation holes. To keep packing material from escaping, a piece of thin wire mesh is attached to the inside of each side of the box. Genius!

He made three boxes for me, but now I only need to use one for dahlia storage. We use the others for storing our potato harvest and onion harvest in separate boxes.

Whatever packing method you choose, make sure you find a spot that’s not too cold. We stored our tubers in our garden shed one winter and lost them all, due to cold temperatures. Now we store our tubers in boxes in the garage, and that has worked well for the past ten years.

Common Questions About Dividing and Storing Dahlia Tubers in the Fall

What happens if you don’t divide dahlias?

Do you have to divide dahlia tubers? Economically, it makes sense to divide dahlias. Over the years, with repeated dividing, you can get many lovely dahlias for the price of one tuber. In addition to propagating the dahlias for your own garden, you might like to divide dahlias to have some plants to share. In my experience, the plants that grow from divided tubers are healthier. We have a row of dahlias that have not been divided. They grow in soil that is hard and rocky.  Years ago, we decided to just leave them where they are just to see what would happen. Most of them do come back every year, but they are less colorful and vigorous-looking than their counterparts that have been divided.

 

Should I wash dahlia tubers before storing?

There are different opinions about this. Some prefer not to wash dahlia tubers before storing them for the winter. Dahlia tubers have a natural protective coating that helps prevent rot and fungal growth during storage. Washing the tubers can remove this protective layer, making them more susceptible to issues during the storage period.

However, washing may be necessary if the tubers are seriously dirty or contaminated with soil or debris, as in the case of our tubers. If you choose to wash your dahlias like we do, it should be done carefully to avoid damaging the protective skin. 

Can you store dahlia tubers in an unheated garage?

Yes, you can store dahlia tubers in an unheated garage, as we do, as long as you take certain precautions to ensure they are protected from freezing temperatures. Storing dahlias in an unheated garage can be a suitable option for winter storage if the garage maintains temperatures above freezing but below 50°F (10°C).

Can I store dahlia tubers in shredded paper?

Storing dahlia tubers in shredded paper can be a suitable option as long as you take certain precautions to ensure the tubers remain dry and protected from rot. Shredded paper can serve as an insulating and moisture-absorbing medium. Here’s how you can do it:

Prepare Shredded Paper: Shred newspaper or plain, uncolored paper into small pieces. Ensure that the paper is clean and dry. You can also use straw or dry leaves as an alternative to shredded paper.

Layer Tubers and Shredded Paper: Place a layer of shredded paper in the bottom of the storage container. Lay the tubers on top of this layer, leaving some space between them. Gently cover the tubers with more shredded paper, ensuring they are completely surrounded but not buried.

Can you store dahlia tubers in plastic bags?

Storing dahlia tubers in plastic bags is possible, but it comes with some considerations and potential risks. Plastic bags can trap moisture, which can lead to rot if not managed properly. If you choose to store dahlia tubers in plastic bags, here’s how to do it:

Choose Plastic Bags: Use clear, breathable, and well-ventilated plastic bags, such as zipper-seal bags with small holes or perforations. Avoid airtight or non-breathable bags, as they can trap moisture and lead to fungal issues.

Place Tubers in Bags: Group the tubers together by variety or size and place them in the plastic bags. Make sure the tubers are clean and dry before placing them in the bags.

Add Insulating Material: To help protect the tubers from extreme temperature fluctuations, you can add an insulating material such as dry wood shavings, vermiculite, or shredded newspaper to the bags. This helps maintain stable humidity levels.

Seal Bags Loosely: Seal the plastic bags loosely to allow for some airflow. This will help prevent excessive moisture buildup inside the bags.

Wondering What to Wear When Dividing Dahlias?

There is no guarantee that the weather will be nice when dividing dahlias. Whether you divide them in the spring or fall, how can you be prepared no matter what the weather holds? Get some tips about what to wear for gardening in any type of weather!

Unique Gifts for Dahlia Lovers

Looking for the perfect dahlia gift for someone? If you have a dahlia-lover in your life, here are some fun gift ideas. Show an affection for dahlias with these creative dahlia-themed gifts.

   

Dahlias: Beautiful Varieties for Home & Garden	Especially for those who enjoy growing these prolific summer-blooming plants. This book can help ease the off-season blues.
Kate Spade New York Foldable Reusable Shopping Tote	Use this foldable bag time and again to add a splash of color to a shopping trip. Lightweight and packable!
Pop-up Dahlia Flower Greeting Card	The perfect card for a dahlia-lover on Mother’s Day or a birthday, this pop-up card is a day-brightener.
Painted Dahlias Stainless Steel Tumbler with Lid	This unique, pretty 30-ounce tumbler is insulated to keep a drink hot or cold for up to 24 hours.
Double Layer Inverted Dahlia Print Umbrella	Show your love of dahlias with this waterproof, windproof, UV protector umbrella with a colorful print of a dahlia bloom.

 

Referring Back to My Garden Planner Notebook

A few years ago, as a result of needing to keep track of what kind of dahlia we planted where, I decided to begin a garden planner notebook. I planned to have tasks and notes for each month. I sort of kept up with it. One thing I definitely included in the notebook was the list and description of each dahlia variety we owned at the time. Now that we have a few more varieties, thanks to our generous gardening friend, I’m going to add them to the list as well. If a garden planner notebook seems like a good idea to you, good news! I added the 16 master pages to the free resource library for subscribers to the Fluxing Well blog.

Get the garden planner!

Free Online Garden Planner Layout Template

Now that you know how to divide dahlia tubers, you might need a way to plan your dahlia bed layout. This online garden planner can help you visualize your design and bring it to life. With garden tasks that need your attention, this is one way to save time.

It’s fully customizable when you make your own copy and includes two editable chart pages for noting planting specifications.

Get my free online garden layout planner template!

What About Your Dahlia Experiences?

I hope this has helped you to learn how to divide dahlia tubers in the fall. Have you had prior dahlia experience? Do you have any favorite tricks to share? If you take the time to give me a tip, I’ll even write it down in my garden notebook or maybe add your advice to this post. We all do better when we share what has worked well.

Other Gardening Posts You Might Enjoy

Do you struggle with knowing what to plant in flower containers? Get some great flower container ideas you can use, even if you’re artistically challenged. Learn about easy-care perennials and fabulous flowering shrubs. Get some easy tips for growing fragrant old garden roses or make your own DIY pole bean tower. If you are looking for simple, low-maintenance gardening tips, I’m here for you!

Have a wonderful week, and may all of your fall dahlia dividing endeavors meet with success!

Lisa Mitchell is a wife, mom, and school librarian who likes to grow fruit, vegetables, and flowers on her family’s small Pacific Northwest farm. To learn more about what this website has to offer gardeners, click on over to the Garden page.

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