Introduction
There is a special kind of magic in the late-summer garden when dinnerplate dahlias take center stage. Their vibrant colors and intricate petal patterns provide a spectacular finale to the growing season, often blooming right up until the first frost. At Longfield Gardens, we believe that the joy of growing these stunning flowers should not end when the weather turns cold. Because dahlias are tropical plants native to Mexico, they cannot survive freezing soil, but that does not mean you have to buy new ones every year.
Learning how to store dahlia tubers through the winter is one of the most rewarding skills a gardener can develop. By lifting and protecting these tubers during the dormant season, you can enjoy your favorite varieties for years to come. This process also allows your dahlia collection to grow, as a single tuber planted in the spring often multiplies into a large clump by autumn. This guide is designed to help home gardeners of all levels successfully navigate the transition from a blooming summer garden to safe winter storage. For a broader growing overview, see our All About Dahlias guide.
With a few simple tools and a little bit of space in a cool corner of your home, you can ensure your dahlias return even stronger next year. Protecting your investment in your garden is simple, effective, and deeply satisfying. If you want to start bigger next spring, our Bulk Buys for Spring page is a good place to look.
Knowing When to Dig Your Dahlias
The most important factor in a successful winter storage plan is timing. Dahlias need a full growing season to develop the energy-rich tubers required for next year’s growth. If you dig them too early, the tubers may be thin and prone to shriveling in storage. If you wait too long, a deep freeze could damage the "eyes" of the tuber, which are the points where next year's stems will emerge.
In most parts of the United States, the ideal time to dig dahlia tubers is shortly after the first frost. You will notice that the lush green foliage turns black or dark brown almost immediately after a freezing night. While the plants look a bit sad at this stage, this is a positive sign for the tubers. The frost sends a signal to the plant to enter dormancy, and the remaining energy in the stalks begins to move down into the root system.
If you live in an area where frost comes very late, or if you want to get a head start on your garden cleanup, you can usually dig the tubers once the plants have been in the ground for about 120 days. However, waiting for that first light frost is the most reliable way to ensure the tubers are fully "cured" and ready for a long winter sleep.
Key Takeaway: Wait for the first frost to turn the foliage brown before digging. This ensures the tubers have maximized their energy storage for the following spring.
Preparing for the Harvest
Once the foliage has turned brown, it is helpful to wait a few days—up to a week—before you start digging. This brief waiting period allows the "skin" on the tubers to toughen up slightly, making them less susceptible to nicks and scratches during the moving process.
Before you reach for your garden fork, take a moment to label your plants. Once the flowers are gone and the leaves are brown, it is almost impossible to tell a Café au Lait dahlia from a "Thomas Edison" variety. Use waterproof tags or garden markers to identify each plant. You can tie the tags directly to the base of the stems.
After labeling, cut the stalks back to about 4 to 6 inches above the ground. This leaves you with a sturdy "handle" to hold onto while you are lifting the clump, but removes the bulk of the dead foliage. Use sharp, clean bypass pruners for this task. Because dahlia stems are hollow, they can sometimes hold water; cutting them back a few days before digging allows some of that moisture to evaporate.
How to Dig Dahlia Tubers Safely
Digging dahlia tubers requires a gentle touch. The necks of the tubers—the narrow part that connects the tuber body to the main stalk—are quite fragile. If a neck breaks or cracks, the tuber may not be able to sprout next year.
The best tool for this job is a sturdy garden fork rather than a shovel. A fork allows you to lift the soil and the tubers while letting excess dirt fall through the tines, and it is less likely to slice through a tuber than a solid spade blade.
- Start Wide: Position your garden fork about 12 inches away from the main stem. Dahlias often grow outward as much as they grow downward, and you want to avoid spearing the tubers.
- Loosen the Soil: Gently push the fork into the ground and rock it back and forth. Move in a circle around the plant, loosening the soil on all sides.
- Lift Gently: Once the soil is loose, slide the fork deep under the center of the clump and lift upward. Use your other hand to grasp the stem "handle" you left behind and help guide the clump out of the earth.
- Shake Off Excess Dirt: Gently shake the clump or use your fingers to remove the heaviest clods of soil. Do not bang the tubers against each other or against the fork, as this can cause bruising.
What to Do Next
- Double-check that the label is still attached to the clump.
- Check for any tubers that were accidentally sliced; these should be removed as they are prone to rot.
- Place the clumps in a shaded, dry area like a garage or a porch for a few hours.
Cleaning and Curing the Tubers
Once your tubers are out of the ground, you have a choice: to wash them or not. Both methods have successful followers, and the right choice often depends on your soil type.
If you have heavy clay soil, washing the tubers is usually the best approach. Clay can trap moisture against the skin of the tuber, which may lead to rot during the winter. Using a garden hose with a gentle spray nozzle, wash away the soil until the tubers are clean. This also makes it much easier to see the "eyes" if you plan on dividing the clumps before storage.
If you have very sandy, well-draining soil, you might prefer to simply brush off the dry dirt once the tubers have sat for a few hours. Some gardeners believe the residual soil acts as a natural insulator and helps prevent the tubers from drying out too much.
Regardless of whether you wash them, the tubers need to "cure" before they go into their final storage containers. Curing is simply the process of letting the tubers dry out so the outer skin can firm up. Place the tubers in a frost-free, well-ventilated area—like a basement or a cool garage—away from direct sunlight. Turn them upside down so that any water trapped in the hollow stems can drain out. Usually, 24 to 48 hours is enough time for the surface of the tubers to feel dry to the touch. For a full winter-storage walkthrough, see How to Store Dahlia Bulbs.
The Anatomy of a Viable Dahlia Tuber
To understand how to store dahlia tubers through the winter, it helps to know what a healthy tuber actually looks like. Not every root in the clump is capable of growing a new plant. A viable dahlia tuber must have three specific parts:
- The Body: This is the fat, potato-like part of the root. It stores the energy and nutrients the plant will need to start growing in the spring.
- The Neck: This is the narrow section that connects the body to the crown. It must be intact and firm.
- The Crown (with an Eye): The crown is the area at the top of the neck where it meets the old stalk. This is where the "eyes" are located. An eye is a small bump or bud that will become next year's stem.
If a tuber is missing any of these three parts, it will not produce a flower. A fat tuber with a broken neck is useless, and a crown without a tuber body has no energy to grow. When you are cleaning and inspecting your harvest, look for these three components to ensure you are only saving the best stock.
To Divide Now or Later?
One of the biggest debates among dahlia enthusiasts is whether to divide the clumps in the fall or wait until the spring. Dividing simply means cutting the large clump of tubers into individual pieces, ensuring each piece has a viable eye. For a step-by-step look, see our How to Divide Dahlia Tubers guide.
Dividing in the Fall
The main advantage of dividing in the fall is that the tubers are relatively soft and easy to cut. You also save a significant amount of storage space because you aren't storing the "mother tuber" (the original one you planted) or any damaged pieces that won't grow. The downside is that the eyes can be very difficult to see in the fall when the plant is dormant.
Dividing in the Spring
Many gardeners prefer to store the clumps whole and divide them in the spring. By March or April, the eyes begin to swell and may even turn pink or green, making them very easy to identify. However, the tubers can become quite tough over the winter, sometimes requiring a bit more muscle to cut.
If you are a beginner, we recommend storing the clumps whole or in large chunks. This reduces the risk of accidentally cutting off the eyes and gives you more flexibility when planting time arrives.
Choosing a Storage Medium
Dahlia tubers are like Goldilocks: they don't want to be too wet, or they will rot, and they don't want to be too dry, or they will shrivel and die. The "storage medium" is the material you pack around the tubers to help maintain that perfect balance of moisture.
There are several effective options you can use:
- Peat Moss: This is the most common choice. It is affordable and does a great job of cushioning the tubers while absorbing excess moisture. Many gardeners lightly mist the peat moss so it is barely damp (like a wrung-out sponge).
- Vermiculite: This mineral is excellent for storage because it is sterile and resists mold. It provides a very consistent environment for the tubers.
- Wood Shavings: Cedar or pine shavings (often sold as animal bedding) provide good air circulation and have natural antifungal properties.
- The Plastic Wrap Method: Some gardeners wrap individual, cleaned tubers tightly in plastic kitchen wrap. This seals the moisture inside the tuber itself. While effective, it requires the tubers to be perfectly clean and dry on the surface to prevent mold from being trapped inside the wrap.
Once you have chosen your medium, place a layer of it in the bottom of a container—such as a cardboard box, a plastic bin with a few air holes, or a wooden crate. Lay the tubers or clumps in the container so they aren't touching each other, then cover them completely with more of the medium.
Key Takeaway: The goal of your storage medium is to prevent the tubers from shriveling while allowing enough air circulation to prevent rot.
The Ideal Storage Environment
Where you keep your containers is just as important as how you pack them. The ideal temperature for dahlia storage is between 40°F and 50°F.
If the temperature stays above 50°F, the tubers may think it is springtime and start to sprout prematurely. If the temperature drops below freezing, the water inside the tubers will freeze, causing the cell walls to burst and turning the tuber into "mush" once it thaws.
Good storage locations include:
- An unheated basement or crawl space.
- A cool closet in a mudroom or entryway.
- An insulated garage (provided it stays above freezing).
- A root cellar.
Avoid storage spots near furnaces, water heaters, or large windows where temperatures can fluctuate wildly. Consistency is key to keeping the tubers in a deep state of dormancy.
Checking Your Tubers Mid-Winter
Storing dahlias isn't a "set it and forget it" task. We recommend checking on your tubers about once a month throughout the winter. This allows you to catch small issues before they become big problems.
During your monthly check, look for two things:
- Signs of Rot: If you see a tuber that has turned black, soft, or fuzzy with mold, remove it immediately. Rot can spread quickly from one tuber to another, so taking out the "bad apple" can save the rest of your collection.
- Signs of Shriveling: If the tubers look wrinkled or feel light and hollow, they are losing too much moisture. You can remedy this by lightly misting the storage medium with a spray bottle of water. You don't want it wet—just slightly damp to the touch.
If you find that your storage area is consistently too dry, you can try placing the cardboard boxes inside a large plastic trash bag, leaving the top of the bag open to allow for some air exchange.
Preparing for Spring Planting
As the days grow longer and the soil begins to warm, your dahlia tubers will naturally start to wake up. You may see small sprouts beginning to emerge from the eyes. This usually happens in late March or April.
A few weeks before your last frost date, you can move the containers to a slightly warmer spot to encourage more active sprouting. This is also the perfect time to divide any clumps you stored whole. If you notice any tubers that didn't make it through the winter, don't be discouraged. Even professional growers expect a small percentage of loss.
When the soil temperature reaches about 60°F and the danger of frost has passed, your stored tubers are ready to go back into the garden. You'll find that these "veteran" tubers often grow faster and bloom earlier than brand-new ones, as they already have a established energy reserve.
Conclusion
Storing dahlia tubers through the winter is a simple and rewarding way to expand your garden and protect the plants you love. By following the steps of waiting for the frost, digging carefully, and providing a cool, stable environment, you can ensure a vibrant display of color year after year. While it may seem like a lot of steps at first, most gardeners find that the process quickly becomes a favorite autumn ritual—a way to say goodbye to the current season while already planning for the next. If you’re thinking about starting fresh next season, browse our New Dahlia Collections.
At Longfield Gardens, we take pride in providing high-quality tubers like Thomas Edison that are ready to perform in your garden. Whether you are starting with new varieties or preserving your favorites from last year, the result is the same: a stunning, flower-filled landscape that brings joy to you and your neighbors.
- Wait for the foliage to turn brown before digging.
- Keep the "eye, neck, and body" intact for every tuber you save.
- Store in a cool (40–50°F), dark place in a medium like peat moss or vermiculite.
- Check monthly for rot or shriveling to ensure winter success.
Storing your own tubers is the best way to turn a small garden into a lush, flower-filled oasis. With just a little bit of winter care, your dahlias will reward you with even more spectacular blooms next summer.
The next step is easy: take a look at your garden, identify your favorite dahlias in our Dahlia Collections, and get your labels ready for the first frost. You’ll be amazed at how simple it is to keep the beauty of summer alive all winter long.
FAQ
Can I leave my dahlia tubers in the ground if I mulch them heavily?
In USDA zones 8 and warmer, you can often leave dahlias in the ground with a thick layer of mulch for protection. However, in zones 7 and colder, the ground typically freezes deep enough to kill the tubers regardless of mulch. For these colder climates, lifting and storing them indoors is the only reliable way to ensure they survive the winter. If you’re unsure about your climate, the Hardiness Zone Map can help.
What should I do if my dahlia tubers have mold on them during storage?
If you find a small amount of surface mold, wipe it off with a cloth dipped in a weak solution of water and white vinegar or a fungicide. Make sure to let the tuber dry completely before putting it back. If the tuber is soft or smells foul, it has begun to rot and should be thrown away immediately to prevent the mold from spreading to healthy tubers.
Do I need to treat my dahlia tubers with a fungicide before storing?
While not strictly necessary, many gardeners choose to dust their tubers with sulfur powder or a garden fungicide after cleaning and before packing them away. This can provide an extra layer of protection against rot, especially if you live in a very humid climate or have had issues with mold in the past.
How long can dahlia tubers stay in storage?
Dahlia tubers can stay in dormancy for about 4 to 6 months, which is usually the length of a standard winter. If they are kept in the ideal temperature range of 40–50°F, they will remain dormant until you bring them out into the warmth of spring. If they stay in storage much longer than six months, they may eventually exhaust their energy reserves and fail to sprout.
