Introduction
Dahlias are the undisputed grand finale of the summer garden. As other flowers begin to fade in late August and September, these spectacular plants find their second wind, offering a kaleidoscope of colors and shapes until the very last moment of the season. At Longfield Gardens, we believe the only thing better than a dahlia in full bloom is knowing you can enjoy that same beauty again next year. Because dahlias are tropical plants, they need a little extra care to survive the cold winter months in most parts of the United States.
Learning how to winter dahlia bulbs—more accurately called tubers—is a rewarding skill that allows you to build a permanent collection of your favorite varieties. Whether you are growing dinnerplate dahlias with blooms the size of a dinner plate or petite pompon types, the overwintering process is straightforward and achievable for any gardener. By following a few simple steps to lift, clean, and store your tubers, you can keep your plants healthy and ready for a fresh start in the spring. Browse our Dahlia Collections to plan ahead.
This guide will walk you through the entire process of protecting your dahlias during their winter dormancy.
Knowing When to Begin the Process
Timing is the most important factor when it comes to successfully wintering dahlia tubers. If you dig them too early, the tubers may not have stored enough energy to sprout next year. If you wait too long, a deep freeze could damage the crown of the plant. The goal is to let the plant finish its natural growth cycle so it can go into dormancy prepared for the long winter ahead. For a step-by-step reference, see How to Lift and Store Dahlia Bulbs.
In most regions, the signal to start is the first "killing frost." This occurs when temperatures drop enough to turn the dahlia's lush green foliage into a dark brown or black color. While it might look a bit sad to see your vibrant plants wilt, this is actually a helpful part of the process. The cold snap tells the plant to stop sending energy to the leaves and flowers and instead focus all its resources on the underground tubers.
Once the foliage has blackened, we recommend waiting about one to two weeks before you start digging. This short waiting period allows the "eyes"—the small bumps where next year’s growth will emerge—to become more visible. It also allows the skin on the tubers to begin toughening up, which makes them less likely to be damaged during handling. If you live in a climate where a hard frost doesn't occur until very late in the year, you can simply cut the plants back in mid-November to initiate the dormancy period.
Preparing the Plants for Lifting
Before you reach for your shovel, you need to clear the way. Start by cutting the dahlia stems down to about 4 to 6 inches above the soil line. Leaving a short "handle" of stem is very helpful. It gives you something to hold onto while you lift the clump, and it makes it much easier to identify which end is the top when it comes time to store or replant them.
It is also a great idea to label your dahlias during this step. Once the flowers are gone and the stems are cut, most dahlia tubers look remarkably similar. You can use a waterproof garden marker to write the variety name directly on the stem or attach a plastic tag with a bit of twine. This ensures that when you go to plant your garden next spring, you’ll know exactly which colors and heights you are placing in each spot. If you prefer smaller, more compact blooms, browse our PomPon Dahlia collection.
What to do next:
- Monitor your local weather forecast for the first frost.
- Gather your labeling supplies, such as waterproof pens and tags.
- Use garden loppers or hand pruners to cut stems down to 6 inches.
- Ensure each plant is clearly identified before the stems are removed.
Digging the Tubers with Care
The roots of a dahlia are shaped somewhat like a bunch of carrots or sweet potatoes. They spread out horizontally from the main stem, which means they can be wider than you might expect. To avoid slicing through the tubers, you should start digging about 12 inches away from the center of the plant.
We recommend using a garden fork rather than a pointed shovel. A fork allows the soil to fall through the tines and reduces the risk of accidentally cutting into the tubers. Gently loosen the soil all the way around the plant, lifting the fork slightly to feel where the resistance is. Once the soil is loose, reach under the clump with the fork and pry it upward while holding the stem handle you left earlier.
As you lift the clump, you will likely see a large mass of soil clinging to the roots. Give the clump a gentle shake to remove the heaviest pieces of dirt. Be careful during this stage, as the "necks" of the tubers—the narrow part that connects the tuber body to the main stem—can be quite fragile. If a tuber breaks off and loses its connection to the stem, it may not be able to grow a new plant next year.
Cleaning and Curing the Tubers
Once the tubers are out of the ground, they need to be cleaned before they go into storage. There are two schools of thought on cleaning: the "dry" method and the "wet" method. Both work well, and the choice often depends on your soil type. For more tuber basics, see Dahlia Tubers: What You Need to Know.
If you have light, sandy soil, you can usually let the tubers sit in a shady, dry spot for a few hours. The soil will dry out and crumble away with a light brush of your hand. If you have heavy clay soil, the dirt often sticks like glue. In this case, it is better to use a garden hose to gently wash the soil away. A soft stream of water is best; avoid high-pressure nozzles that could tear the thin skin of the tubers.
After cleaning, the tubers must be "cured." This is a simple but vital step. Place the tubers in a frost-free, well-ventilated area for two to three days. A garage, a shed, or a covered porch works perfectly. Turn the clumps upside down so any water trapped inside the hollow stems can drain out. Curing allows the outer skin to dry and harden slightly, which acts as a protective barrier against rot and dehydration during the winter months.
Key Takeaway: Curing your dahlia tubers for a few days in a dry, frost-free location is the best way to prevent rot during winter storage.
To Divide or Not to Divide?
One of the most common questions gardeners ask is whether they should divide their dahlia clumps in the fall or wait until the spring. At Longfield Gardens, we find that both methods have their advantages.
Dividing in the fall is often easier because the tubers are soft and the soil is already on your mind. It also takes up much less storage space. If you have a large collection, storing individual tubers in small bags is much more efficient than storing giant clumps. However, the "eyes" of the dahlia can be very difficult to see in the autumn. These eyes are the growth points located on the "crown" of the tuber, which is the area where the tuber meets the stem.
If you wait until spring to divide, the eyes will have started to swell and may even be turning pink or green. This makes it much easier for a beginner to see exactly where to make the cuts. If you decide to store the entire clump, just make sure you have enough storage material to cover the larger volume.
If you do choose to divide, use a clean, sharp pair of floral snips or a small knife. Each division must have three things to be successful: a body (the tuber), a neck (the connection point), and at least one eye (on the crown). If any of these pieces are missing, the tuber will not produce a plant.
Choosing the Right Storage Material
The goal of winter storage is to keep the tubers in a "Goldilocks" state: not too wet and not too dry. If they are exposed to too much moisture, they will rot. If they are kept in bone-dry air, they will shrivel up and become "mummified," losing the energy they need to sprout.
To achieve this balance, we use packing materials that help regulate humidity. Some of the best options include:
- Coarse Vermiculite: This is a mineral that holds onto just enough moisture to keep the tubers plump without being wet.
- Peat Moss: A classic choice, though it can be a bit dusty. It provides excellent insulation.
- Wood Shavings: The kind sold for pet bedding is inexpensive and works very well to provide air circulation.
- Clean Sand: This is a heavier option but is great for keeping tubers cool and dry.
Avoid using airtight plastic containers without any ventilation. We prefer using cardboard boxes, paper bags, or plastic bins with the lids left slightly ajar. You can layer the tubers like lasagna: put a layer of storage material on the bottom, add a layer of tubers (making sure they don't touch each other), and then cover them with more material.
Finding the Ideal Storage Location
The environment where you keep your dahlia tubers is just as important as the material they are packed in. Dahlias need a spot that stays consistently cool but never reaches freezing temperatures. The ideal temperature range is between 40°F and 50°F.
A cool, dark basement is often the best spot in a typical home. If your basement is heated and stays too warm, an unheated garage or a root cellar might be better options. Just be sure to monitor the temperature in a garage; if it drops below freezing, the water inside the tubers will freeze, causing the cells to burst and the tuber to die.
Humidity also plays a role. If your storage area is very dry, you may need to check the tubers more often to ensure they aren't shriveling. If the area is damp, you’ll need to ensure there is enough airflow to prevent mold from growing on the surface of the tubers.
What to do next:
- Select a storage container like a cardboard box or a breathable bin.
- Purchase your storage medium (peat moss or vermiculite).
- Find a location in your home that stays between 40°F and 50°F.
- Check the tubers once a month to ensure they remain firm and healthy.
Wintering Dahlias in the Ground
If you live in USDA hardiness zones 8, 9, or 10, you may not need to dig your dahlias at all. In these warmer climates, the ground rarely freezes deep enough to harm the tubers. Instead of lifting them, you can winter your dahlias right where they are.
For in-ground wintering, cut the stems back as usual. Then, apply a thick layer of mulch over the top of the planting area. Use 4 to 6 inches of straw, wood chips, or shredded leaves. This acts as a blanket, keeping the soil temperature stable. In areas with very wet winters, some gardeners also place a piece of plastic or a tarp over the mulched area to prevent the tubers from sitting in waterlogged soil, which can lead to rot.
Even in these warm zones, it is a good idea to dig and divide your dahlias every two or three years. Dahlia clumps grow larger each season, and they can eventually become overcrowded. Overcrowding leads to smaller flowers and poor air circulation, which can make the plants more susceptible to powdery mildew.
Mid-Winter Maintenance
Wintering dahlias isn't a "set it and forget it" task. To ensure the highest success rate, we suggest checking on your tubers about once a month. This allows you to catch any potential problems before they ruin the entire batch. For a broader overview of dahlia care, see All About Dahlias.
When you open your storage boxes, look for two main issues: rot and shriveling.
If you find a tuber that feels soft or mushy, or if you see fuzzy mold growing on it, remove it immediately. This prevents the rot from spreading to the healthy tubers nearby. If the mold is only on the surface and the tuber still feels firm, you can wipe it off with a cloth dipped in a very weak bleach solution and let it dry before putting it back.
If the tubers look wrinkled or feel light and "corky," they are drying out. You can fix this by lightly misting the storage material with a spray bottle of water. You don't want the material to be wet—just a tiny bit of moisture is usually enough to stop the shriveling.
Preparing for Spring Replanting
As the days get longer and the ground begins to thaw, your dahlia tubers will naturally start to wake up. You might notice the eyes on the crown becoming more prominent or even see small white sprouts beginning to form. This is an exciting sign that your wintering efforts have been successful!
You can start your dahlias indoors in pots about 4 to 6 weeks before your last frost date if you want an early start on blooms. Otherwise, simply wait until the soil has warmed to about 60°F and there is no longer a danger of frost. Most gardeners find that planting dahlias at the same time they plant their tomatoes is a safe rule of thumb. If you are ordering replacements or adding to your collection, check our Shipping Information page for timing by zone.
When you bring the tubers out of storage, give them one final inspection. Healthy tubers should feel firm, like a fresh potato. If some tubers didn't make it through the winter, don't be discouraged. Even professional growers expect a small percentage of loss. The tubers that did survive will often be larger and more vigorous than when you first bought them, giving you a head start on a beautiful summer display.
Troubleshooting Common Wintering Issues
Even with the best care, you might encounter a few challenges. The key is to respond quickly and keep things simple.
If you notice that your tubers are consistently rotting every year, the most likely culprit is too much moisture. Try using a drier storage medium next year, or increase the number of ventilation holes in your storage bins. It is also possible that the tubers weren't cured long enough before being packed away.
If your tubers are consistently shriveling, your storage area might be too warm or too dry. Moving the boxes to a cooler spot or using a more moisture-retentive packing material like peat moss can help. If you're looking for a lively next-season planting, browse Dahlia Dinnerplate High Summer Mix.
Sometimes, gardeners find that their tubers look perfectly healthy but never sprout in the spring. This usually happens if the "eye" was damaged or if the tuber was divided improperly and didn't include a piece of the crown. This is why many people prefer to wait until spring to divide, as the growth points are much more obvious.
Key Takeaway: Most dahlia storage problems are caused by an imbalance of moisture. Keep them cool, dark, and slightly "humid-dry" for the best results.
Conclusion
Wintering dahlia bulbs is a simple and satisfying way to extend the life of your garden and save money on new plants each year. By understanding the plant's need for a dormant period and providing a cool, stable environment, you can ensure your favorite varieties return bigger and better every summer. Whether you choose to store them in peat moss in your basement or mulch them heavily in the ground, the effort you put in now will be rewarded with a spectacular explosion of color next season.
We enjoy helping gardeners find success with these beautiful blooms. At Longfield Gardens, we take pride in providing 100% Quality Guarantee and the practical knowledge you need to keep them thriving for years to come. With your tubers tucked away safely for the winter, you can spend the cold months planning new color combinations with Dahlia Dinnerplate Summer Lovin Collection.
- Wait for the first frost to signal dormancy before digging.
- Cure tubers for 2–3 days in a cool, dry place to prevent rot.
- Store tubers in a breathable container with peat moss or vermiculite.
- Maintain a storage temperature between 40°F and 50°F.
The secret to successful dahlia wintering is maintaining a balance of moisture—keeping the tubers firm without letting them get wet.
Now that your dahlias are prepared for their winter rest, it’s the perfect time to start thinking about next year’s garden layout. Visit us at Longfield Gardens to discover Shop our New Dahlias Tubers for next season.
FAQ
Can I leave my dahlias in the ground if I live in a cold climate?
In areas where the ground freezes solid (generally USDA zones 7 and below), dahlia tubers will usually turn to mush and die if left in the ground. The water inside the tuber freezes and destroys the plant's cell structure. In these regions, lifting and storing them indoors is necessary for the plants to survive.
Do I need to wash the dirt off the tubers before storing them?
While it isn't strictly necessary to wash them perfectly clean, removing the bulk of the soil is highly recommended. Soil can harbor fungi and pests that may cause rot during the winter. If you have sandy soil, you can simply brush it off; for heavy clay, a gentle rinse with a hose is the best approach.
What should I do if my dahlia tubers have mold on them?
If you see a small amount of surface mold, don't worry. Wipe it off with a dry cloth or a very diluted bleach solution and ensure the tubers are dry before returning them to storage. However, if the tuber itself feels soft, squishy, or smells bad, it is rotting and should be thrown away immediately to protect the rest of the clump.
How do I know if a dahlia tuber is dead?
A dead tuber will usually be either very mushy and dark (rot) or very light, brittle, and shriveled like a dry twig (dehydration). A healthy, viable tuber should feel firm and heavy for its size, similar to a potato. If you are unsure, you can try planting it in the spring to see if it sprouts, as dahlias are often more resilient than they look.
