Table of Contents
- Introduction
- Understanding Dahlia Dormancy
- The Importance of Timing: When to Dig
- Preparing the Plants for Harvest
- How to Dig Without Damage
- Cleaning and Curing Your Tubers
- To Divide or Not to Divide?
- Choosing Your Storage Medium
- Selecting a Storage Location
- Monitoring Your Tubers Through Winter
- Preparing for Spring Planting
- Success with Every Variety
- Conclusion
- FAQ
Introduction
There is nothing quite like the late-summer magic of a dahlia garden in full bloom. From the massive, pillowy petals of dinnerplate dahlias to the intricate, honeycomb structures of pompons, these plants are the undisputed stars of the sunny border. Because we want to enjoy these spectacular flowers year after year, learning the simple process of winter storage is one of the most rewarding skills a gardener can master.
At Longfield Gardens, we believe that gardening should be a joyful, straightforward experience. While dahlias are technically tender perennials that cannot survive freezing ground temperatures, saving them for next season is surprisingly easy. If you prefer compact blooms, PomPon Dahlia is a great style to explore. By following a few basic steps, you can turn one season of beauty into a lifetime of blooms.
This guide will walk you through everything you need to know about harvesting, cleaning, and storing your dahlia tubers — often called bulbs — so they stay healthy and firm until spring. Whether you are a beginner or an experienced grower, these tips will help you protect your investment and expand your garden for free. Protecting your dahlias over the winter ensures a head start on next year's colorful display.
Understanding Dahlia Dormancy
Before we get into the "how," it helps to understand why we store dahlias. Most gardeners refer to the underground part of a dahlia as a "bulb," but they are actually tubers. Unlike a true bulb (like a tulip), which contains a miniature flower inside, a dahlia tuber is a nutrient-dense storage organ that provides the energy needed for the plant to sprout and grow each spring.
Dahlias are native to the high-altitude regions of Mexico and Central America. In their natural habitat, they experience a dry season rather than a freezing winter. This means they are biologically programmed to rest during the months when water is scarce or temperatures drop. In most of the United States (specifically USDA zones 2 through 7), the ground freezes deep enough to damage these water-rich tubers. If you're not sure of your zone, use our USDA Hardiness Zone Map.
Storing them indoors mimics their natural dry-season dormancy. It keeps the tubers safe from the rot that occurs in cold, wet soil and the cell damage caused by hard freezes. When you provide a cool, dark, and dry environment, the dahlia simply "sleeps" until the warmth of spring signals that it is time to grow again.
The Importance of Timing: When to Dig
The most common question we hear is exactly when to pull dahlias out of the ground. The answer is written in the weather. You want to leave the tubers in the soil as long as possible because the final weeks of the growing season are when the tubers do most of their "bulking up." This is when they store the starches and sugars they will need to survive the winter.
Wait for the first frost to hit your garden. You will know it has happened when the lush green foliage of your dahlias turns black or dark brown overnight. This might look a bit sad, but it is actually a positive signal. The frost tells the plant to shut down its top growth and send all remaining energy down into the tubers.
If you live in a region where a hard frost doesn't come until very late, you can usually aim to dig them up by mid-November. For more timing details, see When and How to Dig Up Dahlia Bulbs. However, for most gardeners, waiting about one to two weeks after the first killing frost is ideal. This short waiting period allows the "eyes" (the small bumps where next year’s stems will grow) to become more prominent, making them easier to see if you choose to divide your tubers.
Key Takeaway: The first frost is your friend. It signals the plant to enter dormancy, ensuring the tubers have the maximum amount of energy stored for their winter nap.
Preparing the Plants for Harvest
Once the foliage has blackened, the work begins. The first step isn't digging; it's cutting. Using a clean pair of bypass pruners or a sharp garden knife, cut the main stalks down so that only about 4 to 6 inches of the stem remains above the soil line.
Cutting the stalks first makes the digging process much easier to manage. It also allows you to see exactly where the center of the plant is so you don't accidentally spear the tubers with your tools. At this stage, it is vital to keep your labels organized. Since all dahlia tubers look similar once they are out of the ground, attach a waterproof tag or write the variety name directly on the remaining stem with a permanent marker.
Why Clean Tools Matter
Whenever you move from one plant to another, it is a good practice to wipe your blades with a disinfectant, such as a quick dip in a 10% bleach-to-water solution or a rub with isopropyl alcohol. This prevents the accidental spread of soil-born viruses or bacteria between your different varieties. It is a simple step that keeps your entire collection healthy.
How to Dig Without Damage
Dahlia tubers grow in a clump that looks a bit like a cluster of sweet potatoes. These tubers are attached to the main stem by a narrow "neck." This neck is quite fragile, especially right after digging when the plant is still full of moisture. If the neck breaks, the tuber may not be able to sprout next year, even if the body of the tuber is healthy.
To dig safely, follow these steps:
- Give them space: Start your digging about 12 inches away from the main stem. This ensures you aren't hitting the tubers, which can spread out quite a bit in healthy soil.
- Use a garden fork: A garden fork is generally better than a shovel because it is less likely to slice through a tuber. It allows the soil to fall through the tines as you lift.
- Loosen the soil: Gently push the fork into the ground on all four sides of the plant. Gently pry upward to loosen the root ball.
- Lift with care: Once the soil is loose, reach down and lift the entire clump from underneath while gently holding the stem for balance. Avoid pulling hard on the stem, as this is the easiest way to snap those fragile necks.
Cleaning and Curing Your Tubers
After the clumps are out of the ground, you will have a fair amount of garden soil clinging to them. For a deeper look at tuber anatomy, read Dahlia Tubers: What You Need to Know. Some gardeners prefer to wash their tubers with a gentle stream from a garden hose, while others prefer to let the soil dry and then brush it off.
The Washing Method
Washing is helpful because it allows you to see the health of the tubers clearly. It makes it easier to spot "eyes" and identify any signs of rot or insect damage. If you choose to wash them, make sure you do it gently. Once they are clean, turn the clumps upside down (stems pointing toward the ground) to allow any water trapped in the hollow stalks to drain out. This prevents "crown rot," which is one of the most common issues during storage.
The Curing Process
Curing is just a fancy word for letting the tubers dry out slightly before they go into a box. Place your clean, drained tubers in a frost-free, shaded area with good air circulation—like a garage or a covered porch—for 1 to 3 days. You don't want them to stay out so long that they shrivel, but you want the outer skin to feel dry and "cured." This toughens the skin and makes them more resistant to mold.
To Divide or Not to Divide?
One of the most intimidating parts of learning how to store dahlia bulbs over the winter is deciding whether to divide the clumps. Dividing is the process of cutting the large cluster into individual tubers. Each piece can then grow into a brand-new, full-sized plant next year.
You do not have to divide in the fall. Many gardeners prefer to store the entire clump and wait until spring to divide. In the spring, the "eyes" are much easier to see because they begin to swell and turn pink or green. However, dividing in the fall takes up much less storage space and the tubers are softer and easier to cut.
If you choose to divide now, remember the "Rule of Three." For a tuber to grow, it must have:
- The Body: The fat part of the tuber that holds the energy.
- The Neck: The narrow part that connects the body to the stem.
- The Eye: The small bump located on the "crown" (the area where the neck meets the old stem).
Without an eye, a tuber will never produce a sprout. If you aren't sure where the eyes are, it is always safer to leave the clump whole or just cut it into two or three large chunks.
Choosing Your Storage Medium
Dahlia tubers are like Goldilocks: they don't want to be too wet, or they will rot. They don't want to be too dry, or they will shrivel up and die. The goal of storage is to maintain a very slight amount of moisture while allowing for air circulation.
There are several popular materials you can use to pack your tubers:
- Peat Moss: This is a classic choice. It is naturally slightly acidic and holds moisture well without becoming soggy.
- Vermiculite: A mineral that provides excellent insulation and moisture regulation. It is very clean and easy to work with.
- Wood Shavings: The kind used for animal bedding works well. It provides great air circulation.
- Pine Bark: Often used in potting mixes, it is a good, coarse medium that prevents the tubers from touching one another.
- Newspaper: Some gardeners simply wrap individual tubers in several layers of newspaper.
At Longfield Gardens, we have found that a simple cardboard box or plastic bin lined with newspaper and filled with slightly damp peat moss or vermiculite is a very reliable method for most home gardeners.
Selecting a Storage Location
The environment where you keep your boxes is just as important as the packing material. The ideal temperature for storing dahlia tubers is between 40°F and 50°F.
- If it's too cold: If the temperature drops below freezing, the water inside the tubers will turn to ice, bursting the cell walls and turning the tuber into mush.
- If it's too warm: If the temperature stays above 55°F, the tubers may think it is spring and try to sprout prematurely, or they may simply dry out and shrivel.
Common successful storage spots include unheated basements, insulated garages, or cool crawlspaces. Avoid placing your boxes directly on concrete floors, which can pull moisture out of the containers or transfer cold too quickly. Instead, set them on a wooden pallet or a shelf.
What to Do Next: Your Storage Checklist
- Cut: Remove foliage after the first frost, leaving a 4-inch stem.
- Tag: Secure a label to the stem or write the name on the tuber.
- Dig: Lift carefully with a garden fork, starting 12 inches out.
- Dry: Cure in a cool, shaded spot for 1 to 3 days.
- Pack: Place in a box with peat moss or vermiculite, ensuring tubers don't touch.
Monitoring Your Tubers Through Winter
Storage isn't a "set it and forget it" task. To ensure the highest success rate, you should check on your dahlias about once a month. If you grow Single Dahlias, that monthly check is just as important for keeping the clumps in good shape.
When you open your boxes, look for two things:
- Signs of Rot: If you see a tuber that has become soft, mushy, or smells bad, remove it immediately. Rot can spread quickly through a box, so getting rid of the "bad apple" is essential.
- Signs of Shriveling: If the tubers look very wrinkled or feel light and hollow, they are getting too dry. You can lightly mist the packing medium with a spray bottle of water. Do not soak it; just add enough moisture to raise the humidity in the box.
If you notice a small amount of surface mold but the tuber is still firm, simply wipe it off and leave the box open for a day to improve air circulation. Often, a small adjustment in ventilation is all that is needed to keep things balanced.
Preparing for Spring Planting
As the days get longer and the threat of a hard freeze passes, you can begin to wake up your dahlias. In most regions, this happens in late April or May. When you pull them out of storage, you may already see small green or pink sprouts beginning to form at the eyes.
If you didn't divide your tubers in the fall, now is the perfect time. The eyes will be very obvious. You can also "presprout" your dahlias indoors about 4 to 6 weeks before your last frost date by placing them in pots with slightly damp soil. This gives them a head start and leads to earlier blooms in the summer.
Remember that dahlias love warm soil. Wait until the ground is at least 60°F before planting them outside. For more on planting temperature, see What Temperature Do Dahlias Need to Grow?. A simple rule of thumb: if the soil is warm enough to plant tomatoes, it is warm enough for your dahlias.
Success with Every Variety
Different varieties of dahlias may behave slightly differently in storage. Small, ball dahlias often produce very tough, resilient tubers that store easily. In contrast, some of the very large "dinnerplate" varieties may produce fewer, more sensitive tubers.
Growing dahlias is a journey that spans the entire year. If you want to compare more forms and colors, browse our Dahlia Collections. The satisfaction of pulling a firm, healthy tuber out of a box in April—knowing it will soon become a five-foot-tall plant covered in flowers—is one of the great rewards of the gardening life.
Conclusion
Storing dahlia bulbs over the winter is a straightforward process that pays off in abundance. If you want to add a spikier form to next year's garden, Dahlia Cactus My Love is a striking choice. By waiting for the first frost, digging with care, and providing a cool, stable environment, you can preserve your favorite flowers for years to come.
- Wait for the frost to ensure tubers are fully mature.
- Dry and cure the tubers for a few days to prevent rot.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly to adjust moisture levels and remove any damaged tubers.
At Longfield Gardens, we are dedicated to helping you find success in every season. Learn more on our About Us page, where we explain our 100% Quality Guarantee. With a little bit of preparation this fall, your garden will be ready to burst into a spectacular display of color when spring returns.
"The effort you put into protecting your dahlias today is the foundation for the breathtaking blooms you will enjoy tomorrow."
FAQ
Do I have to wash the dirt off dahlia tubers before storing them?
Washing is optional but highly recommended. Removing the soil helps you see the "eyes" for dividing and allows you to spot any hidden rot or pests. If you choose to wash them, ensure they are dried thoroughly for 24 to 48 hours before packing them away to prevent mold.
Can I store dahlias in a refrigerator?
It is possible to store dahlias in a refrigerator, but it is often risky. Most refrigerators are kept at about 35–38°F, which is very close to freezing, and the air is often very dry. If you use a fridge, keep the tubers in the crisper drawer in a sealed bag with plenty of peat moss to prevent them from drying out.
What happens if I don't dig up my dahlias?
In USDA zones 7 and colder, dahlia tubers left in the ground will almost certainly freeze and turn into mush over the winter. In warmer zones (8 and higher), you can sometimes leave them in the ground if the soil is well-draining, but it is still a good idea to cover the area with a thick layer of mulch to protect them from cold snaps.
Why did my dahlia tubers shrivel up during the winter?
Shriveling occurs when the storage environment is too dry or the temperature is too warm. If the tubers lose too much moisture, they won't have the energy to sprout in the spring. To prevent this, ensure they are packed in a medium like peat moss and check them monthly; if they look wrinkled, lightly mist the packing material with water. For more growing advice, see 8 Tips for Growing Better Dahlias.
