Introduction
There is a unique kind of magic in watching a dahlia bloom for the first time in summer. Whether it is the massive, intricate petals of a dinnerplate variety or the perfectly geometric shape of a pompon, these dahlias are the undisputed stars of the late-season garden. At Longfield Gardens, we believe the only thing better than enjoying a beautiful dahlia today is knowing you can enjoy that same plant again next year.
Saving your favorite varieties is a rewarding and cost-effective way to expand your garden. Because dahlias are native to the warm climates of Mexico and Central America, they cannot survive freezing temperatures in the ground in most parts of the United States. However, with a few simple steps, you can lift, store, and protect these treasures through the winter months. If you are planning your next big display, a dinnerplate dahlia collection is a great place to start.
This guide will walk you through the process of harvesting, cleaning, and storing your dahlia tubers so they stay healthy and ready for spring. You will learn the best timing for digging, how to identify the "eyes" for future growth, and which storage methods work best for your home. By the end, you will feel confident in your ability to keep your dahlia collection thriving year after year. If you love the tight, rounded form of a pompon, you can find that style here too.
Understanding the Dahlia Life Cycle
To save your dahlias successfully, it helps to understand what is happening beneath the soil. For a broader refresher on the full growing cycle, see All About Dahlias. While many gardeners refer to them as "bulbs," dahlias actually grow from tubers. A tuber is a thickened, underground stem that stores nutrients and energy for the plant.
Unlike a tulip bulb, which contains a miniature flower inside, a dahlia tuber is more like a battery. It provides the fuel needed to push up new green shoots when the soil warms in the spring. During the summer, the mother tuber you planted in the spring works hard to grow a beautiful plant. As the season progresses, that single tuber multiplies into a clump of several new tubers.
By saving this clump over the winter, you are not just saving one plant; you are often gaining several new ones. This natural multiplication is what makes dahlias such a wonderful investment for your landscape. As long as you provide a cool, dark, and dry place for them to rest, they will be ready to perform all over again once the danger of frost has passed.
Timing the Harvest: When to Dig
The most common question regarding how to save dahlia bulbs over winter is exactly when to take them out of the ground. Timing is everything, and the best signal comes directly from nature.
In most regions, you should wait until a frost has touched the plants. A light frost will turn the dahlia foliage black or brown, signaling to the plant that it is time to go dormant. This transition is important because it tells the plant to move all its remaining energy from the leaves and stems down into the tubers.
The Waiting Period
Many experienced gardeners prefer to wait about a week after the first killing frost before digging. This short waiting period allows the tubers to "cure" slightly while still in the ground, which can toughen their skins. Tougher skins are less likely to be nicked or bruised during the digging process and often hold up better in storage.
If you live in a region where a hard freeze (temperatures consistently below 28°F) is expected early, do not wait too long. While the foliage can handle a light frost, the tubers themselves can be damaged if the ground freezes several inches deep. Your goal is to lift them while the soil is still workable but the plant has stopped growing.
Labeling Your Varieties
Before the frost hits and turns your garden into a sea of brown stems, make sure your plants are clearly labeled. Once the flowers are gone, it is nearly impossible to tell a Café au Lait from a similar dinnerplate dahlia.
Use waterproof tags or surveyors' tape to tie labels directly to the base of the stems. This ensures that when you pull the tubers out of the ground, you know exactly what you are putting into storage, especially if you grow Thomas Edison.
Key Takeaway: Wait for the first frost to turn the foliage brown. This signals the plant to store its energy in the tubers for next year.
How to Dig Without Damage
Dahlia tubers are surprisingly brittle, especially where the tuber meets the central stem. This area, known as the "neck," is vital for the tuber's survival. If the neck is snapped or severely creased, the tuber may not be able to sprout in the spring.
Step-By-Step Digging
- Cut the Stems: Start by cutting the dahlia stems down to about 4 to 6 inches above the soil line. These short "handles" make it easier to see where the plant is and give you something to hold onto, but be careful not to pull on them too hard.
- Go Wide: Use a garden fork or a sturdy shovel. Position your tool at least 12 inches away from the base of the stem. Digging too close is the most common way to accidentally slice through a healthy tuber.
- Loosen the Soil: Gently push the fork into the soil and pry upward. Move in a circle around the plant, loosening the earth from all sides.
- Lift Carefully: Once the soil is loose, reach under the clump with your hands or the fork and lift the entire root ball out of the ground.
- Shake Off Excess: Gently shake the clump to remove large chunks of soil. Do not bang the tubers against each other or a hard surface, as this can cause bruising.
Cleaning and Curing Your Tubers
Once the tubers are out of the ground, they need a little preparation before they go into their winter home. There are two main schools of thought on cleaning: washing them with water or simply brushing off the dry dirt. Both methods can be successful, but your choice might depend on your storage environment. If you want a step-by-step refresher on the whole process, see our guide to How to Lift and Store Dahlia Bulbs.
The Washing Method
Washing your tubers with a gentle stream from a garden hose allows you to see the "eyes" and the general health of the clump more clearly. It also removes soil-borne pests or fungi. If you choose to wash them, it is critical that you let them dry completely before packing them away. Any lingering moisture trapped in the nooks and crannies of the clump can lead to rot during the winter.
The Dry-Brush Method
If your soil is sandy and falls away easily, you might prefer to let the clumps dry in a frost-free area for a day or two and then simply brush off the remaining dirt with your hands or a soft brush. This method is often easier for beginners because it reduces the risk of introducing excess moisture.
Curing for Storage
Regardless of how you clean them, all dahlia tubers benefit from a "curing" period. Place the tubers in a cool, dry area away from direct sunlight and wind for 24 to 48 hours. A garage or a covered porch works well, provided the temperatures stay above freezing. This drying time helps the outer skin dry out and the cut stems to callus over, creating a natural barrier against decay.
What to do next:
- Remove any remaining green leaves from the stalks.
- Inspect the tubers for holes or soft spots.
- If you find any rotten tubers, trim them away with a clean, sharp knife.
- Ensure the variety labels are still securely attached.
Dividing: Now or Later?
One of the most common debates among dahlia enthusiasts is whether to divide the tuber clumps in the fall or wait until the spring. At Longfield Gardens, we find that both methods have their benefits, and the "right" choice often depends on your schedule and storage space.
Dividing in the Fall
Dividing in the fall saves a significant amount of space. Instead of storing large, bulky clumps of soil and roots, you only store the individual, viable tubers. Fall dividing is also easier because the tubers are softer and easier to cut.
However, the "eyes" (the small bumps that will become next year’s stems) can be very difficult to see in the fall. If you divide in the autumn, you run the risk of cutting off a tuber that doesn't have an eye, which means it will never grow.
Dividing in the Spring
Waiting until spring is often the safer bet for beginners. As the weather warms and the tubers wake up, the eyes begin to swell and may even turn slightly pink or green. This makes it very easy to see exactly where to make your cuts. The downside is that the tubers become much tougher over the winter, requiring a bit more muscle and a very sharp set of bypass pruners to separate.
How to Identify a Viable Tuber
Whether you divide now or later, a dahlia tuber must have three parts to grow:
- The Body: The fat part that stores the food.
- The Neck: The thin part that connects the body to the stem.
- The Eye: Located on the "crown" (the area where the neck meets the old stem).
If a tuber breaks off without a piece of the crown and a visible eye, it is essentially useless for planting, though it can still be a fun experiment to see if a "blind" tuber surprises you.
Choosing Your Storage Medium
The goal of winter storage is to keep the tubers in a state of suspended animation. You want to prevent them from freezing, but you also want to keep them from drying out completely (shriveling) or staying too wet (rotting).
The "perfect" storage medium often depends on the humidity of your storage space. We recommend trying one of these common materials:
Vermiculite or Perlite
These lightweight mineral products are excellent for dahlia storage. They hold a tiny bit of moisture but allow for plenty of air circulation. Many gardeners find that tubers stored in vermiculite stay plump and healthy with very little maintenance.
Peat Moss or Coco Coir
Peat moss is a traditional choice because it is naturally slightly acidic, which can help inhibit mold. If you use peat moss, make sure it is just barely damp—if you squeeze a handful, no water should come out. If it is too dry, it can actually suck moisture out of your tubers.
Wood Shavings
Large flake wood shavings (the kind sold for animal bedding) are an affordable and effective option. They provide great insulation and air gaps, which prevent rot from spreading from one tuber to another. Avoid fine sawdust, which can pack too tightly and hold too much moisture.
The Plastic Wrap Method
A more modern approach involves wrapping individual, cleaned tubers tightly in plastic kitchen wrap. This creates a tiny micro-environment for each tuber, preventing moisture loss. While this takes more time upfront, it allows you to see each tuber throughout the winter and prevents a single rotten tuber from ruining the whole batch.
The Ideal Storage Environment
Where you put your dahlias is just as important as how you pack them. They need a "Goldilocks" environment: not too hot, not too cold, and not too dry.
Temperature
The ideal temperature for dahlia storage is between 40°F and 50°F. If the temperature drops below freezing, the water inside the tubers will expand and turn them to mush. If the temperature stays above 60°F, the tubers may think it is spring and try to sprout prematurely, or they may simply shrivel and die from the heat.
Unheated basements, crawl spaces, and insulated garages are usually the best spots. If you use a garage, keep the boxes off the concrete floor by placing them on a shelf or a wooden pallet, as the floor can get much colder than the air.
Containers
You can store your packed tubers in cardboard boxes, plastic bins, or even paper bags.
- Cardboard boxes allow for some "breathing," which is good if your storage area is a bit damp.
- Plastic bins are better if your storage area is very dry, as they help retain moisture. However, if you use plastic, do not snap the lid on tight; leave it cracked an inch or two to allow for gas exchange.
Key Takeaway: Success comes down to moisture management. You want your tubers to feel like a firm potato, not a soft sponge or a dried-out raisin.
Winter Maintenance: The Mid-Season Check
Saving dahlia tubers is not a "set it and forget it" task. To ensure the highest success rate, you should check on your tubers at least once a month.
When you open your storage containers, look for two things:
- Rot: If you see a tuber that has turned soft, black, or fuzzy with mold, remove it immediately. Rot can spread quickly through a box. If only a small part of a tuber is affected, you can sometimes cut the bad part off and let the healthy part dry before putting it back.
- Shriveling: If the tubers look wrinkled and feel light, they are losing too much moisture. You can fix this by lightly misting the storage medium with a spray bottle of water. Do not soak them; a very light mist is all they need to rehydrate.
Preparing for Spring
As the days get longer and the ground begins to thaw, your dahlias will naturally start to wake up. For a broader refresher on planting and seasonal care, see What Conditions Do Dahlias Need to Grow?. This is the time to bring your boxes out of the dark and into a slightly warmer area.
If you didn't divide your tubers in the fall, now is the time to do it. You will see those small, pimple-like eyes swelling near the stems. Use a sharp, clean knife to separate the clumps, ensuring each piece has at least one healthy eye.
Don't be discouraged if you lose a few tubers over the winter. Even professional growers expect a small percentage of loss due to natural variation or storage fluctuations. The tubers that do survive will be stronger and ready to provide a spectacular show in your garden.
Conclusion
Learning how to save dahlia bulbs over winter is one of the most practical skills a home gardener can develop. It turns a one-season display into a lifelong hobby and allows you to share your favorite varieties with friends and neighbors. By following the simple steps of waiting for the frost, digging carefully, and maintaining a cool, dark storage space, you can protect your garden investment and ensure a vibrant landscape for years to come.
- Wait for the frost to signal dormancy.
- Dig wide to avoid damaging the brittle tubers.
- Clean and cure the tubers to prevent rot.
- Store in a cool, dark place between 40°F and 50°F.
At Longfield Gardens, we want every gardener to experience the joy of a flourishing dahlia bed. For peace of mind, our 100% Quality Guarantee helps keep that promise. If you want another color-packed option for next season, browse the Dahlia Dinnerplate Summer Lovin Collection.
If you would like more timing details, review our Shipping Information before you place your order.
Your dahlias are hard at work even when they are resting. Give them the right winter home, and they will reward you with a magnificent performance next summer.
FAQ
Can I leave my dahlia tubers in the ground if I use extra mulch?
In USDA hardiness zones 8 and warmer, you can often leave dahlias in the ground if the soil is well-drained and you apply a thick layer of mulch. If you're not sure what zone you're in, check the USDA hardiness zone map. However, in zones 7 and colder, the ground usually freezes deep enough to kill the tubers, making it necessary to dig and store them indoors.
What should I do if my dahlia tubers get moldy in storage?
If you find mold, immediately remove the affected tubers and throw them away to prevent the mold from spreading. Check the moisture level of your storage medium; if it feels wet, replace it with fresh, dry material and increase the airflow in your storage area by leaving the lids off your containers.
Do I have to wash the dirt off the tubers before storing them?
No, washing is not strictly necessary. In fact, leaving a little bit of soil on the clumps can sometimes provide a natural protective barrier. The most important thing is that the tubers are dry when they go into storage, so if you do wash them, give them plenty of time to air dry first.
Why did my dahlia tubers shrivel up and become hard over the winter?
Shriveling happens when the storage environment is too dry or the storage medium (like peat moss) has sucked the moisture out of the tubers. To prevent this, check them monthly and use a spray bottle to lightly mist the packing material if the tubers start to look wrinkled.
