Introduction
There is nothing quite like the late-summer splendor of a dahlia in full bloom. These garden champions offer an incredible variety of colors and shapes, from dainty pompons to massive dinnerplate dahlias that can be larger than a salad plate. Because they bloom so vigorously right up until the first frost, they often become the highlight of the autumn garden. At Longfield Gardens, we believe every gardener should be able to enjoy these spectacular flowers year after year, especially through our dahlia collections.
Since dahlias are native to the warm climates of Mexico and Central America, they are not naturally equipped to survive freezing winter temperatures in most parts of the United States. While they are often called "bulbs," they are actually tubers—thick, fleshy roots that store energy for the following year. Learning how to properly lift and store these tubers is a simple skill that protects your investment and ensures your garden returns even more beautiful the next spring.
This guide will walk you through the entire process, from the first frost to the final storage spot. We will cover the best tools for the job, how to cure the tubers so they stay healthy, and the exact conditions they need to survive until planting time. By following these straightforward steps, you can keep your favorite varieties thriving for many seasons to come.
Waiting for the Right Time to Dig
Timing is everything when it comes to overwintering dahlias. The most common question gardeners ask is when exactly they should pull their plants out of the garden. The answer lies in the weather and the appearance of the foliage.
For the tubers to be successful the following year, they need as much time as possible to store energy. Throughout the summer and early fall, the green leaves are busy turning sunlight into starches. These starches are tucked away in the tubers, providing the "fuel" the plant needs to sprout again in the spring. If you dig them up too early, the tubers may be small or lack the energy to grow strong stems later.
In most regions, the signal to start is the first "killing frost." This happens when temperatures drop low enough to turn the lush green leaves into a dark, wilted brown or black. While the top of the plant looks finished, the tubers underground are perfectly safe. In fact, many experienced gardeners like to wait about a week or two after this first frost before they start digging. This short waiting period, often called "curing in the ground," helps the tubers toughen their skins and prepares them for dormancy.
If you live in a climate where a hard frost doesn't occur until very late in the year, aim to lift your tubers by mid-November. As long as the plants have had at least 120 to 150 days of growth, the tubers will be mature enough for storage.
Preparing the Plants for Lifting
Once the foliage has been hit by frost and turned brown, the first step is to clear away the top growth. You do not want to try digging up the entire plant with all its heavy stems and leaves still attached.
Use a pair of clean, sharp loppers or hand pruners to cut the main stems down. A good rule of thumb is to leave a "handle" of about 4 to 6 inches of stem protruding from the ground. This handle is very useful for lifting the clump out of the soil and serves as a place to attach a waterproof label so you don’t forget which variety is which.
Dahlia stems are hollow, which can sometimes allow water to collect inside the "handle." If heavy rain is expected between the time you cut the stems and the time you dig them up, you can loosely cover the cut ends with a piece of aluminum foil or turn a small pot upside down over them. This simple step keeps the center of the tuber clump dry and reduces the risk of rot.
What to do next:
- Check your local weather forecast for the first expected frost.
- Locate your garden labels or prepare new ones so you can identify your dahlias once they are out of the ground.
- Ensure your pruners and garden fork are clean and ready for use.
How to Dig Dahlia Tubers Safely
Digging up dahlias requires a bit of finesse. The tubers are quite fragile and can snap off the main stem easily. For a closer look at how dahlia tubers grow and are sold, see our guide. If a tuber breaks off and loses its "neck"—the thin part that connects it to the main stalk—it will likely not grow next year because the growth buds, or "eyes," are located right at that junction.
The best tool for this job is a sturdy garden fork rather than a shovel. A shovel has a solid blade that can easily slice through a hidden tuber, whereas the tines of a fork are more likely to slide around them.
Start by placing your fork about 12 inches away from the base of the stem. You want to give the clump plenty of room. Gently push the fork into the soil and lean back on the handle to loosen the earth. Move around the plant in a circle, loosening the soil from all sides. Once the ground feels soft and the clump begins to move, use the fork to pry the tubers upward while gently holding the stem handle with your other hand.
Lift the entire clump out of the ground and gently shake it to remove large clods of dirt. If your soil is very heavy or wet, don’t try to force all the dirt off immediately, as the weight of the mud can cause the tubers to snap.
Cleaning and Inspecting the Tubers
After the clumps are out of the ground, they need a bit of cleaning. There are two schools of thought on this: the "wash" method and the "brush" method.
If you have sandy soil that falls away easily, you can simply let the clumps sit in a dry, shaded area for a few hours and then brush off the remaining dirt with your hands or a soft brush. However, if you have heavy clay soil, it is often better to use a garden hose with a gentle spray setting to wash the dirt away. This allows you to see the health of the tubers clearly.
While cleaning, keep an eye out for any signs of damage or disease. Look for:
- Rot: Soft, mushy spots that may smell unpleasant.
- Damage: Deep cuts from the digging fork.
- Pests: Any signs of insects burrowing into the tubers.
Use a clean, sharp knife to trim away any mother tubers that look shriveled or exhausted. These are the original tubers you planted in the spring; they often look darker and more wrinkled than the new, plump tubers that grew over the summer. You should also trim off any "rat tails," which are long, thin roots that don't have a storage body. These won't help the plant next year and can often be the first parts to rot in storage.
The Importance of Curing
Curing is perhaps the most overlooked step in storing dahlias, but it is vital for long-term success. Curing is simply the process of letting the tubers dry out slightly so their outer skin toughens up. This skin acts as a protective barrier against rot and prevents the inner moisture from evaporating too quickly.
Find a spot that is cool, dry, and out of direct sunlight. A garage, a shed, or a basement works well. Do not leave the tubers outside if there is a risk of another frost, as a freeze will kill them instantly. Lay the clumps out on a piece of cardboard, a wooden pallet, or a mesh screen. It is best to turn them upside down so that any water trapped in the hollow stems can drain out.
Let the tubers sit for 3 to 7 days. By the end of this period, the skin should feel a bit more like a potato skin—firm and dry to the touch. The cut ends of the stems should also look dry and "calloused" over.
To Divide or Not to Divide
Once the tubers are clean and cured, you have a choice: you can store the entire clump as it is, or you can divide it into individual tubers now.
Storing Whole Clumps
Storing the whole clump is the easiest method for beginners. It takes up more space, but it also protects the "eyes" of the dahlia throughout the winter. Because the tubers remain attached to the main stalk, they are less likely to dry out completely. If you have plenty of storage space, this is often the safest bet.
Dividing in the Fall
Some gardeners prefer to divide their tubers in the fall because the "eyes" (the small bumps where new growth starts) are sometimes easier to see right after digging. Dividing also allows you to fit more tubers into a smaller storage container.
If you choose to divide now, ensure each piece has three things: a piece of the old stem (the "crown"), a healthy neck, and a plump tuber body. If any of these three parts are missing, the tuber will not grow. Use a sharp, sterilized knife and dip it in a mild bleach solution or rubbing alcohol between different plants to prevent the spread of any potential viruses.
Key Takeaway: Whether you divide now or in the spring, the goal is to keep the tubers firm and the "eyes" protected. If you aren't sure where the eyes are, it is perfectly fine to wait until spring when they begin to swell and turn pink or white.
Choosing the Best Storage Medium
Dahlia tubers are like the "Goldilocks" of the garden world—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 up and die. The storage medium you choose helps regulate this moisture level.
There are several effective materials you can use to pack your tubers:
- Vermiculite: This is a mineral that holds a small amount of moisture but allows for excellent air circulation. It is many gardeners' top choice.
- Peat Moss: This is very common and effective. It should be used slightly damp—not wet. If you squeeze a handful, it should feel moist but no water should drip out.
- Pine or Cedar Shavings: The kind used for animal bedding. These are very dry, so you may need to check your tubers more often to ensure they aren't shriveling.
- Perlite: Similar to vermiculite, but it holds less moisture. It is a good option if your storage area is naturally humid.
At our facility at Longfield Gardens, we see the best results when tubers are packed loosely so they aren't crushed, but are surrounded by enough material to prevent them from touching one another. If one tuber happens to rot, the storage medium acts as a buffer so the rot doesn't spread to the whole batch.
Packing Your Tubers for the Winter
Once you have your medium ready, it's time to pack. You can use cardboard boxes, plastic bins, or even heavy-duty paper bags.
If you use plastic bins, do not snap the lid on tight. You need a little bit of air exchange so moisture doesn't build up and cause mold. You can leave the lid slightly ajar or drill a few small holes in the sides of the bin. Cardboard boxes are naturally "breathable," which is great for preventing rot, but they may allow the tubers to dry out faster if your storage area is very dry.
Step-by-Step Packing:
- Place a 2-inch layer of your chosen medium (like vermiculite or peat moss) at the bottom of the container.
- Lay the tubers or clumps on top of the layer. Make sure they aren't crowded.
- Cover the tubers with more medium until they are completely buried.
- If you have a deep container, you can add a second layer of tubers, but try to keep it to no more than two or three layers.
- Place your label inside the box or tape it to the outside so you know exactly what is in there.
Finding the Perfect Storage Location
The environment where you keep your packed tubers is the final piece of the puzzle. The goal is a consistent temperature between 40°F and 50°F.
If the temperature drops below 32°F, the water inside the tubers will freeze, causing the cells to burst. When they thaw, they will turn into a mushy, black mess that cannot be saved. On the other hand, if the temperature stays above 55°F, the tubers may think it’s time to grow and start sprouting prematurely, or they may simply dry out and shrivel.
Common Storage Spots:
- Unheated Basements: Usually the most reliable spot in older homes.
- Attached Garages: Can work well, but be careful of "hot spots" near the house wall or "cold spots" near the garage door.
- Root Cellars: The traditional choice, offering great humidity and cool temps.
- Crawl Spaces: Often have the perfect temperature, but can sometimes be too damp.
Avoid placing your storage containers directly on a concrete floor. Concrete can pull moisture out of the containers or, conversely, can be very cold. Placing your boxes on a wooden pallet, a shelf, or even a piece of thick cardboard will help insulate them.
Monthly Maintenance and Troubleshooting
Storing dahlias isn't a "set it and forget it" task. To ensure the highest survival rate, you should check on your tubers about once a month throughout the winter. This allows you to catch small issues before they become big problems.
What to Look For:
When you open your storage bins, look for two main things: shriveling and rot.
If the tubers look shriveled: This means the air is too dry or your storage medium has lost its moisture. The tubers might look like a wrinkled raisin. To fix this, use a spray bottle to lightly mist the storage medium with water. Do not soak it—just add enough moisture to raise the humidity. You can also try closing the lid of your bin a bit tighter to hold in what moisture remains.
If the tubers look fuzzy or mushy: This is a sign of mold or rot caused by too much moisture or poor air circulation. If you find a soft tuber, remove it immediately and throw it away. If only a small part of a clump is rotting, you can try cutting the bad part off with a clean knife and letting the cut end dry out before putting it back. To prevent further issues, leave the lid off the container for a few days to let it dry out, or add some fresh, dry storage medium.
Key Takeaway: A quick five-minute check once a month is the best way to ensure you have healthy plants ready to go in the spring. Most losses happen because a single rotten tuber is left to infect the rest of the box.
Summary of the Overwintering Process
The process of storing dahlia tubers can be broken down into a few simple stages. By following this path, you take the guesswork out of winter care.
- Wait for Frost: Let the foliage turn brown to ensure the tubers are mature.
- Cut and Dig: Leave a handle, use a fork, and be gentle with the "necks."
- Clean and Cure: Remove soil and let the skins toughen for a few days in a cool, dry spot.
- Pack Correctly: Use a breathable medium like vermiculite or peat moss in a container that allows some airflow.
- Monitor Temps: Aim for 40–50°F and avoid freezing conditions.
- Check Monthly: Address shriveling or rot early to save the majority of your collection.
Conclusion
Successfully storing dahlia tubers is one of the most rewarding skills a gardener can learn. It allows you to build a collection of your favorite varieties and even share extra tubers with friends and neighbors as your clumps grow larger each year. While it may seem like a lot of steps, each part of the process is simple and easy to master with a little practice. We are always here to help you grow a more beautiful garden, and we stand behind the quality of the plants we provide.
Storing your dahlias is not just about saving money; it’s about preserving the life and history of your garden. Each tuber you save is a head start on next year’s beauty.
- Wait for the first frost to signal the start of the digging season.
- Always use a garden fork to prevent accidental damage to the new dahlia tubers.
- Ensure the storage area stays cool but never reaches the freezing point.
- Check your dahlia tubers once a month to manage moisture levels.
We hope this guide gives you the confidence to lift and store your dahlias this season. For more help with your garden, you can explore our All About Dahlias guide or reach out to us at Longfield Gardens for expert advice on all things bulbs and perennials.
FAQ
Can I leave my dahlia tubers in the ground over winter?
This depends entirely on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlias in the ground if you provide a thick layer of mulch (about 6 inches) to protect them from occasional dips in temperature. However, in Zone 7 and colder, the ground will freeze deep enough to kill the tubers, so digging them up is necessary for survival.
Should I wash the dirt off my tubers before storing them?
Washing is a matter of preference and soil type. If you have heavy clay soil, washing with a hose helps you see any rot or damage and makes dividing easier. If you have light, sandy soil, you can often just brush the dirt off. The most important thing is that if you do wash them, you must allow them to dry completely during the curing stage before packing them away.
What happens if my dahlia tubers shrivel during the winter?
Shriveling is a sign that the dahlia tubers are losing moisture to the air. If you catch it early, you can save them by lightly misting the packing material with water or adding a bit of damp vermiculite to the box. As long as the tuber is still somewhat firm and not completely dried out like a stick, it will usually recover and grow once planted in the spring. If you are unsure whether the clump is still viable, contact us for help.
Do I have to wait for a frost to dig up my dahlias?
While a frost is the most common signal, you don't strictly have to wait for it. If you live in an area with very late frosts or if you need to clear your garden beds early, you can cut the dahlias back manually in mid-autumn. The key is to ensure the plants have had at least four months of growth so the tubers are large enough to contain the energy needed for dormancy.
