Introduction
There is nothing quite like the late-summer glory of a dahlia garden. From the massive, decorative dinnerplate varieties to the perfectly symmetrical pompons, these plants are the undisputed stars of the autumn landscape. As the season winds down, many gardeners feel a sense of accomplishment for the beautiful displays they have nurtured. At Longfield Gardens, we believe that the joy of growing dahlias shouldn't end when the first frost arrives. Saving your dahlia tubers is one of the most rewarding ways to expand your garden collection year after year without starting from scratch.
This guide is designed to help you navigate the simple process of lifting, cleaning, and storing your dahlia tubers so they remain healthy and ready for replanting next spring. Whether you are a beginner or a seasoned gardener looking to refine your technique, we will cover everything from identifying the right time to dig to choosing the best storage medium for your home environment. By following these practical steps, you can ensure that your favorite varieties return even stronger and more beautiful next season.
Saving your tubers is a straightforward process that relies on a few key principles of timing and care. With a little bit of preparation and the right storage conditions, you can turn a single season of color into a lifetime of blooms.
Understanding the Dahlia Life Cycle
Before you grab your pitchfork, it helps to understand what is happening beneath the soil. While we often call them "bulbs," dahlias actually grow from tubers—thick, fleshy roots that store energy for the plant. During the summer, the plant uses its foliage to produce energy through photosynthesis, which it then pumps down into these tubers to prepare for the following year.
In most parts of the United States (specifically Zones 2 through 7), dahlias cannot survive the freezing temperatures of winter in the ground. They are tropical plants by nature, originating from the warm mountain regions of Mexico and Central America. When the ground freezes, the water inside the tubers expands, causing the cell walls to burst and the tuber to turn into a mushy, non-viable mess. To prevent this, we lift them from the garden and provide a protected, dormant environment that mimics their natural rest period.
The goal of winter storage is to keep the tubers in a "Goldilocks" state: cool enough to stay dormant, but warm enough not to freeze; dry enough to prevent rot, but humid enough to prevent them from shriveling up.
When to Dig Your Dahlia Tubers
Timing is everything when it comes to lifting dahlias. If you dig them too early, the tubers may not have stored enough energy or developed a thick enough "skin" to survive the winter. If you wait too long, you risk a deep freeze that could damage the crown of the plant.
The First Frost Signal
For most gardeners, the most reliable signal to start digging is the first killing frost. This is the frost that turns the lush green foliage into a dark brown or black color. While it might look a bit sad to see your beautiful plants wilt, this is actually a helpful part of the process.
When the top growth dies back, the plant sends one final surge of energy down into the tubers. Many experts recommend waiting about 5 to 14 days after this first frost before you actually dig. This short waiting period allows the tubers to "cure" slightly in the ground and encourages the development of "eyes"—the small bumps where next year’s sprouts will emerge.
The 120-Day Rule
If you live in an area that doesn't get a frost until very late in the year, or if you need to clear your garden beds early, you can follow the 120-day rule. Generally, a dahlia tuber needs about four to five months of growth to be mature enough for successful storage. If your dahlias were planted in May, they are usually ready to be lifted by October, even if a frost hasn't hit yet.
Weather Considerations
Try to choose a dry, sunny day for digging. Working in soggy soil makes it harder to clean the tubers and increases the risk of mechanical damage (snapping a tuber off the clump) because the mud is heavy. If the forecast calls for a week of heavy rain followed by a hard freeze, it is better to dig a little early while the soil is manageable.
Key Takeaway: The ideal time to dig is about a week after the first killing frost has blackened the foliage, as this allows the tubers to mature and develop eyes for next season.
Step-by-Step Guide to Digging Dahlias
Once the timing is right, it’s time to head out to the garden. You want to be gentle during this process, as the "necks" of the tubers—the narrow part where they connect to the main stem—are quite fragile.
1. Cut Back the Stalks
Start by cutting the main stems down to about 4 to 6 inches above the ground. You can use sharp bypass pruners or loppers for thicker stems. This remaining piece of stem acts as a "handle" during the digging process and helps you keep track of where the center of the clump is located.
2. Loosen the Soil
Using a sturdy garden fork (a pitchfork) is generally better than a shovel. A shovel can easily slice through the tubers, while the tines of a fork are more likely to slide around them.
Insert the fork into the soil about 10 to 12 inches away from the main stem. You want to give the clump plenty of room, as dahlia tubers can spread out significantly during the growing season. Gently pry up on all sides of the plant to loosen the root system.
3. Lift the Clump
Once the soil is loose all the way around, place the fork deep under the clump and lift upward while gently holding the stem handle. If you feel resistance, stop and loosen the soil a bit more. Avoid yanking on the stem, as this can snap the necks of the dahlia clumps. A broken neck usually means the tuber won't be able to sprout next year, even if the tuber itself looks healthy.
4. Label Immediately
As soon as the clump is out of the ground, attach a label. It is incredibly easy to forget which variety is which once the flowers are gone. You can use a waterproof tag tied to the stem handle or write the name directly on a large tuber with a permanent marker later, but a temporary tag is essential the moment they leave the soil.
What to do next:
- Cut stems to 6 inches.
- Dig a wide circle (12 inches out) with a pitchfork.
- Gently lift the clump from underneath.
- Tag the variety immediately.
Cleaning and Prepping the Tubers
After digging, your tubers will likely be covered in garden soil. How you handle this depends on your soil type and your preference for fall or spring dividing.
Washing vs. Brushing
If you have heavy clay soil, it is often best to wash the tuber clumps with a gentle stream from a garden hose. Removing the mud allows you to see the structure of the clump, check for damage, and identify the "eyes."
If you have light, sandy soil, you might find it easier to let the clumps dry for a few hours and then simply brush the loose soil off with your hands or a soft brush. At Longfield Gardens, we have found that either method works, provided the tubers are handled with care.
The Drying (Curing) Period
Regardless of whether you wash them, the tubers need to dry before they go into storage. Place them in a frost-free, shaded area with good air circulation—such as a garage, shed, or covered porch. Lay them out on a piece of cardboard or a mesh screen.
Avoid placing them in direct sunlight, which can cause them to shrivel, and never let them sit directly on cold concrete, as it can pull moisture out of the tubers too quickly. Let them dry for 1 to 3 days until the outer skin feels firm and any remaining soil is dry to the touch.
Trimming and Inspection
Once dry, trim off any tiny, hair-like feeder roots. These will only rot in storage. You should also inspect the clump for any "mother" tubers (the original tuber you planted in the spring) that may be starting to decay. These are often darker and feel softer than the new tubers produced during the summer. If they look like they are rotting, remove them now to prevent the rot from spreading to the healthy new growth.
To Divide or Not to Divide?
One of the most common questions gardeners ask is whether they should divide the dahlia clumps into individual tubers in the fall or wait until spring. There are benefits to both approaches.
Dividing in the Fall
Pros: The tubers are softer and easier to cut. You save a significant amount of storage space because you aren't storing large clumps and excess soil. Cons: The "eyes" (the growth points) can be very difficult to see in the fall. If you cut a tuber and miss the eye, it will never grow.
Dividing in the Spring
Pros: After a winter of storage, the eyes will often begin to swell or even sprout, making them very easy to identify. You are less likely to end up with "blind" tubers. Cons: The clumps are much harder to cut through after they have cured for months. They also take up much more room in your storage bins.
Finding the Eye
To be viable, every individual tuber must have a piece of the "crown" (the area where the tuber meets the stem) that contains at least one eye. The eye looks like a tiny, raised bump or a small pimple. If you are a beginner, we recommend leaving your clumps whole or simply cutting them into two or three large sections. This ensures that each piece has plenty of eyes and enough stored energy to thrive.
Key Takeaway: If you are unsure where the eyes are, it is always safer to store the clump whole and divide it in the spring when the growth points become more obvious.
Successful Storage Methods
Once your tubers are clean, dry, and labeled, it’s time to tuck them away for the winter. The goal is to keep them dormant at a temperature between 40°F and 50°F.
The Storage Medium
You should never store dahlia tubers completely exposed to the air, as they will shrivel and die. Instead, pack them in a medium that helps regulate moisture. Popular choices include:
- Vermiculite: This is a favorite among many growers because it holds a small amount of moisture but allows for excellent aeration.
- Pine Wood Shavings: Often sold as animal bedding, these are inexpensive and effective at cushioning the tubers.
- Peat Moss: A classic choice, though it can sometimes be a bit too dry or too dusty.
- Newspaper: Wrapping individual tubers in several layers of newspaper can work well if your storage area has consistent humidity.
Packing the Bins
Use plastic storage bins, cardboard boxes, or even heavy-duty paper bags.
- Place a 2-inch layer of your chosen medium (like vermiculite or shavings) at the bottom of the container.
- Lay the tubers or clumps on top, making sure they aren't touching each other.
- Cover with another layer of medium.
- Repeat until the bin is full.
If you use plastic bins, do not snap the lid shut completely. Leave it slightly askew or drill a few small holes in the sides to allow for minimal air exchange. If the bin is airtight, moisture will build up and cause the tubers to rot.
Choosing the Right Location
Your storage spot is the most important factor in your success. An unheated basement, a crawl space, or a cool closet in a mudroom are often ideal. Some gardeners use an attached garage, but you must be certain the temperature will not drop below freezing. A single night of 30°F temperatures inside the garage can ruin your entire collection.
Monitoring Your Tubers Over Winter
Storing dahlias is not a "set it and forget it" task. You should check on your tubers about once a month throughout the winter. This allows you to catch small issues before they become disasters.
Checking for Rot
If you find a tuber that feels mushy or smells foul, remove it immediately. Rot can spread quickly through a storage bin. If only a small part of a tuber is affected, you can sometimes cut the bad part off with a sterile knife and let the cut end air-dry before putting it back.
Checking for Shriveling
If the tubers look wrinkled or feel light and "corky," they are losing too much moisture. To fix this, lightly mist the storage medium with a spray bottle of water. You don't want it to be wet—just slightly damp to the touch. This small boost in humidity is usually enough to stop the shriveling.
Handling Early Sprouts
As spring approaches, you might notice some tubers starting to sprout in their bins. This is normal and usually means your storage area is warming up. If it is still too early to plant outside, try to move them to a slightly cooler spot to slow them down, or simply leave them be until planting time.
Winter Care Summary:
- Check monthly for soft spots or mold.
- Remove any rotting tubers immediately.
- Mist the medium if tubers appear shriveled.
- Keep temperatures between 40°F and 50°F.
Common Myths About Storing Dahlias
There are many "internet hacks" for storing dahlias, but sticking to the basics is usually the most reliable path.
Myth 1: You must wash them with bleach. While some growers use a very diluted bleach dip to kill fungus, it isn't strictly necessary for the home gardener. Simply removing the soil and ensuring the tubers are dry is often enough to prevent disease.
Myth 2: You can store them in the refrigerator. While the temperature might be right, most refrigerators are "frost-free," meaning they are designed to remove humidity. This will shrivel your tubers very quickly. Additionally, ripening fruits and vegetables in the fridge release ethylene gas, which can damage the dormant tubers.
Myth 3: They are "deer-proof" in storage. Mice and voles actually find dahlia tubers quite tasty. If you store your bins in a garage or shed, make sure they are secure from rodents. Using plastic bins with ventilated lids is a good way to keep pests out while still allowing the tubers to breathe.
Preparing for Spring Replanting
As the ground begins to warm in the spring, your stored tubers will be ready to start their new journey. Before planting, give them one final inspection. Healthy tubers should feel firm, like a fresh potato.
If you stored your dahlias in whole clumps, this is the time to divide them. Look for those swelling eyes and use a sharp, sterilized knife to cut the clump into individual pieces. Remember to ensure each piece has a bit of the crown and an eye.
Don't be discouraged if a few tubers didn't make it through the winter. Even professional growers expect a small percentage of loss. The tubers that did survive will likely be larger and more productive than the year before, giving you even more blooms to enjoy.
Key Takeaway: Spring is the ideal time for final division, as the eyes are clearly visible and the tubers are ready to be woken up by the warmth of the new season.
Conclusion
Digging and storing dahlia bulbs is a cycle of renewal that connects one gardening season to the next. While it requires a bit of effort in the autumn, the reward of seeing those familiar favorites emerge from the soil in the spring is well worth the time. By focusing on the basics—proper timing, careful handling, and a cool, humid storage environment—you can successfully preserve your dahlia collection for years to come.
At Longfield Gardens, we want every gardener to feel confident in their ability to grow and maintain these stunning flowers. Remember that gardening is a learning process, and each year you store your tubers, you will gain a better understanding of what works best for your specific climate and home.
- Wait for the first frost to signal the start of the digging season.
- Handle tubers gently to protect the fragile necks and eyes.
- Store in a cool, dark place with a medium like vermiculite or wood shavings.
- Monitor monthly for moisture levels and signs of rot.
With these simple steps, you are well on your way to another spectacular season of dahlia blooms. Happy gardening!
FAQ
How long can dahlia tubers stay in the ground after a frost?
It is generally safe to leave them in the ground for 1 to 2 weeks after the first killing frost. This waiting period helps the tubers mature and makes the "eyes" easier to see. However, you must dig them before the ground freezes solid, as a deep freeze will kill the tubers.
Do I have to wash the dirt off the tubers before storing them?
Washing is not strictly required, but it is highly recommended if you have heavy or wet soil. Cleaning the tubers allows you to inspect them for rot, pests, and damage. If you choose not to wash them, make sure the soil is completely dry before placing them in storage containers.
What should I do if my stored tubers start to grow mold?
If you see a light dusting of white mold, it usually means your storage medium is too damp or there is not enough airflow. Wipe the mold off with a dry cloth, remove any mushy spots, and leave the tubers out in a dry area for a day before repacking them in fresh, drier material.
Can I store dahlias in a crawl space?
Yes, a crawl space can be an excellent storage location as long as it stays between 40°F and 50°F and remains dry. Ensure the tubers are protected from rodents and that the area does not experience extreme temperature fluctuations that could lead to freezing or premature sprouting.
