Introduction
The end of the gardening season doesn't have to mean saying goodbye to your favorite flowers. If you have spent the summer admiring the massive blooms of dinnerplate dahlias or the intricate petals of pompon varieties, you already know why these plants are so beloved. While dahlias are tropical plants that cannot survive freezing temperatures in most parts of the country, they have a wonderful built-in survival tool: their tubers. These starchy, potato-like roots store all the energy the plant needs to grow again next year.
At Longfield Gardens, we want to help you enjoy your garden year after year without starting from scratch every spring. Learning how to store dahlia tubers during the winter is a simple skill that allows you to build a permanent collection of your favorite colors and shapes. This guide is designed for home gardeners who want a practical, step-by-step method to protect their investment and ensure a beautiful display next summer.
Storing your tubers is a rewarding way to extend the life of your garden and see your plants grow larger and more productive each season. If you'd like help comparing varieties and planning what to grow next, see our Planning Guide for Dahlias. By following a few basic steps to dig, clean, and pack your tubers, you can successfully overwinter them regardless of how cold your local climate gets. Storing dahlia tubers is a straightforward process that rewards a little bit of autumn effort with a spectacular summer payoff.
Why Dahlias Need Winter Protection
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 one. Because they are not adapted to frozen soil, the water inside the tubers will expand and burst the cell walls if the ground freezes. This turns the once-firm tuber into a mushy, unusable mess.
In most of the United States, specifically USDA hardiness zones 7 and colder, dahlias must be lifted from the ground and kept in a frost-free environment. Even in warmer zones where the ground doesn't freeze deep enough to kill the tubers, many gardeners still choose to dig them up. This is because dahlias can rot in cold, wet winter soil. Digging them up allows you to inspect the health of the plant, divide the clumps to create even more flowers, and ensure they stay in peak condition for the next growing season.
Timing the Harvest
The most important rule of dahlia storage is to let nature tell you when it's time. You should not dig up your tubers while the plant is still actively growing and green. As the days shorten and the temperatures drop, the dahlia plant begins to move its energy and nutrients from the leaves and stems down into the tubers. This process "cures" the tubers and prepares them for dormancy.
Wait for the first frost of the season. A light frost will usually turn the foliage black or brown. This might look a bit sad at first, but it is actually a vital signal to the plant to stop growing and start resting. Once the foliage has turned dark, we recommend waiting about 5 to 7 days before digging. This short waiting period allows the tubers to fully absorb the remaining energy from the plant and toughen their "skins," which makes them more resistant to rot and shriveling during storage.
Key Takeaway: Always wait for a killing frost to blacken the foliage before digging. This ensures the tubers are mature, dormant, and ready for their winter rest.
What to do next:
- Monitor your local weather forecast for the first "killing frost."
- Once the frost hits, cut a few labels or use a permanent marker to ensure you know which plant is which.
- Gather your tools, including a garden fork and bypass pruners.
Cutting Back the Foliage
Once your plants have been hit by frost and have rested for a few days, it is time to clear the way for digging. Use a sharp pair of pruners or a garden lopper to cut the main stalks down. Leave about 4 to 6 inches of the stem protruding from the ground.
These short "handles" serve two purposes. First, they help you locate the center of the tuber clump so you don't accidentally stab the roots with your shovel. Second, they provide a convenient place to attach a label. Dahlias look remarkably similar once they are out of the ground, and it is very easy to mix up a Café au Lait if they aren't clearly marked.
It is just as easy to confuse a Thomas Edison clump once the stems are cut back. Use a piece of garden twine or a zip tie to secure a label to the remaining stem handle immediately after cutting.
Digging Your Tubers with Care
Dahlia tubers grow in a clump that radiates outward from the main stem, much like a bunch of carrots or sweet potatoes. The "necks" of the tubers—the thin part where the tuber connects to the main stem—are very fragile. If a tuber breaks off at the neck, it will usually not be able to sprout the following year because the growth point, or "eye," is located on the stem tissue.
To dig them safely, follow these steps:
- Clear the perimeter: Start digging about 12 inches away from the main stem. This gives the tuber clump plenty of room so you don't slice through the roots.
- Use a garden fork: A garden fork is usually better than a shovel because it is less likely to slice through the tubers. It also allows the soil to fall through the tines.
- Lift gently: Insert the fork deep into the soil and gently pry upward. Work your way around the plant in a circle, loosening the soil from all sides.
- The final lift: Once the soil is loose, use the stem handle and the fork to lift the entire clump out of the hole.
Cleaning and Preparing for Storage
Once the clumps are out of the ground, you will likely have a fair amount of garden soil clinging to the roots. Some gardeners prefer to store their dahlias "dirty," believing the soil provides a protective layer. However, in most cases, it is safer to clean them. Soil can harbor pests and fungi that might cause rot during the long winter months.
Gently shake off the large clumps of dirt. You can use your hands or a small wooden stick to poke away the soil from between the tubers. For a more thorough cleaning, use a garden hose with a gentle spray setting to wash the tubers. This makes it much easier to see the condition of the roots and to identify any signs of damage or rot.
After washing, turn the clumps upside down. Dahlia stems are hollow and can hold a surprising amount of water. If this water sits in the crown of the plant, it can lead to crown rot. Letting them drain upside down for a few hours is a simple step that prevents big problems later.
Curing the Tubers
Before you pack them away, the tubers need to "cure" or dry slightly. This isn't the same as drying them out completely; you just want the outer skin to feel dry to the touch and any cut surfaces to callow over.
Place your cleaned clumps in a frost-free, shaded area with good air circulation. A garage, shed, or basement is perfect. Avoid direct sunlight, as this can cook the tubers or cause them to shrivel. Let them sit for 1 to 3 days. When the skin feels slightly leathery and the dirt is easy to brush off, they are ready for the next step.
To Divide or Not to Divide?
One of the most common questions we hear is whether to divide the tubers in the fall or wait until spring. There are benefits to both approaches.
Dividing in the fall:
- The tubers are softer and easier to cut.
- You save space in storage because you aren't storing "blind" tubers (those without an eye) or the old "mother" tuber.
- You can get the job done while the garden is fresh in your mind.
Dividing in the spring:
- The "eyes" (growth points) are much easier to see after the tubers have been in storage for a few months.
- There is less risk of rot, as you aren't creating fresh "wounds" right before putting them in a box for months.
- It is a great way to kick off the new gardening season.
For beginners, we often recommend waiting until spring to do the heavy dividing. However, you should always trim off the small, hair-like feeder roots and any tubers that are damaged, broken, or feel mushy. A healthy tuber should feel firm, like a fresh potato. If it feels like a soft sponge, it is best to discard it.
Key Takeaway: Use a sharp, sterilized knife or pruners when dividing. Ensure every piece you keep has a "neck," a "body," and a piece of the "crown" where the eye will sprout.
Selecting the Right Storage Container
The goal of winter storage is to keep the tubers dormant, cool, and slightly moist—but not wet. Think of it as keeping them in a "Goldilocks" state. If they are too dry, they will shrivel and die. If they are too wet, they will rot.
You can use several different types of containers for storage:
- Cardboard Boxes: These are excellent because they "breathe" and allow for some air exchange.
- Plastic Bins: If you use plastic, do not snap the lid shut tightly. Leave it cracked open to prevent moisture from building up and causing mold.
- Paper Bags: These are great for individual varieties, which can then be placed inside a larger crate.
- Milk Crates: These provide the best airflow but require a liner (like newspaper) to keep the storage medium from falling out.
Choosing a Storage Medium
To maintain the right moisture level, you should pack your tubers in a "medium." This material acts as insulation against temperature swings and helps regulate humidity.
Our favorite options include:
- Pine Shavings: Often sold as animal bedding, these are inexpensive, clean, and provide great airflow.
- Vermiculite: This mineral is excellent at holding just the right amount of moisture. It is a bit more expensive but very effective.
- Peat Moss: A classic choice, though it can be a bit dusty to work with. If it is bone dry, you may need to mist it very slightly.
- Coco Coir: An eco-friendly alternative to peat moss that holds moisture well.
Place a layer of your chosen medium in the bottom of your container. Lay the tubers or clumps on top, making sure they aren't touching each other if possible. This prevents rot from spreading from one tuber to another. Cover them with more medium and repeat the layers until the box is full.
Finding the Best Storage Location
Where you put your boxes is just as important as how you pack them. You are looking for a spot that stays consistently between 40°F and 50°F.
- Unheated Basements: Usually the best option, as they stay cool and relatively humid.
- Attached Garages: Can work well, but be careful that the temperature doesn't drop below freezing during a cold snap. You may want to place the boxes on a shelf or insulate them with blankets.
- Crawl Spaces: These often have the perfect temperature and humidity but can be difficult to access for checking on your plants.
Avoid storage spots near furnaces, water heaters, or wood stoves, as the dry heat will quickly shrivel the tubers. Likewise, avoid any area that is prone to flooding or high humidity, as this invites mold.
The Importance of Winter Check-ins
Storing dahlias is not a "set it and forget it" task. We recommend checking on your tubers about once a month. This only takes a few minutes but can save your entire collection.
Open your boxes and feel a few tubers.
- If they look shriveled or wrinkled: The environment is too dry. Use a spray bottle to lightly mist the storage medium with water. You don't want it wet, just slightly damp.
- If you see fuzzy mold or soft spots: The environment is too wet. Remove the affected tubers immediately. If the damage is small, you can cut off the rotten part and let the tuber air dry before putting it back. If the mold is widespread, leave the lid off the box for a few days to increase airflow.
- If you see sprouts: The storage area is too warm. Move the boxes to a cooler spot to keep the plants dormant until spring.
Mid-Winter Care Summary:
- Check tubers once a month for moisture levels.
- Remove any tubers that show signs of rot to prevent spreading.
- Mist the medium if tubers appear excessively wrinkled.
- Ensure the storage area remains between 40°F and 50°F.
Preparing for Spring
As the weather begins to warm in late March or April, you can bring your boxes out of storage. This is the perfect time to finish dividing your clumps if you didn't do it in the fall. By now, the "eyes" should be visible as small, pink or white bumps near the neck of the tuber.
If you want to get a head start on the season, you can "wake up" your tubers by potting them up indoors 4 to 6 weeks before the last frost date. If you'd like a spring planting refresher, our How to Plant Dahlias guide is a helpful companion. Place them in a warm, sunny spot and water them sparingly until you see green growth. This can lead to flowers much earlier in the summer. However, if you prefer a simpler approach, you can wait until the soil in your garden has warmed to 60°F and plant the dormant tubers directly into the ground.
Conclusion
Learning how to store dahlia tubers during the winter is one of the most useful skills a gardener can master. It transforms dahlias from a "one-season" purchase into a long-term investment that brings more joy every year. By following the natural cycle of the plant—waiting for frost, digging carefully, and providing a cool, stable resting place—you ensure that your garden will be filled with spectacular color again next summer.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to perform. Taking care of those tubers through the winter is simply the final step in a successful growing cycle. Gardening is a journey of learning and growth, and successfully overwintering your first batch of dahlias is a major milestone that every home gardener can achieve.
- Wait for frost to signal dormancy.
- Dig carefully to protect the fragile necks of the tubers.
- Store in a cool, dark place (40-50°F) in a breathable medium like pine shavings.
- Check monthly for rot or shriveling.
Key Takeaway: Winter storage is a simple way to preserve the plants you love. With just a little bit of care, your dahlias will return bigger and better every year.
We invite you to explore our selection of dahlia collections and other spring-planted bulbs to find the perfect additions to your landscape. With the right storage techniques, you can enjoy these stunning flowers for many seasons to come.
FAQ
Do I really have to dig up my dahlias every year?
If you live in USDA zones 8 or warmer, you may be able to leave your dahlias in the ground if the soil is well-draining. However, for most of the country (zones 3–7), the ground freezes deep enough to kill the tubers, so digging them up is necessary to keep them alive. Even in warm areas, many gardeners dig and divide them every few years to prevent the clumps from becoming overcrowded.
What is the best material to pack dahlia tubers in?
Pine shavings (animal bedding), vermiculite, and slightly damp peat moss are the most popular choices. These materials provide a balance of insulation and moisture control. The goal is to keep the tubers from drying out completely without trapping so much moisture that they begin to rot or grow mold.
My tubers look like they are shriveling in January. What should I do?
Shriveling is a sign that the storage environment is too dry or the medium has lost its moisture. Use a spray bottle to lightly mist the packing material (not the tubers directly) with water and close the box. If they are only slightly wrinkled, they will usually plump back up once they are planted in moist soil in the spring.
Can I store my dahlia tubers in the refrigerator?
While a refrigerator is cold enough, it is usually too dry and can actually "suck" the moisture out of the tubers. Additionally, some fruits and vegetables in the fridge release ethylene gas, which can damage the tubers' ability to sprout. An unheated basement or a cool closet is generally a much better environment for long-term storage.
