Introduction
Few moments in the garden are as rewarding as seeing the first dinnerplate dahlia unfurl its massive, intricate petals in late summer. These plants are the heavy hitters of the flower world, providing a spectacular show of color right up until the first frost. Because dahlias are native to the warm mountain regions of Mexico, they cannot survive freezing temperatures in the ground in most parts of the United States. To enjoy these same beautiful blooms year after year, you simply need to tuck them away safely for the winter.
At Longfield Gardens, we want to help you feel confident about every step of the dahlia lifecycle, and our Dahlia Collections page can help you plan what to grow next. Winter storage is often the part that feels most mysterious to new gardeners, but it is actually quite straightforward once you understand the basic needs of the tubers. This guide will walk you through the best containers and packing materials to ensure your dahlias emerge healthy and ready to grow when spring returns.
The key to success is finding a balance between keeping the tubers dry enough to prevent rot and moist enough to prevent shriveling. By choosing the right storage medium and environment, you can protect your investment and look forward to an even bigger display next season. For a full step-by-step refresher, see our How to Store Dahlia Tubers in Winter guide.
Preparing Tubers for Storage
Before you decide what to store your dahlia tubers in, they must be properly prepared. The preparation process ensures that you aren't bringing excess moisture or garden pests into your storage containers. Timing is your first priority. In most regions, we recommend waiting until a killing frost has blackened the foliage. This frost signals the plant to go dormant and direct its energy into the tubers, which helps them "cure" or toughen up for the winter months.
Once the foliage has turned brown or black, cut the stems down to about four inches. It is helpful to leave the tubers in the ground for about a week after cutting the stems, provided the ground isn't expected to freeze solid. This short waiting period encourages the "eyes" or growth points to become more visible, which is helpful if you plan to divide your tubers before packing them away. For a closer look at clumps, eyes, and individual tubers, see Dahlia Tubers: What You Need to Know.
When you are ready to dig, use a garden fork rather than a shovel. Start your digging circle at least a foot away from the main stem to avoid slicing through the tubers. Gently lift the entire clump and shake off the loose soil. Some gardeners prefer to wash their tubers with a garden hose to remove all dirt, while others prefer to let them dry and simply brush the dirt off. If you do wash them, ensure they are completely dry before they go into any container. Lay them out in a frost-free, shaded area like a garage or basement for 24 to 48 hours. This drying period is essential to prevent mold from forming once they are packed.
Key Takeaway: Success starts with dryness. Ensure your tubers are dry to the touch and the hollow stems have had a chance to drain before you place them in their winter home.
Choosing the Best Storage Containers
The container you choose acts as the first line of defense against fluctuating temperatures and humidity. There is no single "perfect" container because your choice depends largely on the environment of your storage space. The goal is to create a microclimate that stays stable even if the air in your basement or garage changes.
Cardboard Boxes
Cardboard boxes are a classic choice for many home gardeners. They are breathable, which allows for some air exchange and prevents moisture from being trapped against the tubers. This breathability is a major benefit if your storage area is naturally a bit damp, as the cardboard can absorb a small amount of excess humidity. However, if your storage area is very dry, like a heated basement, cardboard might allow the tubers to dry out too quickly.
Plastic Bins and Totes
Plastic bins are excellent for gardeners who store their dahlias in a dry environment. They do a great job of holding in moisture, which prevents the tubers from shriveling. The most important rule when using plastic is to provide ventilation. We recommend drilling several small holes in the sides or the lid of the bin to allow for minimal air circulation. If a plastic bin is sealed airtight, any remaining moisture on the tubers will cause them to rot within weeks.
Paper Bags
For those with limited space or a small number of tubers, heavy-duty paper bags are a practical option. Paper bags offer the same breathability as cardboard but are easier to tuck into small corners. Many gardeners like to place individual varieties in their own paper bags and then group those bags into a larger crate or box. This keeps varieties organized and provides an extra layer of insulation.
Nursery Crates or Milk Crates
Open-sided crates provide the maximum amount of airflow. These are ideal if you have a storage space with very high humidity, such as a dedicated root cellar. Because the sides are open, you will need to use a thick layer of storage medium, like wood shavings, to ensure the tubers aren't directly exposed to the air.
What to do next:
- Assess your storage space: Is it damp (like a cellar) or dry (like an attached garage)?
- Select a container that balances your environment: Plastic for dry spots, cardboard or paper for damp spots.
- Clean your containers before use to ensure no old soil or mold spores are present.
- Label every container with the dahlia variety name and the date you packed them.
The Best Storage Mediums
What you pack around the tubers is just as important as the container itself. The storage medium serves two purposes: it cushions the tubers to prevent physical damage and it regulates moisture. At Longfield Gardens, we have found that different mediums work better for different gardening styles and climates.
Vermiculite
Vermiculite is widely considered the gold standard for dahlia storage. It is a naturally occurring mineral that has been heated until it expands into light, absorbent flakes. It is excellent at holding a tiny amount of moisture without feeling "wet." If you are a beginner, vermiculite is a very forgiving medium because it naturally resists mold and fungi. It is lightweight and easy to pour around the nooks and crannies of a large tuber clump.
Peat Moss
Peat moss is another popular choice and is easily found at any garden center. It is slightly acidic, which can help inhibit the growth of certain types of rot. When using peat moss, it should be bone-dry or only very slightly damp. If the peat moss feels wet to the touch, it will likely cause the tubers to decay. One downside to peat moss is that it can be quite dusty to work with, so many gardeners prefer to wear a mask when packing their bins.
Pine or Cedar Shavings
The shavings used for animal bedding are an affordable and effective storage medium. Cedar shavings, in particular, have natural antifungal properties and a pleasant scent. Shavings provide excellent insulation and are great at absorbing minor fluctuations in humidity. They don't pack as tightly as vermiculite or peat moss, which allows for a bit more air to reach the tubers. This is often a good thing, as it prevents "hot spots" of moisture from forming.
Newspaper
If you are looking for a low-cost, readily available option, shredded or bundled newspaper works surprisingly well. You can wrap individual tubers in several layers of newspaper or use shredded paper to fill the gaps in a box. Newspaper is quite dry, so this method is best suited for environments that aren't overly arid. If you find your tubers are shriveling in paper, you can lightly mist the paper with a spray bottle once a month.
Clean Sand
Storing tubers in sand is a very old-fashioned method that still works today. Sand provides a very stable temperature environment and prevents the tubers from touching each other. However, sand is extremely heavy. A large plastic bin filled with sand and tubers can be difficult to move. If you choose sand, ensure it is clean "play sand" rather than horticultural sand which might contain salts or other additives.
"The goal of a storage medium is to act like a buffer. It should protect the tubers from the dry air while ensuring they never sit in standing moisture."
Environmental Factors for Winter Success
Even the best container and medium can't save tubers if the environment is wrong. Dahlias need a "Goldilocks" zone to stay dormant but alive.
Temperature
The ideal temperature for dahlia storage is between 40°F and 50°F. If the temperature drops below freezing (32°F), the water inside the tuber cells will freeze, expand, and burst the cell walls. When the tuber thaws, it 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 is time to grow and will begin to sprout prematurely, or they may simply dry out and die from the heat. If you're not sure how your region lines up, the Hardiness Zone Map is a useful reference.
Unheated basements, crawl spaces, or insulated garages are usually the best spots. Avoid placing your containers directly on a concrete floor, as concrete can pull moisture out of the containers or conduct cold from the ground. Placing your boxes on a wooden pallet or a shelf is a much safer approach.
Humidity
Humidity is the most challenging variable to control. Ideally, you want a relative humidity of about 70% to 80%. In most homes during the winter, the air is much drier than this due to heating systems. This is why we use storage mediums and lids. If you notice your tubers are starting to look wrinkled like a prune, the humidity is too low. If you see fuzzy white or gray mold growing on the surface, the humidity is too high or there is not enough airflow.
Dividing vs. Storing Whole Clumps
A common question we hear is whether it is better to divide the tubers into individual pieces in the fall or store the entire clump as it came out of the ground. Both methods have advantages.
Storing Whole Clumps
Storing the entire clump is the easiest method for the busy gardener. It requires less work in the fall when there are many other garden chores to finish. Large clumps also tend to hold their moisture better than individual tubers because there is less surface area exposed to the air. The main drawback is that clumps take up significantly more space. If you have dozens of dahlias, storing whole clumps might require a very large storage area.
Storing Individual Tubers
Dividing in the fall allows you to fit many more dahlias into a single box. It also gives you a chance to inspect each tuber closely for signs of damage or disease. When you divide, you must ensure that each individual tuber has an "eye"—the small bump where the new stem will grow. Without an eye, a tuber will never produce a plant, even if it looks healthy. For a broader overview of how dahlias grow, see All About Dahlias.
If you choose to divide in the fall, let the cut ends of the tubers "callous" over for 24 hours before packing them. This creates a dry scab that prevents rot from entering the fresh cut.
Checklist for Packing:
- Place a 2-inch layer of medium at the bottom of your container.
- Arrange tubers or clumps so they are not touching each other.
- Cover with more medium, ensuring all gaps are filled.
- If stacking layers, place another 2 inches of medium between each layer.
- Close the lid (or fold the bag) but do not seal it airtight.
Mid-Winter Maintenance
Gardening is a year-round activity, even when the plants are dormant. We recommend checking on your stored dahlias once a month. This small habit can be the difference between losing a few tubers and losing your entire collection.
Open your containers and feel a few of the tubers. They should feel firm, like a fresh potato. If you find one that is soft or smelling bad, remove it immediately. Rot can spread quickly from one tuber to its neighbors. If you notice a small amount of surface mold, you can often wipe it off and leave the container open for a day to let some moisture escape.
If the tubers look shriveled, you can lightly mist the storage medium with water. Be careful not to overdo it; you just want to add a hint of moisture to the air inside the box, not soak the tubers. Most gardeners find that they only need to do this once or twice during a particularly cold, dry winter.
Common Myths and Simple Fixes
In the world of gardening, there are many "hacks" that can actually do more harm than good. One common suggestion is to wrap tubers in plastic wrap. While some gardeners have success with this, it is very risky for beginners. Plastic wrap traps every bit of moisture inside, and if the tuber wasn't 100% dry, it will rot almost instantly. We find that the "breathable" methods using mediums like vermiculite are much more reliable.
Another myth is that you need to use fungicides or chemical powders to keep tubers healthy. While professionals sometimes use these, they are usually unnecessary for the home gardener. Good hygiene, proper drying, and the right temperature are far more effective than any chemical shortcut. If you start with healthy, firm tubers and keep them in the right environment, nature will do the rest of the work for you.
Realistic Expectations for Overwintering
It is important to remember that even with perfect care, not every tuber will make it through the winter. This is a natural part of gardening. Sometimes a tuber has a hidden bit of damage from the growing season, or a particular variety is simply less hardy than others. If you lose 10% to 15% of your tubers over the winter, you are actually doing very well.
Weather plays a huge role. A particularly bitter winter might make your garage colder than usual, or a warm spell in February might cause tubers to wake up early. Don't be discouraged by these fluctuations. Part of the joy of gardening is learning how your specific microclimate behaves and adjusting your methods over time.
Conclusion
Storing dahlia tubers is a rewarding bridge between the seasons. By taking a little time in the late autumn to pack your tubers away in the right container and medium, you ensure that the beauty of your summer garden isn't lost to the winter cold. Whether you choose the moisture-retentive qualities of a plastic bin with vermiculite or the breathability of a cardboard box with wood shavings, the goal is simply to keep your dahlias dormant, cool, and hydrated. For a color-coordinated mix of large flowering dahlias, browse the Dahlia Dinnerplate Summer Lovin Collection.
At Longfield Gardens, we believe that every gardener can master this process with a bit of practice. The satisfaction of pulling firm, healthy tubers out of their winter boxes in the spring is almost as wonderful as seeing the flowers themselves. For more choices, shop our Dahlias for Sale.
- Wait for the frost to signal dormancy before digging.
- Ensure tubers are dry and clean before packing.
- Choose a container and medium that match your storage environment.
- Check your tubers monthly to catch any issues early.
"Winter storage is not about stopping life; it is about protecting the potential for a beautiful spring."
As the weather begins to cool, take a look at your storage options and prepare your supplies. With your tubers tucked away safely, you can spend the winter planning your next garden layout, knowing that your favorite dahlias will be ready to join you once the soil warms up again. If you want a broader range of bloom forms, browse Decorative Dahlias.
For another color-coordinated dinnerplate option, see the Dahlia Dinnerplate Cloud Nine Collection.
FAQ
Can I store dahlia tubers in the refrigerator?
While a refrigerator maintains the correct temperature (40-45°F), it is generally not recommended for long-term storage because the air inside is extremely dry. Additionally, ripening fruits and vegetables in the fridge release ethylene gas, which can damage the tubers or prevent them from sprouting in the spring. If you must use a fridge, use a dedicated one and place the tubers in a sealed plastic bag with plenty of moist vermiculite. For spring planting depth, see How Deep Do I Plant Dahlia Bulbs?.
What happens if I forget to dig my dahlias up before the ground freezes?
If the ground freezes solid before you dig the tubers, they will likely die. However, if only the top inch or two of soil has crusted over, the tubers might still be safe. Dig them as soon as possible, inspect them for mushy spots, and dry them thoroughly. It is always better to dig a little early than to wait too long and risk a deep freeze.
Do I need to wash the dirt off the tubers before storing them?
There are two schools of thought on this, and both work. Washing them makes it much easier to see the "eyes" and any signs of rot or insect damage. However, you must be absolutely certain they are 100% dry before packing. Leaving the dirt on is faster and provides a small extra layer of protection, but it can hide problems and makes the packing process much messier.
Why are my dahlia tubers turning soft and smelling bad?
Soft, smelly tubers are a sign of rot, which is usually caused by too much moisture or bacteria entering a wound. This can happen if the tubers weren't dried enough before storage or if the storage medium is too wet. If you find a rotten tuber, throw it away immediately and check the surrounding tubers for signs of spread. Increasing the airflow in your storage container can help prevent further issues.
