Introduction
There is a special kind of magic that happens in the garden during late summer and early autumn. While other flowers may begin to fade, dahlias take center stage with their bold colors and intricate shapes. From the massive petals of dinnerplate dahlias to the perfectly symmetrical pompon types, these plants are often the highlight of the season. At Longfield Gardens, we believe that the only thing better than enjoying a beautiful dahlia bloom is knowing you can enjoy that same plant again next year.
Saving dahlia tubers is one of the most rewarding skills a gardener can learn. While dahlias are often called "bulbs," they are technically tubers—thick, potato-like roots that store energy for the plant. Because these plants are native to the warm climates of Mexico and Central America, they cannot survive freezing winter temperatures in most parts of the United States. Learning how to save dahlia bulbs allows you to protect your favorite varieties and even expand your garden for free as the tubers multiply each season. By following a few basic rules, you can ensure your dahlia collections continue to thrive and grow.
This guide will walk you through the simple steps of digging, cleaning, and storing your dahlias so they stay healthy until spring. Whether you are a busy beginner or a seasoned grower, these practical tips will help you preserve your garden's beauty year after year. For a fuller overview of planting and growing, see All About Dahlias.
When to Start Saving Dahlia Bulbs (Timing)
Success with dahlias begins with getting the timing right. In many gardening tasks, being early is a virtue, but with dahlias, patience is your best friend. The tubers spend the entire summer growing and storing starches that will fuel next year’s growth. If you dig them up too early, they may not have enough stored energy to survive the long winter months in storage.
For most gardeners in zones 7 and colder, the signal to start the process is the first "killing frost." If you need help locating your USDA zone, the Hardiness Zone Map makes it easy. This occurs when temperatures drop low enough to turn the green foliage of the dahlia black or dark brown. This usually happens in October or November, depending on your local weather. While the top of the plant looks finished, the tubers underground are perfectly safe and are actually undergoing a final ripening process.
Some gardeners prefer to wait a week or two after the first frost before digging. This short waiting period signals the plant to go into "dormancy," which is a deep sleep that helps the tubers stay fresh and firm during storage. If you live in a very wet climate, you might choose to dig sooner to avoid the risk of rot, but waiting for that first frost is the gold standard for healthy tubers.
Key Takeaway: Wait for the first frost to turn the foliage black before you begin digging. This ensures the tubers are mature and ready for winter dormancy.
Preparing to Dig Your Dahlias
It is incredibly easy to lose track of which tuber belongs to your favorite Cafe Au Lait variety.
That is especially true for Thomas Edison. Start by checking your garden map or the tags you placed in the spring. If the tags have faded, rewrite them with a waterproof marker. You can tie these tags directly to the base of the stems. This ensures that every clump is identified before it ever leaves the soil.
Once your labels are secure, you can cut back the foliage. Use a pair of sharp loppers or garden snips to cut the main stalks down to about 4 to 6 inches above the ground. This remaining stem acts as a handle during the digging process and helps you keep track of where the "eyes" (the growth points) are located.
Essential Tools for the Job
You do not need a shed full of expensive equipment to save your dahlias. A few basic tools will make the process much easier:
- Garden Fork: This is the best tool for the job because the tines allow you to lift the soil without the high risk of slicing through the tubers like a shovel might.
- Waterproof Marker: For labeling tubers or tags.
- Garden Hose: To wash away soil so you can inspect the health of the clump.
- Sharp Snips or Pruners: For cutting back the stalks and trimming small "feeder" roots.
A Step-by-Step Guide to Digging Tuber Clumps
Dahlia tubers are surprisingly fragile. The "neck" of the tuber—the thin part that connects the fat body to the main stem—is easily broken. If the neck snaps, the tuber usually cannot grow a new stem next year. Approach the digging process with a gentle hand and a bit of space.
Start by placing your garden fork about 12 inches away from the main stem. This ensures you aren't stabbing into the heart of the tuber clump. Gently push the fork into the soil and lean back to loosen the earth. Work your way around the plant in a circle, loosening the soil on all sides.
Once the soil is loose, use the fork to pry the entire clump upward from beneath. Use one hand to steady the "stem handle" you left behind, but do not yank on it. Let the tool do the heavy lifting. As the clump clears the ground, gently shake off the largest chunks of soil.
What to do next:
- Lift the clump carefully and set it on the grass or a workspace.
- Avoid dropping the clumps, as the weight of the wet soil can snap the fragile necks.
- Turn the clump upside down for a few minutes to allow any water trapped in the hollow stems to drain out.
Cleaning and Curing Your Dahlia Tubers
Once your dahlias are out of the ground, they need a bit of cleaning. Soil contains bacteria and fungi that can lead to rot during the winter. A quick wash with a garden hose is usually enough to remove the bulk of the dirt. If you have very sandy soil, you might be able to simply brush it off with your hands after it dries.
After washing, inspect the clump. Use your snips to trim away the long, hair-like feeder roots. These roots are not needed for storage and can often hold onto excess moisture. You should also look for any tubers that were damaged during the digging process. If a tuber is sliced open or has a broken neck, it is best to remove it now so it doesn't rot and affect the rest of the healthy clump.
The next step is "curing." This is a simple but vital part of saving dahlia bulbs. Curing allows the skin of the tuber to toughen up, much like a potato. Place your cleaned clumps in a cool, dry place out of direct sunlight. A garage, basement, or covered porch works well. Let them sit for 1 to 3 days. You don’t want them to shrivel, but you do want the outer surface to feel dry to the touch.
Key Takeaway: Curing your tubers for a few days toughens the skin and prepares them for a successful winter in storage.
Dividing Dahlia Tubers: Fall vs. Spring
One of the most common questions gardeners ask is whether they should divide their dahlia clumps into individual tubers in the fall or wait until the spring. Both methods work, and the choice often depends on how much storage space you have.
Dividing in the Fall
If you have a large collection and limited storage space, dividing in the fall is a great option. Individual tubers take up much less room than large, bulky clumps. Another benefit is that the tubers are softer and easier to cut in the autumn. However, it can be harder to see the "eyes" in the fall, which means you might accidentally keep a tuber that isn't viable.
Dividing in the Spring
Many home gardeners prefer to store the entire clump and divide it in the spring. Storing the clump whole often protects the tubers from drying out too quickly. By springtime, the "eyes" will begin to swell and may even start to sprout, making it very easy to see exactly where to make your cuts.
If you choose to divide your tubers, remember to sanitize your cutting tools between different plants. A quick dip in a solution of one part bleach to ten parts water helps prevent the spread of garden diseases from one variety to another.
How to Identify a Viable Tuber (Body, Neck, and Eye)
When you look at a dahlia clump, you are looking at a cluster of potential new plants. For a deeper primer on tuber anatomy, see Dahlia Tubers: What You Need to Know. However, not every part of the clump will grow. For a single tuber to be "viable"—meaning it can grow into a blooming plant—it must have three specific parts:
- The Body: This is the fat, potato-like part that holds the nutrients. It should be firm, not mushy.
- The Neck: This is the narrow connection between the body and the crown. It must be intact and unbroken.
- The Eye: This is the most important part. The eye is a small bump or "bud" located on the crown (the area where the tuber meets the main stem). This is where the new sprout will emerge.
If a tuber has a great body and a strong neck but no eye, it will never grow a stem. It is helpful to think of the eye like the "eye" of a potato. If you aren't sure if a tuber has an eye, it is always better to leave it attached to a larger piece of the crown just to be safe.
Choosing the Best Storage Method for Your Space
There is no "one size fits all" way to store dahlias. If you want a step-by-step video companion, How to Lift and Store Dahlia Bulbs is a helpful reference. The best method for you depends on your local humidity and the temperature of your storage area. The goal is to keep the tubers in a state of suspended animation: not so dry that they shrivel into raisins, and not so wet that they turn into mush.
The Bin and Bedding Method
This is the most popular method for home gardeners. You place your tubers or clumps in a plastic bin or cardboard box and surround them with a packing medium. This medium helps regulate moisture.
- Vermiculite: Excellent for maintaining a steady moisture level.
- Peat Moss: A classic choice that is slightly acidic and helps prevent rot.
- Wood Shavings: Often used for pet bedding, these are inexpensive and provide good insulation.
When using this method, place a layer of bedding at the bottom, add a layer of tubers (making sure they don't touch each other), and then cover them with more bedding. Repeat this until the bin is full. If you use a plastic bin, keep the lid slightly cracked or drill a few small holes for air circulation.
The Plastic Wrap Method
Some gardeners have great success wrapping individual, clean tubers tightly in plastic kitchen wrap. This seals in the tuber's natural moisture. These wrapped tubers can then be placed in boxes and stored. This is a space-saving method, but it requires that the tubers be perfectly clean and dry on the surface before wrapping to prevent mold.
The Paper Bag Method
If you live in a high-humidity area, plastic may trap too much moisture. In this case, wrapping clumps in several layers of newspaper or placing them in brown paper bags can work well. The paper allows the tubers to breathe while providing a bit of protection from the cold.
Ideal Storage Conditions: Temperature and Humidity
Once your dahlias are packed, they need a "Goldilocks" environment. The ideal temperature for storing dahlia tubers is between 40°F and 45°F.
If the temperature drops below freezing (32°F), the water inside the tubers will freeze, causing the cell walls to burst. When they thaw, they will turn into a black, watery mess. On the other hand, if the temperature stays above 50°F, the tubers may think it is springtime and begin to sprout prematurely, or they may dry out too quickly.
A cool basement, an unheated (but attached) garage, or a root cellar are usually the best spots. Avoid storing them near a furnace or in a spot that gets a lot of draft. Humidity is also a factor. Most tubers prefer a humidity level of about 80%. If your storage area is very dry, you might need to lightly mist your packing medium with water once or twice during the winter.
Key Takeaway: Keep your storage area between 40°F and 45°F. Use a simple thermometer to monitor the spot and ensure your tubers don't freeze.
Caring for Your Tubers During the Winter Months
Saving dahlia bulbs isn't a "set it and forget it" task. If you'd like a fuller winter-care walkthrough, How to Overwinter Dahlias covers the process well. It is a good idea to check on your "sleeping" dahlias once a month. This small effort can save your entire collection if something starts to go wrong.
When you check your tubers, look for two things: rot and shriveling.
- If you see rot: Rot usually looks like fuzzy mold or a dark, soft spot. If you catch it early, you can simply cut away the affected part with a clean knife and throw the bad piece in the trash. This prevents the rot from spreading to the healthy tubers.
- If you see shriveling: If the tubers are starting to look wrinkled like a prune, they are too dry. Use a spray bottle to lightly mist the packing medium (vermiculite or peat moss). You don't want it to be wet, just slightly damp to the touch.
By spending ten minutes once a month checking your bins, you ensure that your dahlias arrive in spring healthy and ready to grow.
Dahlias can be toxic to dogs and cats if they are eaten. While it is rare for a pet to chew on a dormant tuber, it is best to keep your storage bins on a shelf or in a closed area where curious pets cannot reach them.
Conclusion
Saving your dahlia tubers is one of the most satisfying ways to bridge the gap between gardening seasons. It turns a one-time purchase into a lifelong collection and gives you the chance to share your favorite varieties with friends and neighbors. While the process of digging and storing might seem detailed, it really comes down to a few simple principles: wait for the frost, keep them cool and dry, and check on them occasionally.
As you look forward to the next growing season, remember that every tuber you save is a head start on a more beautiful garden. If you want to keep exploring options for next year, browse our Dahlia Collections. At Longfield Gardens, we love seeing how home gardeners use these simple steps to preserve the flowers they love. There is nothing quite like the feeling of pulling a firm, healthy tuber out of storage in the spring and seeing that first green sprout begin to emerge.
- Label your plants before the frost so you don't lose track of varieties.
- Dig carefully with a garden fork to avoid damaging the fragile necks.
- Store in a cool, dark place between 40°F and 45°F.
- Check your tubers monthly for rot or shriveling to ensure success.
Saving dahlia tubers is a simple way to protect your investment and ensure your garden is even more spectacular next year than it was this year.
The next step is to plan your space for next year. While your tubers are resting, you can browse Dahlia Dinnerplate High Summer Mix to add new colors and shapes to your collection. When spring finally arrives and the soil warms up, you'll be ready to plant your saved treasures and enjoy another season of incredible blooms.
FAQ
Can I leave my dahlia tubers in the ground all winter?
In USDA hardiness zones 8 and warmer, you can often leave dahlias in the ground if the soil provides good drainage. However, in zones 7 and colder, the ground will freeze deep enough to kill the tubers. For most US gardeners, digging them up is the only way to ensure they survive until next year.
What if I don't have a basement or a garage for storage?
If you don't have a traditional cool storage spot, you can get creative. Some gardeners use a cool closet in a mudroom or even a dedicated "beverage fridge" set to 45°F. The key is to avoid areas that experience large temperature swings, like an attic or a shed that isn't insulated.
Why did my tubers turn to mush in storage?
Mushy tubers are usually a sign of rot caused by too much moisture or freezing temperatures. If the tubers were wet when they were packed, or if the storage bin didn't have enough air circulation, fungus can take hold. Always ensure tubers are dry to the touch before packing and that they never drop below freezing.
How do I know if a tuber is still good in the spring?
A healthy tuber should feel firm, similar to a fresh potato. If it feels hollow, extremely light, or squishy, it has likely either dried out or rotted. In late spring, you should also see a small green or pink "eye" starting to sprout near the neck, which is a sure sign that the tuber is ready to be planted.
