Introduction
Few garden experiences match the pure joy of seeing a dahlia garden in full bloom. From the massive, intricate petals of dinnerplate varieties to the perfectly symmetrical pompons, these plants are the undisputed stars of the summer and fall landscape. At Longfield Gardens, we believe that the beauty of these flowers shouldn’t have to be a one-season event. With a little bit of care and the right timing, you can easily save your dahlia tubers to grow again next year, allowing your collection to get better and more abundant every season.
This guide is designed for any gardener who wants to transition their dahlias from the garden bed to winter storage without the stress. We will walk you through the entire process, from the first frost until the tubers are tucked away for their winter nap. Whether you are a beginner or looking to refine your technique, we are here to help you succeed. For another way to plan ahead, browse our dahlia collections.
By understanding the simple steps of digging, cleaning, and storing, you can turn a single season of color into a lifetime of beautiful garden memories. Saving your tubers is a rewarding way to connect with the life cycle of your garden and ensure your favorite varieties return even stronger next summer. If you like compact blooms, take a look at our PomPon Dahlia collection.
Recognizing the Signal: When to Begin
The most common question gardeners ask is exactly when they should start the process of saving their dahlia tubers. The answer is usually provided by nature itself. Dahlias are native to the warm climates of Mexico and Central America, which means they are not built to survive freezing ground temperatures. For a broader overview, see All About Dahlias. However, they actually benefit from a light touch of cold before they head into storage.
In most regions, the signal to start is the first killing frost. You will know it has happened when your vibrant green plants suddenly turn dark brown or black overnight. While it might look a little sad to see the foliage go, this is actually a helpful turning point. The frost tells the plant to stop sending energy to the leaves and flowers and instead focus everything on the tubers underground. If you need the timing details, see when to bring dahlia bulbs in.
If you live in a climate where frost comes very late or not at all, you don't have to wait forever. Most growers aim to dig their tubers by mid-to-late November. The goal is to give the tubers as much time as possible to mature in the soil, as more mature tubers generally store much better through the winter.
Why the Wait Matters
Waiting for that first frost isn't just about timing; it’s about energy. Throughout the summer, the dahlia plant is busy building its root system. These roots, which we call tubers, are the storage tanks for the plant’s energy. The longer they stay in the ground, the more starches they can accumulate.
Once the top of the plant dies back, the "eyes"—the small bumps that will become next year’s sprouts—often become more prominent. This makes it much easier to see where the new growth will come from if you decide to divide your tubers before storing them.
What to Do Next: Timing Your Harvest
- Monitor your local weather forecast for the first "killing frost."
- Prepare your tools (loppers, garden fork, and labels) so they are ready when the temperature drops.
- Ensure all your dahlias are clearly labeled by variety while the flowers are still visible; once the plant turns black, it’s much harder to tell them apart.
- If a hard freeze (where the ground might freeze solid) is predicted, dig the tubers immediately, even if a light frost hasn't hit yet.
Key Takeaway: Let nature be your guide. Wait for the first frost to blacken the foliage, as this signals the tubers to toughen up and prepare for their winter dormancy.
Cutting and Curing: The First Steps
Once the frost has done its work, your next task is to manage the remaining stalks. At this stage, the plant is dormant, but the tubers are still very much alive. Before you reach for your shovel, you want to "cure" the tubers, and our how to care for dahlia bulbs guide covers that step.
Start by cutting the stalks down. Using a sharp pair of loppers or garden shears, cut the main stem so that only about 4 to 6 inches of stalk remains above the ground. This remaining piece of stem acts as a "handle" for the digging process and helps you keep track of where the center of the clump is located.
The In-Ground Curing Period
If your weather and soil conditions allow it, many experienced gardeners recommend leaving the cut-back clumps in the ground for about 5 to 7 days. During this week, the eyes on the tubers often begin to swell, making them easier to identify. More importantly, the tuber’s outer skin begins to set.
However, if your soil is very wet or if a deep, ground-penetrating freeze is expected, it is better to dig them up right away. Excess moisture is the primary enemy of a healthy tuber, as it can lead to rot before the storage process even begins.
Preventing Disease Spread
Dahlias can sometimes carry viruses that aren't always obvious during the peak of summer. To keep your garden healthy, it is a great habit to clean your cutting tools between plants. A quick dip in a solution of one part bleach to ten parts water is an easy win for plant health. This prevents any potential issues from moving from one clump to the next, ensuring that your entire collection stays as vibrant as the day you planted it.
The Gentle Dig: Lifting Without Damage
Digging up dahlia tubers is a bit like an archaeological dig; you want to be firm but incredibly gentle. The most important thing to remember is that dahlia tubers are attached to the central stem by a narrow "neck." This neck is very fragile. If the neck breaks or is severely creased, the tuber will likely fail to sprout next year, even if the rest of the tuber looks perfect.
Choosing the Right Tools
While a standard shovel can work, a garden fork (or pitchfork) is often the better choice. The tines of a fork allow you to loosen the soil without creating the solid "wall" of resistance that a shovel blade does. This reduces the risk of accidentally slicing through a stray tuber that grew further away from the main stalk than expected.
The Lifting Technique
To dig safely, start your fork about 10 to 12 inches away from the main stem. This "buffer zone" protects the outer tubers of the clump.
- Push the fork deep into the soil on all four sides of the plant.
- Gently pry upward to loosen the root ball from the surrounding earth.
- Once the soil is loose, use one hand to grasp the "stem handle" you left behind and the other hand to lift the clump from underneath with the fork.
Never try to yank the clump out by the stem alone. The weight of the soil attached to the tubers can easily snap those fragile necks. Instead, lift from below and let the soil fall away naturally.
Cleaning and Initial Drying
Once the tubers are out of the ground, they will likely be covered in a fair amount of garden soil. How you handle this depends on your soil type. If you have light, sandy soil, you might be able to simply brush the dirt away. If you have heavy clay, you may need a more thorough approach.
To Wash or Not to Wash?
There are two schools of thought on washing tubers. Some gardeners prefer to wash them completely clean with a garden hose to inspect for any signs of rot or insect damage. Others prefer to leave a little bit of soil on them, believing it helps maintain a more natural moisture level.
At our trial garden, we generally recommend washing the tubers if you plan to divide them in the fall. Clean tubers are much easier to work with, and you can clearly see the "eyes" and any potential problem spots. If you plan to store the clumps whole and divide them in the spring, a light brushing to remove the bulk of the dirt is usually sufficient.
The Drying Phase
After cleaning, the tubers need to dry—but not too much. Place the clumps in a protected area out of direct sunlight, such as a garage, a shed, or a covered porch. Turn them upside down so that any water trapped in the hollow stems can drain out.
Let them sit for 1 to 3 days until the exterior feels dry to the touch. You don't want them to stay out so long that they begin to shrivel or look like raisins. The goal is "dry on the outside, firm on the inside."
What to Do Next: Preparation Steps
- Shake off large clumps of soil immediately after digging.
- If washing, use a gentle stream of water to avoid bruising the skin.
- Label every clump immediately with a waterproof marker or a tied-on tag.
- Trim off any long, thin "hair roots" and remove the "mother tuber" (the original tuber you planted in the spring) if it looks soft or spent.
Understanding the Anatomy: Finding the Eyes
If you want to divide your dahlias—either to create more plants or simply to save space in storage—you must understand how they grow. For a closer look at the anatomy of healthy tubers, see Dahlia Tubers: What You Need to Know.
Unlike a potato, where an eye can grow from almost anywhere on the tuber, a dahlia tuber will only sprout if it has a piece of the "crown" attached.
The crown is the area where the tuber meets the main stem. The "eye" is a small, often pinkish or green bump located right on that crown. If you cut a tuber off but don't get a piece of the crown with an eye, that tuber will never grow a new plant. It’s a common mistake for beginners, but once you see your first eye, you’ll know exactly what to look for every time.
Fall vs. Spring Dividing
You can divide your dahlias in the fall or wait until the spring.
- Fall Dividing: It’s easier to cut the tubers while they are still somewhat soft. It also saves a lot of space in your storage containers.
- Spring Dividing: The eyes are much easier to see in the spring as they begin to wake up. This is a great option if you find it difficult to locate the eyes in the fall.
Regardless of when you choose to divide, the rule is the same: each division must have at least one healthy tuber, a solid neck, and a piece of the crown with a visible eye.
Storage Mediums: Choosing the Right Home
The goal of winter storage is to keep the tubers dormant, cool, and just slightly hydrated. If they get too wet, they rot. If they get too dry, they shrivel and die. Choosing the right storage medium helps balance these conditions.
Peat Moss or Coconut Coir
These are very popular choices because they are excellent at regulating moisture. You can buy a bag of slightly damp (not wet) peat moss and pack the tubers into boxes or bins, layering the moss so the tubers don't touch each other.
Vermiculite
Vermiculite is a mineral that holds onto moisture very effectively. It is often a favorite for gardeners who live in very dry climates. Like peat moss, you simply nestle the tubers into the vermiculite inside a container.
Wood Shavings
Pet bedding (pine shavings) is a cheap and effective storage medium. It provides great air circulation and a bit of insulation. If you use shavings, you may need to check your tubers more often to ensure they aren't drying out, as shavings don't hold as much moisture as peat or vermiculite.
The Plastic Wrap Method
Some gardeners have great success by cleaning and drying individual tubers and then wrapping them tightly in plastic kitchen wrap (the "Saran Wrap method"). This seals the moisture inside the tuber itself. It’s a space-saving method, but it requires that the tubers be perfectly clean and dry on the outside to prevent trapping mold.
The Perfect Environment: Temperature and Humidity
Where you put your storage containers is just as important as how you pack them. Tubers are very specific about their preferred "winter bedroom."
The "Goldilocks" Temperature
The ideal temperature for storing dahlia tubers is between 40°F and 50°F (4°C to 10°C).
- Too Cold: If the temperature drops below 32°F, the water inside the tubers will freeze, causing the cell walls to burst. When they thaw, they will turn into a mushy, black mess.
- Too Warm: If the temperature stays above 50°F, the tubers may think it’s spring and start to sprout prematurely. They may also dry out much faster in a warm environment.
A cool basement, an unheated crawlspace, or a frost-free garage are usually the best spots. Avoid placing them near a furnace, water heater, or on a cold concrete floor that might transmit freezing temperatures from the ground.
Managing Humidity
Dahlias prefer high humidity—around 80% to 90%—to keep from shriveling. Since most homes are much drier than that in the winter, the storage medium (like the peat moss mentioned above) does the heavy lifting. Using a plastic bin with a lid that is slightly ajar can help trap some humidity while still allowing for a small amount of air exchange.
Key Takeaway: Success in storage is all about balance. Aim for a cool, dark, and slightly humid spot where the temperature stays consistently above freezing but below 50°F.
Winter Maintenance: The Monthly Checkup
One of the biggest mistakes gardeners make is "setting and forgetting" their tubers. Storage is a dynamic process, and things can change over the winter. We recommend checking your tubers once a month.
What to Look For
When you open your storage bins, look for two things:
- Signs of Rot: If you see any tubers that have become soft, mushy, or smell bad, remove them immediately. Rot can spread from one tuber to another, and removing a "bad apple" can save the rest of the bunch.
- Signs of Shriveling: If the tubers look like wrinkled skin or feel very light and hollow, they are losing too much moisture. You can remedy this by lightly misting the storage medium with a spray bottle of water. You don't want it wet—just a tiny bit of dampness to restore the humidity.
Keeping Your Cool
If you notice your dahlias are starting to grow long, white sprouts in January or February, they are likely too warm. Move the bin to a cooler part of the house to slow them down. If you're planning next season's display, the Dahlia Dinnerplate High Summer Mix is a colorful option.
Safety and Expectations
While dahlia tubers are exciting to save, it is important to handle them with care. Many garden plants, including dahlias, can be toxic if ingested by pets or small children. Always store your tubers in a secure location that is out of reach of curious paws and hands.
It is also important to have realistic expectations. Even professional growers don't always have a 100% success rate with winter storage. Factors like the specific variety, the weather during the growing season, and the humidity of your home all play a role. If you save ten tubers and eight of them make it through to spring, consider that a massive success!
At Longfield Gardens, we test many varieties in our trial gardens to see which ones are the most robust. If you're looking for a dependable mix for next season, the Dahlia Assorted Harvest Collection is a great place to start.
Conclusion
Saving dahlia tubers is one of the most satisfying "circular" tasks in the garden. It transforms a seasonal purchase into a long-term investment in your landscape’s beauty. By following the simple rhythm of the seasons—waiting for the frost, digging with care, and providing a cool, dark winter home—you can enjoy your favorite flowers year after year.
At Longfield Gardens, we want you to feel confident in every step of your gardening journey. Whether you are storing a few special tubers or an entire field’s worth of color, the process is an opportunity to slow down and appreciate the resilience of nature.
- Wait for the first frost to signal the start of the harvest.
- Dig carefully with a fork to protect the fragile necks of the tubers.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly for rot or shriveling to ensure a healthy spring start.
"The effort you put into saving your tubers during the quiet winter months is repaid tenfold when the first magnificent blooms of summer arrive."
We look forward to seeing your garden grow even more beautiful with each passing year. For more inspiration and the highest quality tubers to add to your collection, feel free to explore our planting guides and seasonal selections, including the Dahlia Dinnerplate Summer Lovin Collection.
FAQ
Can I leave my dahlia tubers in the ground all winter?
This depends entirely on your USDA Hardiness Zone Map. In zones 8 and warmer, dahlias can often stay in the ground if the soil is well-draining and you provide a thick layer of mulch. In zones 7 and colder, the ground will freeze deep enough to kill the tubers, so they must be dug up and stored indoors.
Do I have to wash the dirt off the tubers before storing them?
While not strictly required, washing makes it much easier to inspect for rot and find the "eyes" for dividing. If you choose not to wash them, at least brush off the excess soil once it has dried to prevent trapping too much moisture against the skin, which can lead to fungal issues.
My tubers look shriveled in mid-winter. Are they dead?
Not necessarily. Slight shriveling is common as tubers lose moisture. If they still feel somewhat firm when squeezed, they are likely still viable. Lightly mist the storage medium (like peat moss) with water to increase humidity, but avoid making the tubers themselves wet.
What should I do if I find mold on my tubers during a checkup?
If you find a small amount of surface mold, wipe it off with a cloth dipped in a weak bleach solution and allow it to air dry. If the tuber is soft or mushy, it is rotting and should be thrown away immediately to prevent the rot from spreading to healthy tubers in the same bin. If you run into ongoing problems, please review our 100% Quality Guarantee.
