Introduction
The first time you see a dinnerplate dahlia in full bloom, it feels like a gardening miracle. These spectacular flowers, with their intricate petals and vibrant colors, are the highlight of the late-summer garden. When the season begins to wind down, many gardeners find themselves wishing they could keep that beauty around for another year.
The good news is that you absolutely can. While we often call them "bulbs," dahlias actually grow from tubers. In most parts of the United States, these tubers cannot survive the freezing winter ground, but they are very easy to lift and store. At Longfield Gardens, we want to help you enjoy these stunning flowers year after year by mastering the simple art of overwintering.
In this guide, we will walk you through the straightforward steps to dig, clean, and store your dahlia tubers. Whether you are a beginner or a seasoned grower, learning this process allows you to grow your dahlia collections without starting from scratch each spring. Saving your tubers is a rewarding way to ensure your garden stays colorful for years to come.
Why Saving Dahlia Tubers is Worth the Effort
Dahlias are technically tender perennials. This means they want to live for many years, but they lack the natural "antifreeze" that allows hardy bulbs like tulips or daffodils to survive a deep freeze. If you live in a climate where the ground freezes, leaving them outdoors usually results in the tubers turning to mush.
Saving your tubers is a great way to build a massive garden on a budget. A single tuber planted in May will often grow into a large clump by October. When you dig up that clump, you might find five or ten new tubers that can each become a brand-new plant. It is a bit like a high-interest savings account for your backyard.
Beyond the cost savings, there is a certain pride in "growing on" a specific variety you love. If you had a particular Thomas Edison dahlia that performed perfectly, saving that exact plant ensures you have the same genetics ready to go next season. It turns gardening into a multi-year story rather than a one-season event.
Determining Your Timing
The most common question we hear is: "When is the right time to dig them up?" Timing is the most important part of the process. If you dig too early, the tubers might not be "mature" enough to survive storage. If you wait too long, a deep freeze could damage the crown of the plant.
The First Frost Signal
For most gardeners, the signal to start is the first "killing frost." This is the night when temperatures drop just low enough to turn the dahlia’s lush green foliage into a dark, wilted brown. While it might look a bit sad, this is actually a helpful part of the plant’s life cycle.
When the top of the plant dies back, the energy from the leaves moves down into the tubers. This "curing" process helps the tubers toughen up their skin, which makes them much more likely to stay firm and healthy through the winter months.
The Waiting Period
After that first frost hits, try to wait about a week before you start digging. This gives the tubers time to settle into their dormant state. If you live in a very warm area where frost doesn't happen until December, you can simply wait until the plants look tired and the days are short, usually around mid-November.
Key Takeaway: Wait for the first frost to turn the foliage brown, then give the tubers about 5 to 7 days in the ground to toughen up before you begin digging.
How to Dig Your Dahlia Tubers
Digging dahlias is not difficult, but it does require a bit of gentleness. Dahlia tubers have a "neck" that connects the main body to the stem. This neck is quite fragile, and if it snaps, the tuber usually won't be able to grow next year.
Step 1: Cut Back the Stems
Use a pair of clean loppers or garden snips to cut the main stalks down. You want to leave about 4 to 6 inches of stem sticking out of the ground. Think of this as a "handle" that helps you see where the plant is, though you should never actually use it to pull the plant out of the soil.
Step 2: Loosen the Soil
Using a pitchfork or a large shovel, start digging about 12 inches away from the base of the stem. You want to give the tuber clump plenty of room so you don't accidentally slice through it. Dig a circle all the way around the plant, gently prying upward as you go.
Step 3: Lift with Care
Once the soil is loose, slide your shovel or fork underneath the clump and lift it upward. Use your hands to help support the weight of the soil and the tubers. Gently shake off the largest chunks of dirt. At this stage, the tubers are full of water and are at their most fragile, so handle them like you would a bag of glass ornaments.
Cleaning and Preparing for Storage
Once the tubers are out of the ground, they need a little bit of grooming. Some gardeners prefer to wash their tubers with a garden hose to see the "eyes" more clearly, while others prefer to let the soil dry and just brush it off. Both ways work, provided the tubers end up clean and dry before they go into a box.
Trimming the Excess
Take a look at your clump. You will see the large, fat tubers, but you will also see many thin, hair-like roots. Use your snips to trim away these tiny roots. They don't help the plant during dormancy and can sometimes lead to mold if they stay damp.
You should also check for any damaged or "squishy" tubers. If a tuber was sliced by the shovel or looks like it is starting to rot, it is best to remove it now. A single rotting tuber can spread moisture and bacteria to the rest of the healthy clump during the winter.
Drying and Curing
Before you pack them away, the tubers need to be dry to the touch. Find a spot that is out of direct sunlight and protected from rain—a garage, a shed, or a basement works well. Lay the tubers out on a piece of cardboard or a mesh tray.
Let them dry for about 24 to 48 hours. You want the skin to feel dry like a potato, but you don't want the tuber to start shriveling. If the weather is very humid, it might take an extra day.
The Mystery of the "Eye"
If you want your saved tubers to grow next year, they must have an eye. An eye is a small bump or growth point located on the "crown" of the tuber, which is the area where the tuber meets the main stem.
If you have a tuber that has snapped off the clump and has no piece of the crown attached, it will not grow. It might stay firm all winter, but it will never sprout. When we process tubers at Longfield Gardens, we always ensure that every piece has a clear growth point.
Should You Divide Now or Later?
You have two choices: you can store the entire clump as one big unit, or you can cut the clump into individual tubers now.
- Storing the Clump: This is easier for beginners. It takes up more space, but it protects the tubers from drying out too quickly. You can then divide them in the spring when the eyes are much easier to see.
- Dividing in the Fall: This saves space and allows you to fit more varieties into a single box. However, it requires a bit more skill to identify the eyes while the plant is dormant.
Choosing the Right Storage Medium
The goal of winter storage is to keep the tubers in a "Goldilocks" state: not too wet (which causes rot) and not too dry (which causes shriveling). To achieve this, we use a storage medium to regulate moisture.
Popular Storage Materials
- Peat Moss: This is the most common choice. It is naturally slightly acidic, which can help prevent fungal growth, and it holds just enough moisture to keep the tubers plump.
- Vermiculite: This is a mineral that is excellent at regulating moisture. It is very lightweight and clean to work with.
- Wood Shavings: Many gardeners use the bags of pine shavings sold for animal bedding. These are inexpensive and provide great airflow.
- Newspaper or Plastic Wrap: Some gardeners wrap individual tubers in several layers of newspaper or even plastic wrap. This "dry storage" method works well if your storage area has very stable temperatures.
The Storage Container
Use a container that allows for a small amount of air exchange. A cardboard box, a plastic bin with the lid left slightly ajar, or a milk crate lined with newspaper are all excellent options. Avoid airtight containers, as they trap gases and moisture, which almost always leads to rot.
What to Do Next:
- Choose a storage medium like peat moss or pine shavings.
- Find a sturdy box or crate.
- Place a layer of medium at the bottom, add your tubers (not touching if possible), and cover with more medium.
- Label the outside of the box with the variety name.
Finding the Perfect Storage Location
Where you put the box is just as important as how you pack it. Dahlias need a spot that is cool, dark, and frost-free.
The ideal temperature is between 40°F and 50°F. If the temperature stays above 60°F, the tubers may think it is springtime and try to sprout prematurely. If the temperature drops below 32°F, the water inside the tubers will freeze, expanding and destroying the cell walls. This turns the tuber into a black, mushy mess once it thaws.
Great Storage Spots
- An Unheated Basement: Usually the best option for most homeowners.
- A Root Cellar: The traditional choice for keeping vegetables and tubers.
- An Attached Garage: This can work, but be careful that the temperature doesn't drop too low during a cold snap. Keep the box off the concrete floor by placing it on a shelf or a wooden pallet.
Winter Check-ups
Saving dahlia tubers is not a "set it and forget it" task. It is a good idea to check on your boxes about once a month throughout the winter. This simple habit can save your entire collection.
When you check the tubers, look for two things:
- Signs of Rot: If a tuber feels soft, slimy, or has visible mold, remove it immediately. Check the neighboring tubers to make sure they aren't damp.
- Signs of Shriveling: If the tubers look like a wrinkled prune, they are losing too much moisture. You can lightly mist the storage medium (the peat moss or shavings) with a spray bottle of water. Do not soak it; you just want to add a tiny bit of humidity back into the air.
Healthy tubers should remain firm to the touch, much like a fresh potato or a firm apple. If they stay firm until spring, you have been successful!
Preparing for Spring Planting
When the days begin to lengthen in March or April, it is time to wake your tubers up. If you stored them as whole clumps, this is the perfect time to divide them. The eyes will often start to swell and turn pink or white, making them very easy to spot.
Pre-Sprouting (Optional)
If you live in a northern climate with a short growing season, you can give your dahlias a head start by "pre-sprouting" them indoors about 4 to 6 weeks before the last frost. Place the tubers in a shallow tray of damp potting soil and keep them in a warm, bright spot. By the time the soil outside is warm enough to plant, you will already have several inches of green growth.
Moving Outdoors
Wait until all danger of frost has passed and the soil has warmed up to about 60°F before planting your saved tubers in the garden. Planting into cold, wet soil is the most common reason tubers fail to sprout in the spring. Patience is your best friend during the transition from storage to the garden.
Conclusion
Learning how to save dahlia bulbs for next year is one of the most satisfying skills a gardener can acquire. It turns a one-time purchase into a lifelong hobby and allows you to share your favorite varieties with friends and neighbors. While the process requires a few specific steps—digging after the frost, drying carefully, and storing in a cool, dark place—none of it is difficult.
By following these simple guidelines, you can ensure that your favorite dahlias return to brighten your landscape every summer. At Longfield Gardens, we take pride in providing high-quality tubers that are ready to perform, and we love seeing our customers grow those collections year after year.
"Saving tubers is like preserving a piece of last summer's joy to be reopened next spring. With just a little bit of care, your garden can become more beautiful with every passing year."
Ready to grow your collection? Browse our selection of premium dahlia tubers and start planning your most colorful garden yet.
FAQ
Can I leave my dahlia tubers in the ground if I live in a warm climate?
If you live in USDA Hardiness Zone 8 or warmer, you can often leave your dahlias in the ground over the winter. To help them survive, cut the stems back and apply a thick layer of mulch, such as straw or wood chips, to protect the crowns from occasional chilly nights. However, if your winters are very wet, digging them up might still be safer to prevent rot.
What should I do if my tubers look a bit shriveled in February?
Shriveling is a sign that the air in your storage area is too dry. You don't need to panic; simply use a spray bottle to lightly mist the storage medium (like the peat moss or shavings) with water. This will increase the humidity around the tubers and help them rehydrate without getting so wet that they rot.
Do I have to wash the dirt off the tubers before storing them?
You do not have to wash them, and many successful gardeners prefer not to. Brushing off the loose soil once it has dried is often enough. Washing can make it easier to see the "eyes" if you plan to divide the tubers in the fall, but you must ensure they are completely dry before packing them away to avoid mold issues.
Is it okay to store dahlias in the refrigerator?
While a refrigerator is cool, it is often too cold and too dry for dahlia tubers. Most refrigerators are kept around 35-38°F, which is very close to the freezing point. Additionally, the low humidity in a fridge can cause tubers to shrivel quickly. A cool basement or garage is generally a much better environment for long-term storage.
