Introduction
Watching your dahlias reach their peak in late summer is one of gardening’s greatest rewards. At Longfield Gardens, we love how these spectacular blooms provide endless color for bouquets and garden borders. To keep that beauty coming back year after year, many gardeners wonder about the best way to handle the tubers once the season ends. This guide helps you decide if digging your tubers is necessary for your specific location and how to do it with confidence.
Whether you are a seasoned pro or a first-time grower, understanding the life cycle of these plants makes the process feel like a natural part of the season. The decision to dig usually comes down to your local weather and how much you enjoy the ritual of winter preparation. Ultimately, the choice to dig your dahlia tubers depends on your hardiness zone and your goals for next year’s garden.
Understanding Dahlia Hardiness and Your Climate
Dahlias are native to the warm, high-altitude regions of Mexico and Central America. Because of their tropical origins, they thrive in the sun and warmth of summer but are naturally sensitive to freezing temperatures. In the gardening world, we refer to this as being "tender perennials."
The primary factor in deciding if you need to dig up your tubers is your USDA hardiness zone. Most dahlias are only hardy in zones 8 through 11. In these warmer regions, the ground rarely freezes deep enough to reach the tubers, allowing them to remain in the soil year-round. If you live in zones 3 through 7, the winter frost will likely penetrate the soil and cause the tubers to freeze, which leads to them becoming soft and unable to grow the following spring.
However, climate isn't just about temperature. Soil moisture plays a massive role in tuber survival. Even in a warm zone, if your garden stays very wet during the winter, the tubers may rot before spring arrives. This is why many gardeners in zone 8 still choose to dig their tubers—it gives them total control over the environment and ensures the plants stay dry and healthy.
The Benefits of Digging Up Your Tubers
While it might seem like extra work, digging up your dahlias offers several "easy wins" for your garden’s future. It is a rewarding way to wrap up the growing season and prepare for an even bigger display next year.
First and foremost, digging protects your investment. High-quality dahlia tubers are an asset to your landscape. By lifting them, you remove the risk of losing your favorite varieties to an unusually cold winter or an exceptionally rainy spring. It provides peace of mind knowing your plants are tucked away safely in a controlled environment.
Second, digging allows you to divide your tubers. A single dahlia tuber planted in the spring will often grow into a large clump by autumn. If you leave this clump in the ground for several years, it can become overcrowded. Overcrowding leads to smaller flowers and weaker stems because the plants are competing for the same nutrients. By digging them up, you can separate the clump into several individual tubers, effectively giving you free plants to expand your garden or share with friends.
Finally, lifting tubers gives you a chance to inspect their health. You can see which varieties performed best in your soil and ensure that only the healthiest, most vigorous tubers make it into storage. This selection process leads to a more beautiful and consistent garden over time.
When Is the Right Time to Dig?
Timing is one of the most important parts of successful dahlia care. You want to give the tubers as much time as possible to mature and store energy, but you need to get them out before the ground freezes solid.
In most regions, the best time to dig is right after the first killing frost. You will know this has happened when the lush green foliage of your dahlias turns black or dark brown overnight. While the top of the plant looks finished, the tubers underground are actually finishing their final stage of preparation for dormancy.
Many experienced gardeners wait about a week or two after this first frost before they start digging. This short waiting period allows the tubers to "cure" slightly in the ground, which can toughen their skins and make them more resilient during storage. However, do not wait so long that the ground begins to freeze hard. If you live in an area where winter comes on fast, it is perfectly fine to dig as soon as the foliage has withered.
Key Takeaway: Wait for the first frost to turn the leaves brown. This signal tells the plant to move its energy down into the tubers, giving them the fuel they need to sprout vigorously next spring.
Step-by-Step: How to Safely Dig Dahlia Tubers
Digging up tubers is a straightforward process that rewards a gentle touch. Because dahlia "necks"—the narrow part where the tuber connects to the main stem—are quite fragile, the goal is to lift the entire clump without snapping these connections.
Prepare the Plants
Start by cutting the stalks down to about four to six inches above the soil line. This makes the plants much easier to handle and gives you a "handle" to hold onto as you work. Use sharp, clean pruners or loppers to make clean cuts. We recommend wiping your tools with a simple disinfectant between different plants to keep everything healthy and clean.
Loosen the Soil
The most common mistake is digging too close to the center of the plant. Dahlia clumps can grow surprisingly wide over a single summer. Use a sturdy garden fork or a shovel and begin digging about 12 inches away from the main stem. Insert the tool straight down into the soil and gently pry upward. Work your way in a circle around the plant, loosening the soil on all sides.
Lift the Clump
Once the soil is loose, slide your tool deep under the center of the clump and lift it gently toward the surface. Avoid pulling on the stalks themselves, as this can break the tubers off the crown. Instead, use your hands to support the bottom of the root ball as you lift it out of the ground.
Initial Cleaning
Gently shake the clump to remove large chunks of loose soil. At this stage, the tubers are quite hydrated and their skins are thin, so avoid scrubbing them or using force. If the soil is very sticky or heavy, you can use a dull stick or your fingers to poke away the largest clods of earth.
Cleaning and Curing for Storage
Once the tubers are out of the ground, they need a bit of preparation before they go into their winter home. Proper cleaning and drying prevent mold and rot, which are the two biggest challenges during the dormant months.
To Wash or Not to Wash?
There are two schools of thought on washing dahlias. Some gardeners prefer to wash them completely clean with a garden hose. This makes it much easier to see the "eyes" (the small bumps where next year’s growth will emerge) if you plan on dividing the tubers right away. It also removes soil-borne pests.
Other gardeners prefer to leave a light coating of dry soil on the tubers, believing it provides a natural protective layer. Both methods work well. If you do choose to wash them, use a gentle spray of water. Avoid high-pressure settings that might tear the skin of the tubers.
The Curing Process
Curing is simply the process of letting the tubers dry out slightly. Place your cleaned clumps in a frost-free, shaded area with good air circulation. A garage, shed, or basement is perfect. Avoid placing them in direct sunlight, as this can cause them to shrivel too quickly.
Let the tubers sit for one to three days. You are looking for the surface to feel dry to the touch and the skin to appear slightly toughened. If you see the tubers starting to wrinkle significantly, they are getting too dry and should be moved into storage immediately.
Trimming the Stems
Before final storage, trim the remaining stems down further, leaving only about an inch or two. This prevents the hollow stems from holding onto moisture, which can lead to crown rot.
Best Practices for Winter Storage
Successful storage is all about finding a "Goldilocks" environment: not too cold, not too warm, not too wet, and not too dry. At Longfield Gardens, we find that keeping things simple usually yields the best results.
The Ideal Temperature
Dahlia tubers stay healthiest when stored at a temperature between 40°F and 50°F. This is cool enough to keep them dormant but warm enough to prevent freezing. A cool basement, a crawl space, or an attached garage that stays above freezing are often the best spots in a typical home.
Choosing a Storage Medium
Storing tubers in a medium helps regulate moisture levels. You want a material that is slightly damp but mostly dry. Popular choices include:
- Coarse Vermiculite: This is a favorite because it holds a tiny bit of moisture but stays very airy.
- Wood Shavings: Common "pine flakes" used for animal bedding are inexpensive and work beautifully.
- Peat Moss: A classic choice, though it can sometimes be a bit dusty to work with.
- Dry Sand: Good for insulation, though very heavy if you have a lot of tubers.
Place a layer of your chosen medium in a container, lay the tubers on top, and cover them completely.
Selecting the Right Container
Use a container that allows for a little bit of air exchange. Cardboard boxes, plastic crates with holes, or even heavy paper bags are excellent choices. If you use plastic bins, leave the lids slightly ajar or drill a few small ventilation holes in the sides. If the container is airtight, moisture will get trapped, and the tubers may rot.
Monthly Check-ins
It is a good habit to check on your tubers once a month during the winter. If you notice any soft spots or signs of rot, remove those tubers immediately so the problem doesn't spread. If the tubers look very shriveled and dry, give the storage medium a very light misting of water to rehydrate the air around them.
What to do next:
- Label your tubers or boxes by variety or color.
- Place your storage containers off the floor to avoid cold drafts.
- Set a reminder on your calendar to check them once a month.
Leaving Dahlias in the Ground: When Can You Skip the Dig?
If you live in a warmer climate or simply want to try a low-maintenance approach, leaving dahlias in the ground is an option in certain conditions. This is the "right plant, right place" principle in action.
In USDA zones 8 and higher, the ground generally stays warm enough that tubers will survive. However, even in these zones, you should take a few steps to increase their chances of success. After the foliage dies back, cut the stems to the ground. Apply a thick layer of mulch—about 4 to 6 inches of straw, wood chips, or shredded leaves—over the top of the planting site. This mulch acts like a blanket, keeping the soil temperature stable and protecting the crown from frost.
If you live in zone 7, leaving dahlias in the ground is more of a gamble, but it can be successful in well-drained soil and sheltered microclimates. The biggest enemy in zone 7 isn't just the cold; it's the wet winter soil. If your garden has heavy clay that stays soggy, digging is almost always a better choice.
If you decide to leave them in, just keep in mind that they may sprout a little later in the spring than tubers that were started indoors. This is perfectly normal as the ground takes time to warm up.
Growing Dahlias as Annuals
Not every gardener has the space or the desire to store tubers over the winter, and that is completely okay. Gardening should be a source of joy, not a stressful list of chores.
Many people choose to treat dahlias as annuals. In this scenario, you plant your tubers in the spring, enjoy the incredible explosion of color all summer long, and then simply compost the plants once the frost hits. This approach allows you to try new varieties every single year without any winter maintenance.
At Longfield Gardens, we believe there is no "wrong" way to enjoy these flowers. If the idea of digging and storing feels overwhelming, treating them as annuals is a fantastic way to enjoy professional-level blooms with minimal effort. You still get months of beauty for the price of a few tubers, which is often less than the cost of a single store-bought bouquet.
Conclusion
Deciding whether to dig up your dahlia tubers is a personal choice based on your climate and gardening style. In colder regions, digging and storing is the best way to ensure your favorite varieties return to dazzle you next summer. In warmer zones, a simple layer of mulch may be all they need to rest safely through the winter. By following these simple steps for lifting, cleaning, and storing, you can take the guesswork out of dahlia care and look forward to even more spectacular blooms next season.
- Check your zone: Dig in zones 3-7; mulch or dig in zone 8+.
- Wait for frost: Let the foliage turn brown before you start your work.
- Be gentle: Use a garden fork and dig wide to keep the tubers intact.
- Store cool and dry: Aim for 40-50°F in a breathable container.
The cycle of the seasons is part of the magic of gardening. Taking a few moments to tuck your dahlias away for the winter is a rewarding way to invest in the beauty of your future garden.
To get started on your next colorful project, browse our collection of premium dahlia tubers at Longfield Gardens and find the perfect varieties for your home.
FAQ
What happens if I don’t dig up my dahlias in a cold climate?
If you live in a region where the ground freezes (Zone 7 or colder) and you leave your tubers in the ground without significant protection, they will likely freeze. When a tuber freezes, its cellular structure breaks down, causing it to turn into a soft, mushy consistency once it thaws. These tubers will rot in the soil and will not grow back in the spring.
How long can dahlia tubers stay in the ground after a frost?
Tubers can safely stay in the ground for about two weeks after the first killing frost. This period can actually be beneficial as it encourages the tubers to enter dormancy and toughens their skin. However, you should aim to dig them up before the first hard freeze, which is when the air temperature stays below freezing for several hours and the soil surface begins to harden.
Can I store dahlia tubers in a garage?
Yes, a garage can be an excellent storage location as long as it stays above freezing. Ideally, you want a spot that remains between 40°F and 50°F. If your garage is uninsulated and temperatures inside drop below 32°F, the tubers may freeze and die. If you use a garage, keep the containers on a shelf or a wooden pallet rather than directly on the cold concrete floor.
Do I need to wash the dirt off before storing?
Washing the dirt off is a matter of preference. Many gardeners prefer to wash them so they can clearly see the "eyes" and check for any signs of rot or insect damage before storage. However, if your soil is sandy and falls away easily, a simple brushing may be enough. The most important factor is making sure the tubers are dry to the touch before they are packed away in their storage medium.
