Table of Contents
- Introduction
- Understanding the Right Environment for Dahlias
- Determining Your Zone and Winter Strategy
- How to Overwinter Dahlias in the Ground
- Why Digging Dahlias is Often the Best Choice
- The Best Timing for Digging Tubers
- A Step-by-Step Guide to Digging Dahlias
- Preparing Tubers for Winter Storage
- The Right Storage Environment
- Checking Your Tubers Mid-Winter
- Dividing Your Dahlias: Fall vs. Spring
- Handling Container-Grown Dahlias
- When to Bring Dahlias Out of Storage
- Essential Tips for Success
- Conclusion
- FAQ
Introduction
Few sights in the garden are as rewarding as a dinnerplate dahlias in full bloom. From the massive, intricate petals of dinnerplate varieties to the cheerful, geometric shapes of pompons, these plants offer a spectacular finale to the growing season. Because we want to enjoy these vibrant colors year after year, the question of how to handle them once the weather turns cold is one of the most common topics we discuss at Longfield Gardens.
Whether you need to dig up your dahlia tubers—often called dahlia bulbs by many home gardeners—depends mostly on where you live and your local soil conditions. For a broader look at dahlias, start here. In some regions, these plants can stay tucked into the ground all winter, while in others, they require a bit of indoor care to stay healthy. This guide will help you determine the best approach for your specific garden so you can grow bigger and better dahlias every summer.
Our goal is to make dahlia care simple and approachable for every skill level, and our Planning Guide for Dahlias is a helpful companion. Whether you choose to lift your tubers for the winter or protect them in place with mulch, following a few straightforward steps will ensure your garden remains a source of joy and beauty for seasons to come.
Key Takeaway: Determining if you need to dig up your dahlias depends on your USDA hardiness zone and how much winter moisture your soil holds.
Understanding the Right Environment for Dahlias
To understand why winter care is necessary, it helps to know where dahlias come from. These plants are native to the high-altitude regions of Mexico and Central America. In their natural habitat, they enjoy warm days and cool, dry winters. They have evolved to grow from thick, starchy roots called tubers, which act as a storage tank for energy and moisture.
In the United States, we use USDA hardiness zones to help us decide which plants can survive the winter outdoors. Because dahlias are tropical in origin, they are not naturally equipped to handle deep, penetrating freezes. If the ground freezes solid around the tuber, the water inside the plant cells expands and breaks the cell walls. This usually leads to the tuber becoming soft or mushy when it thaws.
The "Right Plant, Right Place" rule is the best way to approach winter care. If your garden mimics the dahlia’s natural home—warm and relatively dry—they are more likely to survive without much help. If your winters are cold, wet, and snowy, you will need to provide a little extra protection or bring them inside for a few months.
Determining Your Zone and Winter Strategy
The first step in planning for winter is knowing your USDA hardiness zone. This map is based on the average annual minimum winter temperature in your area. You can find your zone easily by searching for your zip code on a Hardiness Zone Map.
Zones 8 and Higher: Leaving Dahlias in the Ground
If you live in USDA Zone 8, 9, or 10, you are in luck. In these warmer climates, the ground rarely freezes deep enough to reach the dahlia tubers. For most gardeners in the southern and western U.S., dahlias can be treated as perennials. You can simply cut the foliage back after it turns brown in late fall and let the tubers rest in the soil until spring.
Zone 7: The Borderline Choice
Zone 7 is the "middle ground" of dahlia care. In a mild winter with well-draining soil, dahlias can often survive outdoors if they are protected with a thick layer of mulch. However, if your garden tends to stay very wet during the winter or if you experience a particularly long cold snap, the tubers may struggle. Many gardeners in this zone choose to dig up their favorites just to be safe, while others experiment by leaving a few in the ground to see how they perform.
Zones 3 through 6: The Need to Dig
For gardeners in the northern half of the U.S., digging is generally necessary. In these zones, the ground freezes several inches (or even feet) deep. Since dahlia tubers are typically planted only 4 to 6 inches deep, they will freeze and perish without being moved to a frost-free environment. While it takes a little bit of effort in the fall, digging up your tubers allows you to multiply your collection for free, which is a wonderful "easy win" for any gardener.
What to do next:
- Identify your USDA hardiness zone using your zip code.
- Observe your soil drainage; if water puddles and stays for hours after rain, your tubers are at higher risk of rot.
- Decide if you want to experiment with leaving tubers in the ground or play it safe by digging.
How to Overwinter Dahlias in the Ground
If you live in a climate where it is safe to leave your dahlias in the garden, you still want to give them the best possible chance of success. The biggest threat to a dormant tuber isn't just the cold—it is cold combined with moisture. "Drainage" is a term gardeners use to describe how fast water leaves the soil. If your soil is heavy clay and stays soggy, tubers are likely to rot even if it doesn't freeze.
To winterize dahlias in place, wait until the first frost has blackened the foliage. This signal tells the plant to go dormant. Once the stems have turned brown, cut them back so only about 3 or 4 inches of the stalk remains above the ground.
Cover the area with a generous "mulch chimney." Use 4 to 6 inches of straw, wood chips, or shredded leaves. This layer acts like a cozy blanket, keeping the soil temperature stable and preventing the ground from fluctuating between freezing and thawing. Some gardeners even place a piece of burlap or a small tarp over the mulch to help shed excess winter rain.
Why Digging Dahlias is Often the Best Choice
Even if you live in a zone where dahlias could survive the winter, there are several reasons why you might choose to dig them up anyway. It gives you the chance to rearrange your colors and heights every spring, and a color-coordinated dahlia collection can make that refresh even easier.
First, dahlias are incredibly productive. A single tuber planted in May will often grow into a large clump of five to ten tubers by October. If you leave these clumps in the ground year after year, they can become overcrowded. Overcrowded plants often produce smaller flowers and are more prone to mildew because air cannot circulate through the dense foliage. Digging them up allows you to divide the clumps, giving you more plants to fill your garden or share with friends.
Second, digging provides a "fresh start" for your garden design. It gives you the chance to rearrange your colors and heights every spring. Finally, digging is the only way to ensure 100% safety for your prized varieties if an unusually harsh winter arrives.
The Best Timing for Digging Tubers
Timing is everything when it comes to a successful harvest. You want to leave the tubers in the ground for as long as possible so they can store up maximum energy for next year's blooms. For a refresher on tuber structure, see Dahlia Tubers: What You Need to Know.
The ideal time to dig is about one to two weeks after the first "hard frost." A hard frost is when temperatures drop low enough to turn the green leaves into a dark, wilted brown. This period of waiting is helpful because it encourages the tubers to enter a deep dormancy and helps the outer skin "cure" or toughen up. This thicker skin makes the tubers more resistant to shriveling and rot during their winter nap.
If you live in an area that doesn't get a frost until very late in the year, you can simply dig them up in mid-to-late November. By this time, the shorter days and cooler soil will have already signaled the plant to slow down.
A Step-by-Step Guide to Digging Dahlias
Digging up dahlias is a straightforward process that should feel like a rewarding afternoon in the garden. Follow these steps for the best results:
Step 1: Cut Back the Foliage
Use a sharp pair of pruners or loppers to cut the stems down to about 4 inches above the soil line. It is a good idea to leave a little bit of the stem attached so you have a "handle" to hold while you move the tubers around.
Step 2: Loosen the Soil
Dahlia tuber clumps can be surprisingly wide—sometimes 12 to 18 inches across. Use a garden fork rather than a shovel if possible. A fork is less likely to accidentally slice through a tuber. Start digging at least 12 inches away from the main stem. Gently lift the soil all the way around the plant before trying to pull it up.
Step 3: Lift with Care
Once the soil is loose, reach under the clump and lift it upward. Avoid pulling hard on the stem, as the "neck" where the tuber connects to the stem is very delicate. If the neck breaks, the tuber may not be able to grow a new sprout in the spring.
Step 4: Remove Excess Dirt
Gently shake the clump to remove large chunks of soil. You can use a garden hose to wash the rest of the dirt away. Getting the tubers clean makes it much easier to see any signs of damage and helps prevent soil-borne diseases from traveling into your storage area.
Key Takeaway: Always use a garden fork and start your digging well away from the center of the plant to avoid damaging the brittle tubers.
Preparing Tubers for Winter Storage
Once your dahlias are out of the ground and clean, they need a short "curing" period before they are tucked away for the winter. This step is essential for long-term health.
Find a cool, dry place that is protected from frost—a garage, a shed, or a covered porch works well. Lay the tubers out on a piece of cardboard or a mesh screen. Let them dry for 2 to 3 days. This allows any remaining moisture on the surface to evaporate and helps the skin firm up even more.
During this time, it is vital to label your tubers. Use a permanent marker to write the variety name directly on the skin of the tuber, or tie a waterproof tag to the stem. It is very easy to forget which clump is which once they all look like brown potatoes!
The Right Storage Environment
The goal of winter storage is to keep the tubers in a state of suspended animation. You want it to be cool enough that they don't try to grow, but warm enough that they don't freeze. If you'd like a deeper look at storage temperatures, read What Temperature Do Dahlias Need to Grow?.
The Ideal Temperature
The "sweet spot" for dahlia storage is between 40°F and 50°F. If the temperature stays above 60°F, the tubers may think it is spring and start to sprout prematurely. If it drops below 32°F, they will freeze and die. Most unheated basements or crawl spaces stay within this ideal range.
Storage Media
You should never store dahlias "naked" or exposed to the open air, as they will shrivel like a dried-out carrot. Instead, pack them in a medium that holds just a tiny bit of moisture but still allows the tubers to breathe. Excellent choices include:
- Pine shavings: The kind used for pet bedding is inexpensive and works beautifully.
- Vermiculite: This mineral holds moisture well and is very clean.
- Peat moss: A classic choice that provides a soft, acidic environment.
- Dry sand: Good for heavier clumps but can be quite heavy to move.
Packing Method
Place a layer of your chosen storage medium in the bottom of a cardboard box or a plastic bin. Lay the tubers on top, making sure they aren't crowded or touching each other too much. Cover them with more medium and repeat the layers until the box is full. If you use plastic bins, leave the lid slightly cracked or drill small holes in the sides to ensure air can circulate.
What to do next:
- Find a storage spot in your home that stays consistently cool but never freezes.
- Purchase your storage medium (shavings or vermiculite) before you dig so you are ready to go.
- Mark your calendar to check your tubers once a month during the winter.
Checking Your Tubers Mid-Winter
Gardening is a cycle of observation. It is a good idea to check on your stored dahlias about once a month. This small step takes only a few minutes but can save your entire collection.
Open your boxes and feel a few of the tubers.
- If they feel mushy or smell bad: This is a sign of rot. Remove the affected tubers immediately so the rot doesn't spread to the healthy ones.
- If they look shriveled or wrinkled: They are getting too dry. Use a spray bottle to lightly mist the storage medium with water. You don't want it to be wet—just "barely damp" like a wrung-out sponge.
- If they look firm and plump: Everything is going perfectly!
Dividing Your Dahlias: Fall vs. Spring
One of the most exciting parts of dahlia gardening is dividing the clumps. You have two choices for when to do this: right after digging in the fall or just before planting in the spring.
Dividing in the Fall
Some gardeners prefer to divide in the fall because the tubers are cleaner and take up less room in storage. However, it can be harder to see the "eyes" in the fall. The eye is the small bump on the neck of the tuber where the new growth will emerge next year. It looks a bit like the eye on a potato.
Dividing in the Spring
At us, we often recommend waiting until spring for beginners, and How to Divide Dahlia Tubers makes the process easier to follow. As the weather warms up in March and April, the eyes will naturally begin to swell and turn slightly pink or green. This makes it much easier to see exactly where to cut. Whether you divide now or later, always use a clean, sharp knife and ensure each division has at least one healthy tuber and one visible eye.
Handling Container-Grown Dahlias
If you grow your dahlias in pots, the winter care process is even easier, and a container-friendly dahlia collection is a natural fit for next season. You have two great options.
The first option is to treat the pot like a storage container. Once the foliage has died back, cut it off and move the entire pot—soil and all—into a cool, frost-free area like a garage. The soil will act as a natural insulator for the tubers. Don't water the pot at all during the winter; you want the soil to stay dry to prevent rot.
The second option is to tip the pot over, gently remove the clump from the soil, and store it in boxes just like garden-grown dahlias. This is usually the better choice if you need the pots for winter displays or if you want to check the health of the tubers more closely.
When to Bring Dahlias Out of Storage
The wait for spring is always full of anticipation! When the birds start singing and the grass begins to green, you can start thinking about your dahlias again.
Wait until the danger of frost has passed in your area before planting tubers directly into the garden. Dahlias love warm soil. A simple rule of thumb is to plant them around the same time you would plant tomatoes or peppers. If you want a "head start" on the season, you can pot your tubers up indoors about 4 to 6 weeks before the last frost date. If you're planning new orders, our Shipping Information can help you time everything correctly.
We take pride in providing high-quality tubers that are ready to perform. By following these storage steps, you are protecting your investment and ensuring that your garden remains a vibrant, blooming paradise.
Essential Tips for Success
Growing dahlias should be a source of relaxation, not stress. Here are a few final reminders to keep your winterizing process simple:
- Labeling is the key to happiness: You will be so glad you took the time to write names on the tubers when spring arrives.
- Airflow prevents rot: Whether in the ground or in a box, make sure your dahlias aren't sitting in stagnant, soggy conditions.
- Be patient: Don't rush the planting process in spring. Cold, wet soil is the enemy of a dormant tuber.
- Experiment: Gardening is a learning process. If you aren't sure if you can leave dahlias in the ground in your area, try it with one or two and see what happens, or browse a rich, warm-toned dahlia collection when you're ready for a fresh palette.
"Winter care is simply an investment in next year's beauty. Taking a little time in the fall ensures a garden full of color in the summer."
Conclusion
Deciding if you need to dig up your dahlia bulbs is a simple matter of matching the plant's needs to your local climate. For most of the United States, digging and storing these beautiful tubers indoors is the best way to guarantee they return bigger and better every year. It is a rewarding ritual that marks the end of one season and the beginning of planning for the next.
At Longfield Gardens, we want every gardener to feel confident in their ability to grow these spectacular flowers, and you can learn more about our promise on the About Us & Our Guarantee. Whether you are lifting clumps in a snowy northern climate or mulching them in a sunny southern garden, the process is a simple, step-by-step journey toward a more beautiful yard.
- Know your USDA zone to choose the right strategy.
- Wait for the first frost before starting your winterizing.
- Store tubers in a cool, dark place between 40°F and 50°F.
- Divide your clumps in the spring to grow your collection.
Ready to plan for next year? Explore our selection of vibrant dahlia varieties and start dreaming of your most colorful garden yet.
FAQ
What happens if I forget to dig up my dahlias in a cold zone?
If you live in a zone where the ground freezes (Zone 6 or lower) and you leave your dahlias in the ground without significant protection, they will likely freeze and turn to mush. However, if the winter is unusually mild or the tubers are planted near a warm foundation, they might occasionally surprise you and return. It is always safest to dig them up if you want to ensure they survive.
Can I leave dahlias in the ground in Zone 7?
Yes, you can often leave dahlias in the ground in Zone 7, but it is a bit of a gamble. To increase their chances, ensure they are in a spot with excellent drainage and cover the area with at least 5-6 inches of insulating mulch. If your area experiences a "polar vortex" or prolonged freezing temperatures, even mulched tubers may be at risk.
Do I need to wash the dirt off the tubers before storing them?
While some gardeners store their tubers with the soil still attached, washing them is generally recommended. Cleaning the tubers makes it much easier to identify the "eyes" for dividing and allows you to spot any soft spots or rot before you put them away. It also removes soil-borne pests that could potentially damage the tubers during their dormancy.
How do I know if my tubers are still alive in the spring?
Healthy tubers should feel firm to the touch, similar to a fresh potato. If they are slightly wrinkled, they may just need a bit of moisture to plump back up. The most important sign of life is the "eye"—a small, often pink or green bump near the neck of the tuber. If you see a sprout or a swelling eye, your dahlia is ready to grow!