Introduction
There is nothing quite like the late-summer beauty of a dahlia garden. For the biggest blooms, browse our dinnerplate dahlias collection.
From the dinnerplate-sized blooms of Café au Lait, you can see why these flowers are the undisputed stars of the autumn landscape.
The perfectly symmetrical petals of Cornel make them even more memorable. As the days grow shorter and the air turns crisp, many gardeners start to wonder about the next step in the journey. Protecting these beautiful plants for the winter is one of the most rewarding parts of the gardening season.
At Longfield Gardens, we want to make sure your favorite varieties return year after year. Understanding the timing of the fall harvest is the most important part of keeping your tubers healthy. Whether you are a beginner or have been growing for years, knowing exactly when to lift your dahlias ensures they stay firm and ready for next spring.
In this guide, we will cover how to read the signs your plants are giving you, why weather plays such a big role, and the simple steps to take once the season ends. This post is for any home gardener looking to protect their investment and enjoy even bigger blooms next summer. Timing the harvest correctly protects the plant’s health and ensures a vibrant garden for years to come.
Understanding the Best Time to Dig Dahlia Tubers
The question of when to dig up dahlia bulbs—which are technically called tubers—is one of the most common inquiries we receive. While it might be tempting to clear out the garden as soon as you start your fall cleanup, dahlias prefer a specific rhythm. They are not like summer annuals that you simply pull and compost. Because they are tender perennials, they have a biological clock that tells them when to store energy for the following year. For a broader overview of dahlia care, see All About Dahlias.
The most reliable signal to look for is the first frost. In most parts of the United States, we wait until a light frost has touched the foliage. You will know it has happened when the vibrant green leaves turn brown or black overnight. This change may look a bit sad at first, but it is actually a helpful part of the plant’s life cycle. It signals the dahlia to stop focusing on flowers and foliage and start focusing on the tubers underground.
If you live in a region where frost comes very late or not at all, you can use the calendar as your guide. Generally, tubers are mature and ready for storage about 120 days after they were planted. For most gardeners, this lands somewhere in October or November. If your plants are still green but the weather is consistently dropping into the 40s, it is perfectly fine to begin the process.
Why Timing Matters for Next Year's Blooms
You might wonder why we don't just dig them up while they are still blooming beautifully in September. The reason lies in how the plant stores its food. During the long, sunny days of summer, the dahlia is busy making energy through its leaves. Much of that energy goes toward creating those spectacular flowers.
As the season winds down and the temperature drops, the plant begins to move its remaining sugars and nutrients down into the tubers. Think of the tubers like a battery being charged. If you dig them up too early, the "battery" isn't fully charged, and the tubers may not have enough energy to survive the winter in storage. They are also more likely to shrivel or dry out if they haven't had time to develop a thicker, protective skin.
Waiting for that first frost or the natural yellowing of the foliage allows the tubers to "cure" slightly while they are still in the ground. This results in a much heartier tuber that can withstand the dry air of a basement or garage for several months.
Key Takeaway: Patience is rewarded. Waiting for the foliage to die back naturally or from a light frost ensures the tubers have packed away enough energy to sprout vigorously next spring.
Regional Differences: Should You Dig or Not?
The decision of when—and if—to dig depends heavily on your local climate. Gardening is a local activity, and your USDA hardiness zone is the best tool for making this choice. If you are unsure which zone you are in, a quick check of the hardiness zone map will give you the answer.
Zones 8 and Warmer
In these warmer climates, dahlia tubers can often stay in the ground all year round. The soil rarely freezes deep enough to reach the tubers. If you live in these areas, your "digging" might just be a "dividing" session every few years to keep the plants from getting too crowded. You can simply cut the stalks down to the ground and apply a thick layer of mulch to protect the crowns from heavy winter rains.
Zones 7 and Colder
For those of us in the cooler parts of the country, digging is a necessary part of the fall routine. If dahlia tubers are left in soil that freezes solid, the water inside the tuber cells will expand and burst the cell walls. This turns the once-firm tuber into a soft, mushy mess that cannot be saved.
Step 1: Preparing Your Dahlias for Lifting
Once the frost has turned your plants brown, or you have reached the end of your growing season, it is time to prepare. Don't reach for the shovel just yet; there are a few simple tasks that make the job much easier.
First, cut the stalks. We recommend using a sharp pair of pruners or loppers to cut the main stem down to about 4 to 6 inches above the soil line. Leaving this short "handle" is very helpful. It gives you something to hold onto when you are lifting the clump, and it helps you identify where the center of the plant is so you don't accidentally hit the tubers with your tools.
Second, check your labels. It is very easy to forget which dahlia was Thomas Edison once the flowers are gone.
It is just as easy to lose track of Kelvin Floodlight once the flowers are gone. While the stems are still in the ground, make sure each plant has a waterproof tag attached to the remaining stalk. We find that using a garden marker or a simple pencil works best, as these don't fade in the sun or rain as easily as some ink pens.
What to do next:
- Wait for the first frost or late October.
- Cut stems to 4-6 inches above the ground.
- Securely label each variety.
- Gather your tools: a garden fork, a hose, and a marking pen.
Step 2: How to Lift the Tubers Without Damage
The most important rule when digging dahlias is to give the plant plenty of space. Dahlia tubers grow outward from the center stalk, often spreading further than you might expect. If you dig too close to the stem, you risk slicing through the tubers or snapping the "neck." The neck is the narrow part that connects the tuber to the main stalk, and it is where the "eyes" (the growing points) are located. A tuber with a broken neck usually won't grow. For more on the basics, see Dahlia Tubers: What You Need to Know.
We recommend using a garden fork rather than a shovel. A fork allows the soil to fall through the tines and is less likely to cut the tubers. Start by inserting your fork into the soil about 12 inches away from the stalk. Gently pry upward, moving in a circle all the way around the plant.
Once the soil is loosened on all sides, you can use the fork to gently lift the entire clump out of the ground. Use your hands to brush away the largest clods of dirt. At this stage, the tubers are quite hydrated and their skins are thin, so handle them with the same care you would use for a tray of eggs.
Step 3: Washing, Cleaning, and Inspecting
After lifting, you have a choice: to wash or not to wash. Some gardeners prefer to leave the soil on the tubers, believing it provides a layer of protection. However, we generally recommend washing them. Removing the soil makes it much easier to see the condition of the tubers and to spot the "eyes" if you plan to divide them.
Use a garden hose with a gentle spray setting to rinse away the dirt. Avoid using high pressure, as this can tear the skin. Once the tubers are clean, take a close look at the clump. You are looking for firm, plump tubers. If you see any that are soft, smelly, or obviously rotting, use a clean knife to trim them away. Removing damaged parts now prevents rot from spreading to the healthy tubers during the winter.
If you find "mother tubers"—the original tuber you planted in the spring—you might notice they look different. They are often larger, darker, and may have a wrinkled or cork-like texture. Some gardeners choose to remove the mother tuber because it is more prone to rot in storage, but it is not strictly necessary if it still feels firm.
Step 4: Curing for Long-Term Success
Curing is a fancy word for letting the tubers dry out and toughen up before they go into their winter containers. This is a vital step. If you put wet tubers into a sealed box, they will likely mold. For a complete walkthrough, see How to Lift and Store Dahlia Bulbs.
After washing, find a spot that is out of direct sunlight but has good air circulation. A garage, a covered porch, or a basement floor works well. Turn the clumps upside down so any water trapped in the hollow stems can drain out. Leaving them upside down for 24 to 48 hours is usually enough to dry the exterior.
The total curing time can range from a few days to a week, depending on the humidity in your area. You want the skin to feel dry and slightly "leathery" to the touch, but you don't want the tuber itself to start shriveling. If they start to look wrinkled like a raisin, they have dried for too long.
Key Takeaway: Drying the tubers upside down for a day or two prevents water from pooling in the stalks, which is the leading cause of crown rot during winter storage.
Dividing in Fall vs. Spring
Once your dahlias are clean and dry, you have to decide when to divide them. Dividing is the process of cutting the large clump into individual tubers to create more plants for next year.
Some gardeners love to divide in the fall. The tubers are softer and easier to cut, and it saves space in storage. However, the "eyes"—the small bumps that will become next year's stems—can be very hard to see in the autumn. They are often no bigger than a pinhead.
If you are a beginner, we recommend waiting until spring to divide. By March or April, the eyes will begin to swell and may even turn slightly pink or green. This makes it much easier to ensure that every piece you cut has a viable growing point. A tuber without an eye will never grow a plant, even if it looks perfectly healthy. If you choose to wait until spring, simply store the entire clump as one piece.
Ideal Storage Conditions and Materials
The goal of winter storage is to keep the tubers in a state of "suspended animation." You want them to stay cool enough that they don't sprout, but warm enough that they don't freeze. You also want to maintain just enough moisture so they don't turn into driftwood, but not so much that they rot.
The Best Temperature
The ideal temperature for storing dahlia tubers is between 40°F and 50°F. For most people, an unheated basement, a crawl space, or an insulated garage is perfect. Avoid keeping them in a standard living area, as the dry heat from your furnace will shrivel them quickly.
Storage Containers and Media
You need a container that allows for a little bit of air movement. Cardboard boxes, plastic bins with holes drilled in the sides, or paper bags are all great choices.
To keep the moisture levels stable, we suggest packing the tubers in a "medium." This acts as a buffer against the air. Popular choices include:
- Coarse Vermiculite: This is many gardeners' favorite. It is clean, lightweight, and does a great job of managing moisture.
- Pine Wood Shavings: Often sold as pet bedding, these are inexpensive and provide good insulation.
- Peat Moss: A classic choice, though it can be a bit dusty to work with.
- Newspaper: Wrapping individual tubers in several layers of dry newspaper is a simple and effective method.
Layer your chosen material in the bottom of the container, place a few tubers (or clumps) inside, and then cover them with more material. Repeat this until the box is full.
Monitoring Your Tubers Through Winter
Storage isn't a "set it and forget it" task. We recommend checking on your tubers once a month. This small effort can save your entire collection.
Open your boxes and feel a few tubers. If they feel extremely dry and shriveled, use a spray bottle to lightly mist the storage medium with water. You don't want it wet—just slightly damp, like a wrung-out sponge.
If you find a tuber that has developed a spot of mold or rot, remove it immediately. One bad tuber can quickly ruin the others in the box. If the rot is small, you can often cut it away with a clean knife and let the healthy portion air dry before putting it back.
Safety and Expectations in the Garden
While dahlia tubers are exciting to handle, it is important to remember that they can be mildly toxic if eaten by pets. If you have curious dogs or cats, make sure to keep your tubers in a secure location during the curing and storage process.
It is also helpful to have realistic expectations. Even the most experienced gardeners lose a few tubers over the winter. Some varieties, like certain ball dahlias, naturally store better than others with thinner skins. If you lose a few to rot or shriveling, don't be discouraged. It is all part of the learning process.
The weather is the biggest variable in gardening. A very wet fall might make your tubers more prone to rot, while an unusually early freeze might catch you off guard. By paying attention to the local forecast and your plants' appearance, you can adjust your timing to give your dahlias the best chance at a long, healthy life.
Conclusion
Digging up dahlia bulbs is a wonderful way to wrap up the gardening season. It provides a moment of reflection on the beauty of the past summer and a sense of anticipation for the one to come. By waiting for the right signals from the frost and taking the time to cure and store your tubers properly, you ensure that your garden will be even more spectacular next year.
Our team at Longfield Gardens is always here to help you succeed. We take pride in providing high-quality tubers and the practical knowledge you need to grow them with confidence. Remember, gardening is a journey of small wins, and mastering the fall harvest is one of the best wins you can have.
- Wait for a light frost to turn the foliage brown before digging.
- Lift carefully with a garden fork to protect the necks and eyes.
- Cure the tubers upside down in a cool, dry place for a few days.
- Store in a cool, frost-free location between 40°F and 50°F.
Key Takeaway: The success of next year's dahlia garden starts the moment the frost hits this year. Proper timing and storage are the keys to a lifelong love affair with these stunning flowers.
Take the next step and prepare your storage space today. When that first frost arrives, you’ll be ready to give your dahlias the winter rest they deserve.
FAQ
Can I dig up my dahlias before the first frost?
Yes, you can dig them up before the frost if your season is ending or if you need to finish your garden chores early. However, try to wait until at least late September or October. This ensures the tubers have had enough time to mature and store the energy they need to survive the winter and sprout again in the spring.
What happens if I leave my dahlias in the ground during a hard freeze?
If the ground freezes several inches deep, the water inside the dahlia tubers will freeze and expand. This causes the cells to rupture, turning the tubers into mush once the ground thaws. In cold climates (Zone 7 and lower), leaving them in the ground without significant protection almost always results in the death of the plant.
Do I need to wash the dirt off the tubers before storing them?
While some gardeners leave the soil on, we recommend washing them. Washing allows you to inspect the tubers for rot or insect damage and makes it much easier to see the "eyes" for dividing. Just be sure to let the tubers dry completely (cure) before placing them into their winter storage containers to prevent mold.
What is the best temperature for winter dahlia storage?
The ideal temperature range is between 40°F and 50°F. This range is cool enough to keep the tubers dormant so they don't start growing too early, but warm enough to prevent them from freezing. A cool basement, an insulated garage, or a root cellar are usually the best locations in a typical home.
