Introduction
Dahlias are the undisputed stars of the late-summer garden, offering a spectacular finale of color just as other plants begin to fade. Whether you grow massive dinnerplate varieties or charming pompons, the joy of seeing those first buds open is a highlight for every gardener. At Longfield Gardens, we want to help you enjoy those beautiful blooms year after year with our dahlia collections. Since these plants are native to the warm climates of Mexico and Central America, they need a little extra care to survive the winter in cooler regions.
This guide will show you exactly how to prepare dahlia bulbs—properly known as tubers—for their winter rest. We will cover the best time to dig them up, how to clean and cure them, and the most reliable ways to store them until spring. Following these simple steps ensures your favorite varieties return even stronger next season. With the right preparation, overwintering your dahlias is a rewarding process that protects your garden investment. For a related walkthrough, see our How to Overwinter Dahlia Tubers.
Understanding Dahlia Dormancy
Before you reach for your shovel, it is helpful to understand what happens to a dahlia plant as the season ends. In the fall, shorter days and cooler temperatures signal to the plant that it is time to stop blooming and start storing energy. This energy is tucked away in the tubers, which are the thickened, underground parts of the stem that look a bit like potatoes. For a broader primer, All About Dahlias is a helpful companion guide.
For the tubers to be successful next year, they need time to mature. This maturation process happens best when the plant stays in the ground as the weather cools. While it might be tempting to tidy up the garden early, waiting for the right environmental cues ensures your tubers have the starch reserves they need to sprout again in the spring.
Key Takeaway: Patience is your best tool in the fall. Allowing the plant to enter dormancy naturally leads to healthier tubers and more vigorous growth next summer.
When to Start the Winterization Process
The most common question gardeners ask is when to take the tubers out of the ground. In most parts of the United States, the ideal time is right after the first "killing frost." This is a frost that is cold enough to turn the dahlia’s foliage black or dark brown. If you're not sure how your climate compares, our Hardiness Zone Map can help.
While the top of the plant looks finished after a frost, the tubers underground are perfectly safe. In fact, many gardeners like to leave the tubers in the soil for about 5 to 10 days after the foliage dies back. This brief waiting period helps "set" the skin of the tuber, making it tougher and more resistant to rot during storage.
If you live in a region where a hard frost does not occur until very late in the year, you can begin the process in mid-to-late November. The goal is to get the tubers safely tucked away before the ground freezes solid, as frozen tubers will turn to mush and cannot be saved.
Steps for Timing Your Harvest:
- Watch the local weather forecast for the first frost warning.
- Wait for the foliage to turn black or wilt significantly.
- If possible, let the tubers cure in the ground for a week.
- Plan to dig on a dry, sunny day to make the soil easier to handle.
Cutting Back the Foliage
Once the foliage has been hit by frost, the next step is to clear away the top growth. Use a clean pair of bypass pruners or garden shears to cut the stems down. You should leave about 4 to 6 inches of the main stem protruding above the soil line. For more growing basics, 8 Tips for Growing Better Dahlias is a useful refresher.
These short "stubs" serve two important purposes. First, they act as a handle, making it much easier to lift the heavy clumps of tubers without damaging them. Second, they provide a place to attach a label. It is very easy to forget which tuber is which once they are out of the ground, so labeling now is an essential step for an organized garden next spring.
After cutting, dispose of the old foliage. If your plants were healthy, you can add the leaves to your compost pile. However, if you noticed any signs of powdery mildew or pests during the summer, it is better to discard the foliage in the trash to keep your garden clean for next year.
Lifting the Tubers Safely
Dahlia tubers are surprisingly fragile, especially at the "neck," which is the narrow part where the tuber connects to the main stem. If this neck breaks, the tuber may not be able to grow. To keep them safe, you must be gentle during the lifting process. If you're thinking about next year's display, the Dahlia Dinnerplate Cloud Nine Collection is a good place to browse.
Start by clearing away any mulch or debris from around the base of the plant. Use a garden fork or a large shovel and insert it into the soil about 12 inches away from the center of the plant. You want to dig a wide circle to avoid accidentally slicing through the tubers, which can spread out quite far.
Slowly pry upward from all sides of the clump to loosen the soil. Once the soil is loose, you can gently lift the entire root ball out of the ground using the stem stubs as a guide. Do not pull hard on the stems; if the clump feels stuck, loosen the soil a bit more with your fork.
Key Takeaway: Think of digging dahlias as an archaeological dig. Slow, steady movements and a wide berth around the plant will keep the fragile tubers intact.
Cleaning and Rinsing
Once the tubers are out of the ground, you will likely find them covered in a thick layer of soil. While some gardeners prefer to leave the soil on, most find that cleaning them makes it easier to inspect for damage or rot.
Gently shake the clump to remove large clods of dirt. You can then use a garden hose with a low-pressure spray to wash away the remaining soil. Avoid using a high-pressure nozzle, as the skin of the tubers is quite soft and can be easily nicked. For a compact cutting-garden option, browse Dahlia PomPon Burlesca.
As you wash, take a close look at the tubers. If you see any that are broken, mushy, or appear to be rotting, remove them now. Healthy tubers should feel firm, similar to a fresh potato. Cleaning them thoroughly also ensures you aren't bringing garden pests or excess moisture into your storage area.
The Importance of Curing
Curing is a simple but vital step that involves letting the tubers dry out slightly before they go into storage. This helps prevent mold and rot, which are the biggest challenges during the winter months. For dramatic summer color, try Dahlia Decorative Diva.
After washing, find a protected spot to lay the tubers out. An unheated garage, a shed, or a covered porch works perfectly. It is best to turn the clumps upside down so that any water trapped in the hollow stems can drain out.
Let the tubers dry for about 2 to 3 days. They should be kept out of direct sunlight and away from freezing temperatures. You will know they are ready when the skin feels dry to the touch and the exterior soil has turned to a fine dust. Do not let them dry for too long, or they may begin to shrivel.
Action List for Curing:
- Place tubers in a frost-free, shaded area.
- Turn clumps upside down to drain hollow stems.
- Allow 48 to 72 hours of drying time.
- Check for firm texture before moving to the next step.
To Divide or Not to Divide
Many gardeners wonder if they should divide their dahlia clumps in the fall or wait until the spring. Dividing is the process of cutting the large clump into individual tubers to create more plants.
In the fall, the tubers are soft and easy to cut. However, the "eyes"—the small bumps from which new growth emerges—can be very difficult to see. These eyes are located on the "crown" of the tuber, which is the area where the tuber meets the stem. If a tuber does not have an eye, it will never grow a new plant.
If you are a beginner, we often recommend waiting until spring to divide. By March or April, the eyes begin to swell and turn pink, making them much easier to identify. If you choose to store the whole clump, you simply have a larger root system to work with in the spring, which often leads to earlier blooms.
Choosing the Right Storage Container
The goal of winter storage is to keep the tubers in a "Goldilocks" environment: not too wet, not too dry, and just the right temperature. The container you choose plays a big role in maintaining this balance.
Cardboard boxes, paper bags, and plastic crates are all excellent choices because they allow for some air circulation. If you use plastic bins, be sure to keep the lids slightly ajar or drill small holes in the sides to prevent moisture from building up.
Whatever container you choose, avoid overcrowding. Giving the tubers a little space helps prevent the spread of rot if one tuber happens to fail. If you have many different varieties, consider using separate paper bags for each and writing the name of the dahlia clearly on the outside.
Selecting a Packing Medium
You should never store dahlia tubers completely "naked" in a box. They need a packing medium to insulate them and regulate moisture. The right medium acts like a sponge, absorbing excess humidity while preventing the tubers from drying out completely. For a larger planting, the Dahlia Decorative Summer Jewels Mix - Bulk Offer is a smart option.
Some of the most effective materials include:
- Vermiculite: This is a mineral that is excellent at regulating moisture and is very lightweight.
- Peat Moss: A classic choice that is slightly acidic and helps inhibit fungal growth.
- Pine Wood Shavings: Often sold as animal bedding, these provide great airflow and insulation.
- Dry Potting Soil: A simple and accessible option for most gardeners.
Layer the bottom of your container with a few inches of your chosen medium. Place the tubers on top, then cover them completely so no part of the tuber is exposed to the air. This layer of protection is what keeps the tubers plump and healthy until spring.
Finding the Perfect Storage Location
Temperature is the most critical factor for successful overwintering. Dahlia tubers prefer a consistent temperature between 40°F and 50°F. This range is cool enough to keep them dormant but warm enough to prevent freezing.
An unheated basement, a crawl space, or a cool closet in a mudroom are often the best spots. Avoid areas near a furnace or water heater, as these spots are usually too warm and dry, which will cause the tubers to shrivel. Conversely, do not store them in an outdoor shed that might drop below freezing during a cold snap.
If you aren't sure about the temperature of your storage area, a simple indoor/outdoor thermometer can help you monitor the spot for a few days before you move your tubers in. Keeping them in the dark is also helpful, as it reinforces their natural dormancy.
Overwintering Dahlias in the Ground
If you live in USDA hardiness zone 7 or warmer, you may be able to leave your dahlias in the ground through the winter. This is a great "low-effort" way to enjoy dahlias, though it does come with some risks if the winter is unusually wet or cold. If you prefer a coordinated mix, the Dahlia Assorted Evening Elegance Collection is worth a look.
To protect in-ground dahlias, start by cutting the stems back as usual. Then, apply a thick layer of mulch—about 6 to 12 inches—over the entire planting area. You can use straw, shredded leaves, or wood chips. This mulch acts as a blanket, keeping the soil temperature stable.
In some cases, gardeners in zone 7 will also cover the mulched area with a piece of plastic or a tarp to keep the winter rain from soaking the soil. This prevents the tubers from sitting in cold, soggy earth, which is the primary cause of rot. If you have heavy clay soil, however, we still recommend digging and storing your tubers to be safe.
Monitoring Your Tubers During Winter
Your job isn't quite finished once the tubers are in storage. It is a good idea to check on them about once a month. This quick "wellness check" allows you to catch any issues before they become problems.
Open your containers and feel a few of the tubers. If they feel mushy or smell foul, they are rotting. Remove any affected tubers immediately and discard them. If the packing medium feels very damp, leave the container open for a few days to let it dry out.
If the tubers look shriveled or feel very light, they are getting too dry. You can remedy this by lightly misting the packing medium with water. You don't want it to be wet—just slightly damp, like a wrung-out sponge. This small adjustment is often all it takes to keep them in perfect condition until planting time.
Simple Troubleshooting for Winter Storage
Even with the best care, you might encounter a few hiccups. Most issues are related to either too much moisture or too little. If you notice a white, fuzzy growth on the tubers, that is a sign of mold. This usually happens when the tubers weren't dried enough before storage or the storage area is too humid. Wipe off the mold and move the tubers to a slightly drier spot.
If you find that your tubers are consistently shriveling every year, try switching your packing medium. For example, if you used wood shavings, try vermiculite or slightly damp peat moss next time. Every home has a different humidity level, so it may take a season or two to find the perfect combination of container and medium for your specific environment.
Remember that gardening is a learning process. If you lose a few tubers over the winter, do not be discouraged. Most experienced dahlia growers expect a small amount of loss each year. Focus on the ones that stayed healthy and look forward to the beautiful flowers they will produce.
Getting Ready for Spring
As the days begin to lengthen in late winter, you might notice your stored tubers starting to "wake up." You may see small sprouts beginning to grow from the eyes. This is a wonderful sign that your winter preparation was a success!
Wait until the danger of frost has passed and the soil has warmed to at least 60°F before planting them back in the garden. You can also start them in pots indoors about 4 to 6 weeks before the last frost date if you want to get a head start on the blooming season. For planting instructions, see How to Plant and Grow Dahlia Tubers.
Before planting, give each tuber one last firm squeeze. They should still feel solid. If any are completely dried out or hollow, they can be composted. The healthy, plump tubers are now ready to be tucked into the soil, starting the beautiful cycle all over again.
Conclusion
Preparing dahlia bulbs for winter is one of the most satisfying tasks in the gardening calendar. It marks the end of a successful season and the beginning of the next. By following these steps—digging at the right time, cleaning with care, and providing a cool, stable storage environment—you are giving your dahlias the very best chance to thrive.
At Longfield Gardens, we believe that every gardener can master the art of overwintering. It is a simple way to preserve your favorite colors and shapes while gaining a deeper connection to the rhythm of your garden. With a little bit of preparation now, you will be rewarded with an even more spectacular display of blooms next summer. For peace of mind, our 100% Quality Guarantee backs the plants we offer.
Next Steps for Success:
- Mark your calendar for the average first frost date in your area.
- Gather your storage supplies like cardboard boxes and vermiculite early.
- Label your dahlias while they are still in bloom so you know exactly what you are saving.
- Enjoy the peace of mind that comes with knowing your garden is safe for the winter.
FAQ
Can I leave my dahlias in the ground if I live in a cold climate?
In USDA zones 6 and colder, the ground usually freezes deep enough to kill dahlia tubers. While a very mild winter and heavy mulching might occasionally allow them to survive, digging and storing them indoors is the only way to ensure they return. It is much safer to spend a few hours lifting them than to risk losing your favorite plants to a hard freeze.
What happens if I dig my dahlias before the first frost?
You can dig dahlias before the frost, but the tubers may be smaller and less mature. The plant uses the late summer and early fall to send as much energy as possible into the tubers. If you must dig early due to travel or a busy schedule, try to wait as long as possible into the fall so the tubers are as "ripe" as they can be.
Do I need to wash the tubers, or can I just shake off the dirt?
While washing isn't strictly mandatory, it is highly recommended. Soil can hide pests like slugs or insects, and it also holds moisture that can lead to rot in storage. Cleaning the tubers allows you to see the health of the clump and makes it easier to find the eyes when you are ready to divide them.
My dahlia tubers look like shriveled raisins; are they dead?
Not necessarily! A small amount of wrinkling is normal as the tubers lose a little moisture during dormancy. If they still feel somewhat firm when squeezed, they are likely still alive. Try misting your packing medium to rehydrate them. However, if they are so dry that they feel hollow or brittle like a cracker, they have likely perished and will not sprout. If you still have questions, Contact Us.
