Introduction
There is nothing quite like the late-summer splendor of a dahlia garden. These plants are the heavy lifters of the flower world, producing basketfuls of blooms in every imaginable color and shape. As the season winds down, many gardeners feel a sense of accomplishment and a desire to keep that beauty going for next year. Since dahlias are tropical plants native to Mexico, they cannot survive freezing ground temperatures in most parts of the United States.
The good news is that keeping your favorite varieties from year to year is a rewarding and straightforward process. At Longfield Gardens, we want to help you preserve your investment so you can enjoy even larger, more beautiful displays each summer from our dahlia collections. By following a few simple steps to lift and store your tubers, you can ensure they remain healthy and dormant through the winter months.
This guide will walk you through the entire process, from the first frost to spring planting. We will cover the best timing, the most effective storage materials, and how to create a "Goldilocks" environment where your tubers stay just right. With a little bit of preparation, you can turn a single season of dahlias into a lifetime of color, and browse our spring-planted bulbs for next season.
Understanding the Dahlia Life Cycle
To store dahlias successfully, it helps to understand what the plant is doing as the days get shorter. In late summer and early autumn, dahlias stop focusing on upward growth and start funneling energy into their root systems. These thick, sausage-like roots are called dahlia tubers. They act as a storage tank, holding all the nutrients and moisture the plant needs to survive the winter and sprout again in the spring.
In USDA hardiness zones 8 and warmer, dahlia tubers can often stay in the ground year-round if the soil is well-draining. If you're not sure where you fall, check our Hardiness Zone Map. However, for most of us in colder climates, the ground will freeze deep enough to turn these moisture-rich tubers into mush. This is why we "lift" them—which is just a gardening term for digging them up.
Think of winter storage as a long nap. The goal is to keep the tubers cool enough to stay dormant but warm enough that they don't freeze. We also need to manage moisture so they don't dry out like a raisin or rot from too much dampness. Getting this balance right is the key to a successful spring start.
The Signal: When to Start Digging
Timing is one of the most important parts of storing dahlias. If you dig them too early, the tubers may be immature and thin, making them more likely to shrivel in storage. If you wait too long, a deep freeze could damage the crown of the plant.
The most common signal to start the process is the first killing frost. You will know it has happened because your vibrant dahlia plants will turn black or dark brown overnight. While it might look a bit sad, this is actually a helpful part of the process. The frost tells the plant that the growing season is over and it is time to go dormant.
If you live in an area where frost comes very late, you can still begin the process in mid-November. By this point, the plants have usually had enough time to develop sturdy tubers. Waiting for that late-season cool-down helps the "skin" of the tuber toughen up, which provides a natural layer of protection during the winter.
Key Takeaway: Wait for a light frost to turn the foliage brown before you begin digging. This ensures the tubers have finished storing the energy they need for next year.
Step 1: Cutting Back the Foliage
Once the foliage has turned brown, it is time to clear away the top growth. Use a clean pair of garden loppers or hand pruners to cut the main stems. You should leave about 4 to 6 inches of the stem protruding from the ground.
This remaining piece of stem serves two purposes. First, it acts as a handle that helps you locate the center of the clump when you start digging. Second, it allows any remaining moisture in the hollow stems to drain out.
After cutting the plants back, many gardeners choose to wait about a week before digging the tubers out of the earth. This short "rest period" in the soil helps the eyes of the dahlia become more visible. The eyes are small bumps located near the top of the tuber where the new sprouts will emerge in the spring. Being able to see them makes dividing the tubers much easier later on.
Step 2: Digging with Care
Dahlia tubers are surprisingly fragile, especially where the tuber attaches to the main stem. This narrow area is called the "neck." If the neck is broken or cracked, the tuber will not be able to sprout, even if the rest of the root looks healthy.
To dig them up safely:
- Use a Garden Fork: A pitchfork is generally better than a shovel because it is less likely to slice through the tubers.
- Give Plenty of Space: Start digging about 12 inches away from the main stem. This ensures you won't accidentally stab the tubers that have grown outward.
- Work in a Circle: Loosen the soil all the way around the plant before you try to lift it.
- Lift from Beneath: Gently pry the clump upward from the bottom. Avoid the temptation to grab the "handle" and pull. Instead, use your hand to support the weight of the clump from underneath as you lift it out of the hole.
Once the clump is out of the ground, gently shake off the loose soil. You will likely see a cluster of tubers that looks a bit like a bunch of sweet potatoes.
Step 3: Cleaning and Curing
There are two schools of thought when it comes to cleaning dahlia tubers. Some gardeners prefer to wash them thoroughly with a garden hose to remove all dirt. This makes it easier to spot "eyes" and see any signs of damage or rot. Other gardeners, especially those with very sandy or loose soil, prefer to simply brush off the dry dirt, believing that the less moisture introduced at this stage, the better.
If you have heavy clay soil, washing is usually necessary. If you do wash them, be sure to turn the clumps upside down so that water doesn't sit inside the hollow stems, which can cause the center of the clump to rot.
After cleaning, the tubers need to "cure." This just means letting them dry out slightly in a protected area. Place them on a tray, a piece of cardboard, or a mesh screen in a cool, dry spot out of direct sunlight. A garage or a shed is perfect. Let them dry for 24 to 48 hours. For a fuller walkthrough, see How to Lift and Store Dahlia Bulbs. The goal is for the exterior to feel dry to the touch, but you don't want the tubers to start shriveling.
Step 4: To Divide or Not to Divide?
One of the most common questions we get at Longfield Gardens is whether you should divide the dahlia clumps in the fall or wait until the spring. The answer is that both methods work, and the best choice depends on your schedule and storage space.
Dividing in the Fall
Many experienced gardeners prefer to divide their tubers in the autumn. At this time, the tubers are soft and easy to cut. Dividing now also saves a significant amount of storage space, as you are only keeping individual tubers rather than large, bulky clumps.
If you divide in the fall, remember that each individual tuber must have a piece of the "crown" (the area where the tuber meets the stem) and at least one "eye." A tuber without an eye is like an egg without a yolk—it simply won't grow. After cutting, let the raw edges dry for another day to "callous" over before packing them away.
Waiting Until Spring
If you are new to dahlias, waiting until spring is often the safest bet. By springtime, the eyes will be much more prominent and may even be starting to sprout, making it very obvious where to make your cuts. Storing the whole clump can also help protect the individual tubers from drying out too much. The only downside is that the clumps take up more room and the stems will be much tougher to cut through after months of storage.
What to do next:
- Label every clump or tuber immediately using a waterproof marker or garden tag.
- Discard any tubers that feel mushy or show obvious signs of rot.
- Trim off any "rat tails"—the thin, hairy roots at the ends of the tubers.
- Check that your storage containers (bins, boxes, or bags) are clean and ready.
Step 5: Selecting a Storage Medium
You cannot simply toss dahlia tubers onto a shelf and expect them to survive. They need to be tucked into a storage medium that regulates moisture. The goal is to provide an environment that is slightly humid but not wet.
Here are the most popular options:
- Vermiculite: This is often considered the gold standard. It is a lightweight mineral that holds a bit of moisture but also allows for excellent airflow.
- Peat Moss: This is a very common and affordable choice. It should be slightly damp (like a wrung-out sponge) but not soaking wet. If it is bone-dry, it can actually suck moisture out of your tubers.
- Wood Shavings: Pine shavings (the kind used for animal bedding) are inexpensive and work well. They provide good insulation.
- Coarse Sand: This is a heavy option, but it is very effective at maintaining a steady temperature and moisture level.
- Plastic Wrap: Some gardeners have success wrapping individual, clean, dry tubers tightly in plastic kitchen wrap. This seals the moisture inside the tuber itself.
Regardless of which medium you choose, the technique is the same. Start with a layer of material in the bottom of a box or plastic bin. Place your tubers or clumps so they aren't touching each other, then cover them completely with more material. If you are using plastic bins, leave the lids slightly cracked or drill a few small holes in the sides to allow for air exchange.
Step 6: Creating the Perfect Winter Home
The location where you store your tubers is just as important as how you pack them. Dahlias are looking for a "basement feel"—cool, dark, and still.
The ideal temperature range is between 40°F and 50°F. If the temperature drops below freezing (32°F), the water inside the tubers will freeze, expand, and destroy the plant cells. If the temperature stays consistently above 55°F, the tubers may think it is spring and start to sprout prematurely, or they may simply dry out and shrivel.
Common successful storage spots include:
- An unheated (but attached) garage that stays above freezing.
- A cool corner of a basement, away from the furnace or water heater.
- A root cellar or crawl space.
- An insulated garden shed.
If you are worried about the temperature in your storage spot, you can place a simple "min-max" thermometer nearby. This will track the lowest and highest temperatures reached, giving you peace of mind that your dahlias are safe.
Step 7: Monthly Maintenance
One of the biggest mistakes gardeners make is "setting and forgetting" their dahlia tubers. It only takes a few minutes once a month to check on your storage bins, and this simple habit can save your entire collection.
When you check your tubers, look for two things: rot and shriveling.
If you find a tuber that has become soft or smelly, remove it immediately. Rot can spread quickly from one tuber to the next, so getting the "bad apple" out of the bunch is essential. If only a small part of a large clump is rotting, you can often cut the bad part away with a clean knife and put the healthy part back in.
If the tubers look shrivelled or feel like they are becoming "corky," they are losing too much moisture. You can fix this by lightly misting the storage medium with a spray bottle of water. You don't want to make it wet; you just want to increase the humidity slightly so the tubers can rehydrate.
Realistic Expectations for Overwintering
Even the most experienced dahlia growers lose a few tubers over the winter. It is a natural part of gardening. Sometimes a variety is simply a "poor keeper," or an undetected bit of damage from the digging process leads to rot.
Don't let the loss of a few tubers discourage you. If you start the winter with ten tubers and seven or eight make it through to spring, that is a great success! Those survivors will often be larger and more vigorous than they were the year before. If you want to add more proven performers next season, browse our best-selling dahlias.
Remember that weather plays a role, too. An unusually cold winter might mean you need to move your bins further away from an exterior wall, while a warm winter might require you to crack a window in the garage to keep things cool. Staying flexible and observant is the best way to ensure your dahlias return year after year.
Safety and Care
It is important to note that dahlia tubers can be mildly toxic to pets if ingested. If you have curious dogs or cats, make sure your storage bins are tucked away in a place where they cannot be accessed. Similarly, ensure the storage medium you choose (like vermiculite or peat moss) is kept in a closed container to avoid creating dust or a mess in your living space.
Always use clean tools when cutting or dividing your tubers. Wiping your pruners with a quick spray of isopropyl alcohol or a mild bleach solution between different plants helps prevent the spread of any soil-born diseases or viruses. This small step goes a long way in maintaining a healthy garden for years to come. For additional reassurance, our 100% Quality Guarantee backs every order.
Ready for Spring
By the time the birds start singing in March or April, you can pull your bins out of storage. You might see little white or green sprouts starting to peek out from the eyes of your tubers. This is an exciting sign that your winter care has paid off!
If you divided your tubers in the fall, you are ready to plant as soon as the soil warms up. If you kept them in clumps, now is the time to carefully divide them into individual pieces. You can even start them in pots indoors about four weeks before your last frost date to get a "jump" on the season with How to Plant Dahlias.
Conclusion
Storing dahlia tubers for the winter is a simple, satisfying cycle that connects one gardening season to the next. By waiting for the frost, digging with care, and providing a cool, stable home, you can keep your favorite flowers as part of your landscape for many years. It is a process that rewards a little bit of effort with a massive payoff of late-summer color.
At Longfield Gardens, we take pride in providing top-rated dahlias that are ready to perform in your garden. Whether you are adding new varieties to your collection or preserving the ones you already love, we are here to support your gardening journey.
- Wait for the first frost to signal dormancy.
- Cure tubers for 24-48 hours before packing.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly for rot or shrivelling.
The secret to great dahlias isn't just in the planting; it's in the care we give them during their winter rest. Treat your tubers well during the cold months, and they will repay you with a spectacular show of blooms all summer long.
We hope this guide makes you feel confident in protecting your dahlias. If you’re looking to expand your garden next season, we invite you to explore our latest varieties and planning guides to help you create your most beautiful yard yet.
FAQ
Can I leave my dahlia tubers in the ground if I mulch them heavily?
This depends entirely on your USDA hardiness zone. In zones 8 and warmer, a thick layer of mulch (about 4-6 inches) may protect tubers from light freezes. However, in zones 7 and colder, the ground usually freezes deep enough that mulch will not be sufficient to save the tubers, and they should be lifted for the winter.
What should I do if my tubers look shrivelled in January?
Shrivelling is a sign that your storage environment is too dry. To fix this, lightly mist your storage medium (like peat moss or shavings) with water. You want the material to feel slightly damp to the touch, which will allow the tubers to slowly absorb moisture. Be careful not to over-water, as standing water will cause rot.
Is it necessary to wash all the dirt off the tubers before storing?
It is not strictly necessary, but it is highly recommended if you have heavy or wet soil. Cleaning the tubers makes it much easier to inspect them for damage or disease and allows you to see the "eyes" more clearly. If your soil is very sandy and falls off easily, a light brushing is usually enough.
Why did my tubers turn to mush in storage?
Mushy tubers are usually the result of one of two things: freezing or rot. If the storage area dropped below 32°F, the tubers likely froze. If the area was above freezing, the mush is likely rot caused by too much moisture or poor airflow. To prevent this, ensure your storage medium is not soaking wet and that there is a small amount of ventilation in your storage containers.
