Table of Contents
- Introduction
- Understanding When to Dig Your Dahlias
- How to Lift Dahlia Tubers Safely
- Cleaning and Preparing for Storage
- The Importance of Curing
- Should You Divide Your Tubers Now?
- Packing Your Dahlias for a Long Nap
- The Ideal Storage Environment
- Winter Check-ups: The Key to Success
- Realistic Expectations for Overwintering
- Preparing for Spring Replanting
- Conclusion
- FAQ
Introduction
There is nothing quite like the late-summer magic of a dahlia garden in full bloom. From the dinnerplate-sized petals of a Cafe au Lait to the perfectly geometric honeycombs of a ball dahlia, these plants are the undisputed stars of the autumn landscape. While it is easy to think of them as temporary summer guests, the most rewarding part of growing these flowers is realizing you can save that beauty and bring it back year after year.
At Longfield Gardens, we want every gardener to feel confident about keeping their favorite varieties from one season to the next. Even though dahlias are native to the warm climates of Mexico and Central America, they are remarkably resilient if you give them a little help during the cold months. If you live in a region where the ground freezes, overwintering your dahlia tubers is the best way to ensure your garden stays vibrant without having to start from scratch every spring.
This guide will walk you through the simple, reliable process of lifting, cleaning, and storing your dahlia tubers. We will cover the best time to start, how to prepare the tubers for their winter nap, and how to keep them healthy until it is time to plant again. By following these steps, you can turn a single season of color into a lifetime of beautiful bouquets.
Understanding When to Dig Your Dahlias
Timing is everything when it comes to successfully overwintering dahlias. Because these plants are tender perennials, they cannot survive a deep freeze in the soil. However, they actually benefit from a little bit of cold before they go into storage.
In most parts of the United States, the signal to begin the process is the first "killing frost." This is the night when temperatures drop just low enough to turn the dahlia’s lush green foliage to black or dark brown. While it might look a bit sad at first, this is actually a helpful part of the plant's life cycle. This frost tells the plant to stop sending energy to the leaves and flowers and instead pull all those nutrients down into the tubers for the winter.
If you can, try to wait about a week after this first frost before you start digging. This short waiting period allows the tubers to "cure" slightly in the ground, which toughens their skin and makes them less likely to rot or shrivel in storage. If your area doesn't get a hard frost until very late in the year, you should aim to dig them up by mid-to-late November to ensure they aren't trapped in waterlogged or frozen soil.
Key Takeaway: The best time to dig dahlia tubers is about 7 to 14 days after the first hard frost has blackened the foliage. This allows the plant to store maximum energy for next year's growth.
What to do next:
- Monitor your local weather forecast for the first evening temperatures below 32°F.
- Once the foliage turns dark, mark your calendar for one week later to begin digging.
- Ensure you have your labels ready so you don't forget which variety is which.
How to Lift Dahlia Tubers Safely
Lifting dahlia tubers is a straightforward task, but it requires a gentle hand. Unlike potatoes, which are quite rugged, dahlia tubers are attached to a central "neck" that is somewhat brittle. If this neck snaps, the tuber may not be able to sprout the following year.
Start by cutting the stalks down. Use a sharp pair of bypass pruners or a garden saw to cut the main stems about 4 to 6 inches above the soil line. These short "handles" of stem are very helpful for identifying the center of the plant, but you should avoid using them to yank the plant out of the ground.
When you are ready to dig, use a garden fork rather than a shovel if possible. A fork is less likely to slice through a hidden tuber. Begin your digging circle at least 12 inches away from the base of the stem. Dahlias can grow quite wide underground, and you want to avoid "nicking" the outer tubers. Gently pry upward from several angles around the plant until the entire root mass feels loose. Then, carefully lift the whole clump out of the earth.
Tips for Damage-Free Lifting:
- Go Wide: Always start your digging further out than you think you need to.
- Lift, Don't Pull: Use the garden fork to do the heavy lifting rather than pulling on the remaining stems.
- Shake Gently: Once the clump is out, give it a soft shake to remove large chunks of soil, but don't worry about getting it perfectly clean just yet.
Cleaning and Preparing for Storage
Once your dahlias are out of the ground, they need a little bit of grooming before they go into their winter crates. There are two main schools of thought on cleaning: the "wash" method and the "brush" method.
The wash method involves using a garden hose with a gentle spray nozzle to rinse all the soil off the tubers. This makes it very easy to see the eyes (the small bumps where next year's stems will grow) and helps you spot any signs of insect damage or rot. If you choose to wash them, it is vital that you allow them to dry completely afterward.
The brush method is often preferred by gardeners in very humid climates. You simply let the soil dry on the tubers for a few hours and then gently brush it away with your hands or a soft brush. Leaving a tiny bit of soil can sometimes act as a natural protective layer, though it makes it harder to inspect the tubers for problems.
Regardless of how you clean them, you should take a moment to trim off the "mother tuber" if it looks soft or spent. This is the original tuber you planted in the spring. It has done its job and often begins to decay after the growing season. Removing any spindly, hair-like roots will also help keep the main tubers clean and reduce the risk of mold.
Key Takeaway: Clean tubers are easier to inspect for rot, but they must be bone-dry before they are packed away. Any lingering moisture on the surface can lead to fungal issues during the winter.
The Importance of Curing
Curing is perhaps the most overlooked step in keeping dahlia bulbs over winter. Just like onions or garlic, dahlia tubers benefit from a short period of air-drying before they are tucked away. This process allows the outer skin to thicken and "set," which creates a barrier against dehydration and disease.
Find a cool, dry place that is protected from frost—such as a garage, a shed, or a basement. Lay your tubers out in a single layer on top of newspaper, cardboard, or in mesh crates. Avoid placing them in direct sunlight, as this can cause them to shrivel too quickly.
At our trial gardens, we find that 2 to 3 days of curing is usually sufficient. You want the surface to feel dry and the remaining stem pieces to feel less fleshy. If you leave them out for too long (more than a week), they may begin to shrivel. The goal is a tuber that feels firm and plump, like a fresh carrot.
What to do next:
- Place tubers in a well-ventilated area away from freezing drafts.
- Check them daily; they should look "matte" and feel dry to the touch.
- Trim any remaining long stems down to about 1 or 2 inches after the curing process is complete.
Should You Divide Your Tubers Now?
One of the most exciting things about growing dahlias is that one tuber planted in spring often turns into a clump of five to ten tubers by autumn. This means you can multiply your garden for free! The question is: should you divide them in the fall or wait until spring?
For beginners, we often recommend waiting until spring to divide. In the spring, the "eyes" (growth buds) are much easier to see because they begin to swell and turn pink or purple. If you try to divide in the fall, you might accidentally cut off the part of the tuber that contains the eye, rendering that tuber unable to grow.
However, if you have limited storage space, dividing in the fall is a great space-saver. If you decide to divide your tubers now, make sure every individual tuber you cut remains attached to a piece of the "crown" (the area where the tuber meets the main stem). Without a piece of that crown, there will be no eye, and the tuber will not sprout.
Packing Your Dahlias for a Long Nap
The secret to a high success rate is creating a storage environment that mimics the "just right" conditions of a root cellar. You want the tubers to stay dormant, which means they need to be cool, dark, and slightly humid—but never wet.
Choosing a Storage Medium
To keep the tubers from drying out completely, most gardeners pack them in a loose material. Some of the most effective options include:
- Coarse Vermiculite: Excellent for moisture control and very clean.
- Peat Moss: A classic choice that provides a bit of natural acidity to discourage rot.
- Pine Shavings: Often sold as animal bedding, these provide great air circulation.
- Newspaper: If you have a very humid basement, simply wrapping individual tubers in several layers of newspaper can be enough.
Selecting a Container
Cardboard boxes and plastic bins are the most common storage containers. If you use plastic bins, do not snap the lid on tight. Instead, leave it slightly ajar or drill several small holes in the sides to allow for air exchange. If the container is airtight, the tubers will "sweat," and the resulting moisture will quickly lead to rot.
At us, we find that layering is the best approach. Put a few inches of your chosen medium in the bottom of the box, lay the tubers in a single layer so they aren't touching each other, and then cover them with more medium. Repeat this until the box is full.
The Ideal Storage Environment
Once packed, your tubers need a permanent home for the next few months. The ideal temperature range is between 40°F and 50°F.
If the temperature stays consistently above 50°F, the tubers may think it is spring and try to sprout too early. If the temperature drops below 35°F, you risk a sudden cold snap freezing the tubers. A frozen tuber turns into a mushy, black mess that cannot be saved.
Typical storage locations include:
- Unheated Basements: Usually the most consistent environment.
- Attached Garages: Good, but keep the boxes off the concrete floor and away from exterior walls.
- Root Cellars: The gold standard if you are lucky enough to have one.
- Cool Closets: If you live in a warmer zone, a dark closet in the center of the house may be the coolest spot available.
Key Takeaway: Consistency is better than perfection. A steady 50°F is better for the plants than a temperature that swings wildly between 35°F and 60°F.
Winter Check-ups: The Key to Success
Even the most carefully packed dahlia tubers need a little attention during the winter. We recommend checking on your stored tubers once a month. This small effort can save an entire collection.
When you open your boxes, look for two things: rot and shriveling.
If you find a tuber that feels soft, mushy, or smells unpleasant, remove it immediately. Rot can spread quickly to neighboring tubers, so "quarantining" the healthy ones is essential. If only a small part of a tuber is soft, you can sometimes cut that part away with a clean knife and let the cut end air-dry before putting it back.
If the tubers look very wrinkled or feel light and "corky," they are dehydrating. This is common if your storage area is very dry. To fix this, simply use a spray bottle to lightly mist the storage medium (the peat moss or shavings) with a little water. You don't want it to feel wet—just slightly damp, like a wrung-out sponge. This bit of humidity will help the tubers plump back up.
Monthly Maintenance Checklist:
- Gently dig through the medium to feel a few tubers in each box.
- Remove any "bad apples" that show signs of mold or soft spots.
- Mist the packing material if it feels dusty and bone-dry.
- Ensure the storage area hasn't become too warm or too cold due to shifting weather.
Realistic Expectations for Overwintering
While saving dahlias is a wonderful way to grow your garden, it is important to remember that gardening always involves a bit of nature's unpredictability. Even professional growers expect to lose a small percentage of tubers over the winter. Factors like the humidity in your home, the specific variety of dahlia, and even the weather during the previous summer can all play a role in how well they store.
Some varieties are known as "good keepers," while others are a bit more delicate. For example, smaller ball dahlias often have very sturdy tubers that store easily, while some of the giant dinnerplate varieties can be more prone to drying out. Do not be discouraged if a few tubers don't make it to spring. The ones that do survive will often be even more vigorous in their second and third years because they have already acclimated to your local conditions.
Preparing for Spring Replanting
As winter begins to fade and the ground starts to thaw, you will notice the tubers starting to "wake up." You may see small pink buds forming on the crowns. This is an exciting sign that your hard work has paid off!
About 4 to 6 weeks before your last expected frost date, you can bring the boxes into a warmer room to encourage sprouting. If you didn't divide your tubers in the fall, now is the perfect time to do it. The eyes will be very prominent, making it simple to see exactly where to cut.
Wait to plant your tubers outdoors until the soil has warmed to at least 60°F and the danger of frost has completely passed. Planting too early into cold, wet soil can cause the tubers to rot before they have a chance to grow. If you want a head start, you can "pot up" your tubers indoors in early spring and move the established plants into the garden once the weather is settled.
Conclusion
Keeping dahlia bulbs over winter is one of the most satisfying skills a gardener can learn. It transforms the way you look at your garden, turning a seasonal display into a long-term investment in beauty. By following these simple steps—timing your dig with the frost, curing the tubers properly, and providing a cool, dark winter home—you can enjoy your favorite Longfield Gardens varieties for many years to come.
The process of lifting and storing tubers is not just about saving money; it is about the joy of seeing a familiar flower return to your garden, bigger and more beautiful than the year before. As you pack away your premium dahlia tubers this fall, you are already planting the seeds for next year's success.
Final Thought: Successful overwintering is a balance of keeping tubers cool enough to sleep, but protected enough to stay alive. With a little practice, it becomes a simple and rewarding part of your annual garden rhythm.
To get started on your dahlia journey or to find new varieties to add to your collection, we invite you to explore our selection of premium dahlia tubers. There is always room for one more splash of color in the garden!
FAQ
Can I leave my dahlias in the ground all winter if I mulch them?
This depends entirely on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlias in the ground with a thick layer of mulch to protect them. However, in Zone 7 and colder, the ground usually freezes deep enough to kill the tubers, so lifting them is necessary for survival.
Do I have to wash the dirt off the tubers before storing them?
No, washing is not strictly necessary. Many gardeners prefer to simply brush off the loose soil once it has dried. The most important thing is that the dahlia tubers are dry and free of large clumps of wet mud, which can trap moisture and cause rot during the winter months.
What should I do if my dahlia tubers look shriveled in February?
Shriveling is a sign that the storage environment is too dry. You can usually save them by lightly misting the storage medium (like the peat moss or wood shavings) with water. Avoid soaking the tubers directly; you just want to increase the humidity inside the box so they can reabsorb a little moisture.
Why did my dahlia tubers turn to mush in storage?
Mushy tubers are usually caused by one of two things: rot from excess moisture or damage from freezing. Ensure your tubers are completely dry before packing them and that your storage container allows for some air circulation. Also, double-check that your storage area stays consistently above 35°F.
Shipping Information
If you are ordering new dahlias for next year, be sure to review our Shipping Information page so you know when your order will arrive and when to expect planting season to begin.