Introduction
Dahlias are the undisputed stars of the late-summer garden, offering a spectacular finale of color and form just as other flowers begin to fade. Whether you are growing massive dinnerplate varieties or charming pompons, the joy of seeing those first blooms open is a highlight for any gardener. Because these plants are native to the warm climates of Mexico and Central America, they treat our summer sun like a tropical holiday. However, when the frost arrives, these tender perennials need a little help to make it through to next year.
At Longfield Gardens, we want to help you preserve your favorite varieties so you can enjoy them season after season. Saving your dahlia tubers—often called bulbs—is a rewarding way to expand your garden without starting from scratch each spring. It is a simple, rhythmic part of the gardening year that connects the end of one season to the promise of the next.
This guide will walk you through exactly what to do with your dahlia tubers once the weather turns cold. We will cover the best timing for digging, how to clean and cure the tubers, and the most reliable ways to store them so they stay healthy and plump until spring. With a few basic steps, you can ensure your garden is even more beautiful next year.
Determining Your Garden Zone
The first step in planning your dahlia winter care is knowing your USDA hardiness zone. Dahlias are remarkably productive, but they cannot survive in frozen soil. In warmer climates, such as zones 8 through 11, the ground rarely freezes deep enough to harm the tubers. If you live in these areas, you can often leave your dahlias in the ground year-round. You simply cut the stalks back and perhaps add a fresh layer of mulch for extra protection.
For gardeners in zones 3 through 7, the winter brings sustained freezing temperatures that will turn a dahlia tuber into mush. In these regions, digging and storing the tubers indoors is essential. Some gardeners in zone 7 find success leaving tubers in the ground if they have very well-drained soil and apply a thick "blanket" of straw or mulch, but digging remains the safest bet for ensuring your favorite flowers return.
If you are unsure of your zone, you can check a hardiness zone map using your zip code. This helps you understand the timing of your first frost and how much protection your plants will need. Most shipping information from our facility is timed to these zones, ensuring your plants arrive when it is safe to put them in the ground.
Timing Your Harvest
Knowing exactly when to start the digging process is a matter of watching the weather and the plants themselves. You do not want to dig too early, as the tubers do most of their "bulking up" and energy storage during the shorter days of autumn.
The First Frost Signal
The most common signal to begin the winterizing process is the first frost. This is the night when temperatures drop enough to turn the lush green dahlia foliage into a dark, wilted brown. While it might look a bit sad, this is actually a helpful event. The frost tells the plant to stop sending energy to the leaves and flowers and to go into dormancy.
The Curing Period in the Ground
After that first frost hits, try to leave the tubers in the ground for about a week to ten days before digging. This short waiting period allows the "eyes" (the small buds that will become next year's stems) to become more prominent. It also helps the skin of the tuber to toughen up slightly, which makes them more resilient during storage.
If your forecast calls for a hard, deep freeze (temperatures staying well below 28°F for several hours), go ahead and dig them sooner. You want the foliage to die back, but you do not want the soil—and the tubers inside it—to freeze solid.
Preparing to Dig
Before you grab your shovel, take a moment to label your plants. Once the foliage is brown and the stems are cut, it is nearly impossible to tell a Café au Lait dahlia from a Thomas Edison.
Labeling for Success
Use waterproof tags or garden markers to label the base of each plant. You can wrap a piece of survey tape or a plastic tag around the main stem. Write down the variety name and the color. If you have lost the original tag, even a simple description like "Tall Pink Cactus" or "Short Yellow PomPon" will be incredibly helpful when you are planning your garden layout next spring.
Cutting Back the Stalks
Once you are ready to dig, use a pair of sharp loppers or hand pruners to cut the dahlia stalks down. Leave about 4 to 6 inches of stem protruding from the ground. These "handles" make it much easier to locate the center of the tuber clump and give you something to hold onto as you lift them from the soil. Be aware that dahlia stems are hollow and can sometimes hold water; if you see water pooling in the cut stem, you can gently tip the clump after digging to let it drain.
Lifting the Tubers
Digging up dahlia tubers requires a gentle touch. Unlike potatoes, which can be a bit rugged, dahlia tubers are attached to the central "crown" by narrow necks. These necks are brittle, and if they snap, the tuber may not be able to grow next year.
The Best Tools for the Job
A digging fork (also called a pitchfork) is often better than a shovel for this task. The tines of a fork allow you to lift the soil and the tuber clump without accidentally slicing through the roots. If you only have a shovel, just be extra cautious with your placement.
The Lifting Technique
Start by inserting your fork into the soil at least 12 inches away from the main stem. You want to avoid hitting the tubers, which can spread out quite far from the center. Circle the plant, loosening the soil on all sides.
Slowly pry the clump upward from several angles. Once the soil is loose, reach down and lift the entire root ball from underneath. Shaking the clump gently will help remove the bulk of the garden soil. Do not yank on the stems, as this is the most common way to damage the delicate necks of the tubers.
Key Takeaway: Always dig much further out from the stem than you think you need to. Dahlia clumps grow wider as the season progresses, and a wide circle ensures you don't slice through your prize tubers.
Cleaning and Curing
Once the tubers are out of the ground, they need a little bit of cleaning and a short "rest" before they go into long-term storage. For a closer look at tuber structure, see Dahlia Tubers: What You Need to Know.
To Wash or Not to Wash?
There are two schools of thought on washing tubers. Some gardeners prefer to use a garden hose to wash away all the soil. This makes it much easier to see the "eyes" and check for any signs of rot or insect damage.
Other gardeners prefer to leave the soil on, believing it provides a natural protective layer. If your soil is heavy clay, washing is usually best to prevent the clay from hardening into a brick around the tubers. If you have light, sandy soil, a simple shake and a soft brush might be all you need. If you do wash them, be sure to do it gently with a low-pressure spray.
The Curing Process
"Curing" simply means letting the tubers air dry so the outer skin can dry and any small nicks can heal over. Place your cleaned clumps in a frost-free, shaded area with good air circulation. A garage, a shed, or even a covered porch works well.
Lay them out on a screen, a piece of cardboard, or a layer of newspaper. Avoid direct sunlight, which can cause them to shrivel. Let them dry for 2 to 3 days. They should feel dry to the touch, and any remaining soil should crumble away easily.
To Divide or Not to Divide?
One of the most common questions we hear is whether you should divide your dahlia clumps in the fall or wait until the spring. The answer depends on your comfort level and your storage space. For a broader overview, read All About Dahlias.
The Case for Spring Dividing
For most beginners, we recommend waiting until spring to divide. In the spring, the "eyes" of the dahlia—those small bumps located on the crown where the tuber meets the stem—begin to swell and turn pink or green. This makes it very easy to see where the new growth will come from. If you divide in the fall, these eyes are often dormant and very difficult to spot.
The Case for Fall Dividing
If you are short on storage space, dividing in the fall is a great way to save room. A single large clump can take up a lot of space in a box, whereas ten individual tubers can be tucked into a small bag. If you choose to divide now, make sure every piece you keep has a bit of the "crown" (the area of the stem) attached, as that is where the growth buds are located.
Identifying Viable Tubers
Regardless of when you divide, remember the "Three Essentials" for a dahlia tuber:
- The Body: The fat part of the tuber that holds the energy.
- The Neck: The narrow part that connects the body to the crown.
- The Eye: The bud on the crown that will sprout.
If a tuber has a broken neck or no eye, it will not grow. You can safely compost any tubers that are shriveled, mushy, or completely detached from the crown.
Storage Methods and Media
The goal of winter storage is to keep the tubers in a "Goldilocks" state: not so wet that they rot, and not so dry that they shrivel up like raisins.
Choosing a Storage Medium
To maintain the right moisture balance, most gardeners pack their tubers in a "medium." This material acts as a buffer against changes in humidity. Popular choices include:
- Peat Moss: Excellent for holding just enough moisture.
- Vermiculite or Perlite: Very clean and effective at preventing rot.
- Wood Shavings: The kind used for animal bedding is inexpensive and works well.
- Coarse Sand: Good for insulation, though quite heavy.
Packing the Tubers
Choose a container that allows for a small amount of airflow. Cardboard boxes, plastic crates, or paper bags are ideal. If you use plastic storage bins, do not snap the lid on tight; leave it cracked open so the tubers can breathe.
Layer your chosen medium in the bottom of the container, place the tubers in (making sure they aren't touching each other), and cover them completely. This prevents a single rotten tuber from spreading mold to its neighbors.
The Plastic Wrap Method
Some gardeners have success with "Saran wrap" storage. After cleaning and curing, they wrap individual tubers tightly in plastic wrap. This seals in the tuber's own moisture. While this saves space and doesn't require peat moss, it requires very careful cleaning and drying to ensure no mold spores are trapped inside the plastic.
Finding the Perfect Storage Location
Where you put your boxes is just as important as how you pack them. Dahlias need a cool, dark, and consistent environment.
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 start to sprout too early or dry out. If the temperature drops below 32°F, the tubers will freeze and die.
Common Storage Spots
- Unheated Basements: Usually the most reliable spot in older homes.
- Attached Garages: Often stay at the right temperature, but be careful of "hot spots" near a water heater or "cold spots" near the garage door.
- Root Cellars or Crawl Spaces: Naturally cool and humid, which dahlias love.
Avoid storing your tubers in a standard refrigerator if possible. Refrigerators are often too dry, and if you store fruit like apples nearby, the ethylene gas they release can damage the tubers.
What to Do Next:
- Check your storage area with a thermometer before moving your dahlias in.
- Ensure the containers are off the cold floor by placing them on a shelf or a pallet.
- Keep a log or a photo of your labels so you remember what you have in storage.
Winter Monitoring and Maintenance
Dahlia storage is not a "set it and forget it" task. To ensure the highest success rate, you should check on your tubers about once a month throughout the winter.
Checking for Rot
Open your boxes and feel a few tubers. If you find any that are soft, mushy, or smelling foul, remove them immediately. This prevents the rot from spreading. If you see a small amount of surface mold, you can often wipe it off and leave the container open for a day to increase airflow.
Dealing with Shriveling
If the tubers feel light or look wrinkled like a prune, they are losing too much moisture. You can lightly mist the storage medium (the peat moss or shavings) with a spray bottle of water. You don't want it to be wet, just slightly damp to the touch. This will help the tubers rehydrate.
Managing Early Sprouting
If you notice small white sprouts beginning to grow in February or March, don't panic. This is normal as the plants sense the coming spring. Try to keep the storage area as dark as possible to slow them down. If the sprouts get very long, you can gently pinch them off; the tuber will usually push out a second set of eyes once it is planted in warm soil.
Preparing for Spring
As the days get longer and the ground begins to thaw, your dahlia tubers will be ready to start their next lifecycle.
Waking Them Up
About 4 to 6 weeks before your last frost date, you can move your storage boxes to a slightly warmer spot (around 60°F). This "wakes up" the tubers and encourages the eyes to start swelling. If you haven't divided your clumps yet, this is the perfect time to do it, as the eyes will be very easy to see.
Pre-Starting in Pots
If you live in a region with a short growing season, you can give your dahlias a head start by planting them in pots indoors about a month before the last frost. Use a light potting mix and keep them in a sunny window or under grow lights. By the time the soil is warm enough to plant outside, you will have a sturdy little plant ready to go. For extra support tips, see our How to Pinch and Stake Dahlias guide.
Planting Out
Wait until the soil is at least 60°F and all danger of frost has passed before planting your tubers in the garden. Dahlias love sun, well-drained soil, and plenty of room to grow. For more specific planting depths and spacing, we offer detailed guides to help you get your season off to a great start.
Conclusion
Taking care of your dahlia tubers over the winter is a simple practice that pays dividends in beauty. By following the natural cycle of the seasons—waiting for the frost, digging with care, and providing a cool, dark winter home—you preserve the vibrant colors and unique forms that make dahlias so special. It is a rewarding way to "recycle" your garden and see your favorite flowers grow bigger and better every year.
At Longfield Gardens, we take pride in providing high-quality tubers and the support you need to see them thrive. Whether you are a first-time dahlia grower or a long-time enthusiast, the effort you put into winter care ensures that your garden will be a source of joy for years to come.
"Wintering your dahlias isn't just about saving money; it's about the satisfaction of watching a single tuber multiply into a stunning garden over time."
- Wait for the frost to signal dormancy before digging.
- Cure the tubers in a dry, shaded area for a few days.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly for any signs of rot or extreme dryness.
Ready to add more color to your collection? Browse our selection of dahlia tubers at Longfield Gardens and start planning your most beautiful garden yet.
FAQ
Can I leave my dahlia tubers in the ground if I use a lot of mulch?
This depends entirely on your climate. In USDA zones 8 and warmer, a thick layer of mulch is usually enough to protect tubers from the light freezes that occur. In zone 7, it is a gamble that depends on how well your soil drains and how severe the winter becomes. In zones 6 and colder, the ground freezes deep enough that mulch will not provide sufficient protection, and the tubers will likely perish.
My dahlia tubers look shriveled in mid-winter. Are they dead?
Not necessarily! A little bit of wrinkling is normal as tubers lose moisture during dormancy. If they feel firm but look like a prune, they are still viable. Simply mist your storage medium (the peat moss or wood shavings) with a little water to increase the humidity. If the tubers are so dry that they feel hollow or brittle like a cracker, they may have dried out too much to recover.
Do I have to wash the dirt off the tubers before storing them?
You do not have to wash them, but many gardeners find it helpful. Washing allows you to inspect the tubers for pests or rot and makes the "eyes" easier to see. However, if you choose to wash them, you must be very careful to let them dry completely during the curing stage. Storing wet tubers is the fastest way to cause rot. If you have sandy soil, simply brushing off the excess is often sufficient.
What happens if I don't dig up my dahlias in a cold climate?
In regions where the ground freezes (Zone 6 and below), the water inside the dahlia tuber will freeze, expand, and burst the cell walls of the plant. Once the ground thaws, the tuber will turn into a soft, mushy, and often smelly mass. Because dahlias cannot survive these temperatures, you would need to purchase and plant new tubers the following spring to enjoy them again.
