Table of Contents
- Introduction
- Recognizing the Right Time to Dig
- How to Dig Dahlia Tubers Safely
- Cleaning and Preparing for Storage
- To Divide or Not to Divide?
- Choosing Your Storage Medium
- The Ideal Storage Environment
- Mid-Winter Maintenance and Troubleshooting
- Overwintering Dahlias in Warm Climates
- Preparing for Spring Planting
- Common Mistakes to Avoid
- Conclusion
- FAQ
Introduction
There is nothing quite like the late-summer magic of a dahlia garden. From the dinnerplate-sized blooms of decorative varieties to the intricate, geometric petals of pompons, these plants provide a wealth of color just as the rest of the garden begins to fade. Because dahlias are native to the warm climates of Mexico and Central America, they are not naturally equipped to survive freezing temperatures. To enjoy your favorite varieties year after year, learning how to preserve dahlia bulbs for winter is an essential skill for every home gardener.
At Longfield Gardens, we want to help you keep your garden beautiful by ensuring your tubers stay healthy and viable until spring. If you're ordering new plants, our Shipping Information page explains our timing. While the process of digging and storing dahlias might seem like a major task, it is actually quite straightforward once you understand the basic needs of the plant. By following a few simple steps, you can turn a seasonal flower into a long-term investment that grows more impressive with each passing year.
This guide will walk you through the entire process, from the first frost to the final storage spot. We will cover the best timing for digging, how to clean and cure your tubers, and which storage mediums work best for different home environments. This post is for anyone who wants to save their tubers from the winter chill and ensure a vibrant, bloom-filled dahlia garden when the weather warms up again.
With a little bit of patience and the right technique, you can successfully overwinter your dahlias and look forward to big blooms next summer.
Recognizing the Right Time to Dig
Timing is the most important factor when you begin the process of preserving your dahlia tubers. While it might be tempting to start digging as soon as the weather turns chilly, the plants benefit from staying in the ground as long as possible. As the days grow shorter and temperatures drop, dahlia plants begin to shift their energy from producing flowers to strengthening their root systems.
The Signal of the First Frost
In most regions, the signal to begin is the first killing frost. This is a light freeze that turns the dahlia’s lush green foliage into a dark brown or black color. While the top of the plant looks finished, this event actually triggers a final surge of energy into the tubers.
We recommend waiting about 7 to 10 days after this first frost before you start digging. This brief waiting period allows the tubers to "cure" slightly in the soil. During this time, the eyes (the small buds where next year's growth will emerge) become more prominent, and the outer skin of the tuber begins to toughen up. This extra durability makes them much more likely to survive the winter without shriveling.
Watching the Weather
If you live in a climate where a hard freeze—one where the ground itself freezes solid—happens quickly after the first light frost, you may need to move faster. You want to get the tubers out of the ground before the soil temperature drops below 40°F. If the tubers themselves freeze, they will turn to mush and cannot be saved.
Key Takeaway: Wait for the first frost to turn the foliage brown, then give the tubers about a week in the ground to toughen up before you begin digging.
How to Dig Dahlia Tubers Safely
Dahlia tubers are surprisingly delicate, especially the "neck" of the tuber where it connects to the main stem. If this neck is snapped or severely cracked, the tuber will not be able to sprout in the spring. Using a gentle hand and the right tools will make the process much easier.
Step 1: Cutting Back the Stalks
Before you reach for your shovel, use a pair of clean garden pruners to cut the main stalks down. Leave about 4 to 6 inches of the stem protruding from the ground. These "handles" make it much easier to locate the center of the plant and give you something to hold onto as you lift the clump.
Be aware that dahlia stems are often hollow and can hold a significant amount of water. As you cut them, you might see water bubbling out; this is normal. Just be careful not to tug on the stems too hard, as this can damage the fragile tubers underground.
Step 2: Loosening the Soil
Instead of a traditional pointed shovel, we recommend using a garden fork or a pitchfork. A fork is less likely to slice through a tuber than a solid blade.
Start by inserting the fork into the soil about 12 inches away from the main stem. This ensures you are well outside the "reach" of the tubers. Gently pry the soil upward, then move to the opposite side of the plant and repeat. Work your way in a circle around the plant until the entire root mass feels loose.
Step 3: Lifting the Clump
Once the soil is loose, gently slide your fork underneath the root ball and lift it toward the surface. Use your hands to help support the weight of the clump from below. Avoid lifting the plant solely by the stems, as the weight of the soil can cause the tubers to break off.
Once the clump is out of the ground, gently shake off the large chunks of soil. Do not bang the tubers against each other or against a hard surface, as bruising can lead to rot during storage.
What to do next:
- Cut the stalks to 4–6 inches.
- Dig a wide circle (at least 12 inches) around the stem.
- Lift from underneath with a garden fork.
- Gently remove large clumps of loose dirt by hand.
Cleaning and Preparing for Storage
Once your dahlias are out of the ground, they need to be cleaned and dried before they can be tucked away for the winter. This stage is critical for preventing fungal growth and rot.
Washing the Tubers
Some gardeners prefer to simply brush off the dry dirt, but we find that a gentle rinse with a garden hose is very helpful. Removing the soil allows you to inspect the tubers for any signs of damage or pests. It also makes it much easier to see the "eyes" if you plan to divide your tubers in the fall.
Use a low-pressure stream of water to wash away the soil. Avoid using high-pressure nozzles that could strip the skin off the tubers. Once they are clean, turn the clumps upside down (stems facing the ground) for a few hours. This allows any water trapped in the hollow stems to drain out.
Trimming and Inspection
While the tubers are clean, take a moment to trim away any thin, hair-like feeder roots. You should also cut off any tubers that are dangling by a broken neck or appear mushy.
If you notice any brown or soft spots on a healthy-looking tuber, you can use a clean, sharp knife to trim that part away. Some gardeners like to dust the cut ends with a little bit of cinnamon or a garden-grade sulfur powder, which acts as a natural fungicide.
The Curing Phase
Before the tubers go into their storage containers, they must be "cured." This means letting them dry out in a protected area for a few days.
Place your cleaned tubers in a cool, dry place out of direct sunlight—a garage, basement, or a covered porch works well. Let them sit for 2 to 3 days. During this time, the outer skin will dry and slightly thicken, which helps prevent the tuber from losing too much moisture during the long winter months. Do not leave them out for too long, or they will begin to shrivel.
Key Takeaway: Clean tubers with a gentle rinse, drain the hollow stems by turning them upside down, and let them air-dry for a few days to toughen the skin.
To Divide or Not to Divide?
One of the most common questions we receive is whether you should divide your dahlia clumps in the fall or wait until the spring. Both methods have their advantages, and the best choice depends on your schedule and comfort level.
The Case for Fall Division
Dividing in the fall is often easier because the tubers are softer and more pliable. It also takes up much less storage space, as you are storing individual tubers rather than large, bulky clumps. However, the "eyes" (the small bumps that look like eyes on a potato) can be very difficult to see in the fall. If you divide a tuber and it doesn't have an eye, it will never grow a new plant.
The Case for Spring Division
Many gardeners prefer to store the entire clump and wait until spring to divide. By March or April, the eyes will begin to swell and may even start to sprout, making it very obvious where to make your cuts. The clump also provides a bit of a "buffer" against moisture loss. The downside is that the tubers become quite woody and hard over the winter, making them more difficult to cut through in the spring.
If you are a beginner, we suggest storing the whole clump your first year. It is a safer way to ensure you don't accidentally cut off the growing points.
Choosing Your Storage Medium
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 a raisin. To achieve this balance, we use a storage medium to regulate humidity.
Peat Moss or Vermiculite
One of the most reliable methods is to use slightly damp peat moss or vermiculite. Place a layer of the material in the bottom of a cardboard box or a plastic bin, lay the tubers on top (not touching each other), and cover them with more material.
If the peat moss feels bone-dry, give it a very light mist of water. It should feel like a wrung-out sponge—barely damp to the touch. Cardboard boxes are excellent because they allow for some "drainage" of air, meaning the tubers can breathe. If you use plastic bins, do not snap the lid on tight; leave it cracked or drill a few air holes in the sides.
Wood Shavings
Pine or cedar shavings (the kind sold for animal bedding) are another popular choice. They are inexpensive and provide excellent air circulation. Shavings are particularly good if you have a basement that tends to be slightly damp, as they absorb excess moisture from the air.
The Plastic Wrap Method
Some gardeners have great success by wrapping individual, clean, and dry tubers tightly in plastic kitchen wrap. This creates a tiny micro-environment for each tuber. This method is space-efficient, but it requires that the tubers be perfectly clean and properly cured, or they will rot quickly inside the plastic.
What to do next:
- Choose a container like a cardboard box or a ventilated plastic bin.
- Select a packing material (peat moss, wood shavings, or vermiculite).
- Layer the tubers so they aren't touching each other.
- Label each variety clearly with a waterproof marker.
The Ideal Storage Environment
Where you keep your stored dahlias is just as important as how you pack them. The ideal environment is cool, dark, and consistent.
Temperature is Key
The "sweet spot" for dahlia storage is between 40°F and 50°F. If the temperature stays above 50°F, the tubers may think it is springtime and begin to sprout prematurely. If the temperature drops below freezing (32°F), the tubers will die.
Unheated basements, crawl spaces, or insulated garages are usually the best spots. Avoid placing your storage boxes near a furnace, water heater, or on a cold concrete floor that might freeze.
Humidity and Airflow
While we want to prevent shriveling, stagnant air is the enemy of a healthy tuber. If you are storing your dahlias in a basement, try to keep them in an area with a tiny bit of air movement. Checking on your tubers once a month is a great habit. If you see any signs of mold, remove the affected tuber and increase the ventilation in your box.
Mid-Winter Maintenance and Troubleshooting
Preserving dahlia bulbs for winter isn't a "set it and forget it" task. At Longfield Gardens, we recommend a quick inspection every four to six weeks. This simple check-up can save your entire collection from a single bad tuber.
Dealing with Shriveling
If you open your box and notice the tubers are starting to look wrinkled or feel soft and spongy, they are losing too much moisture. You can remedy this by lightly misting the storage medium (the peat moss or shavings) with water. Do not soak the tubers directly; just add enough moisture to the surrounding material to raise the humidity.
Managing Rot
If you find a tuber that is mushy, slimy, or smelling bad, it is starting to rot. This can happen if the tuber was bruised during digging or if the storage medium is too wet. Remove the rotten tuber immediately and throw it away. If the rot has only affected a small tip of a tuber, you can cut it back to healthy white flesh and let it dry before putting it back.
Signs of Pests
Occasionally, mice or other small rodents might find your dahlia stash. If you see signs of chewing, move your containers to a more secure location or use plastic bins with small, mesh-covered ventilation holes.
Key Takeaway: Check your tubers monthly. Mist the packing material if they look shriveled, and remove any mushy tubers immediately to prevent the spread of rot.
Overwintering Dahlias in Warm Climates
If you are lucky enough to live in USDA hardiness zones 8, 9, or 10, you may not need to dig your dahlias at all. In these warmer regions, the ground rarely freezes deep enough to harm the tubers.
In-Ground Protection
Instead of digging, you can simply cut the stalks down to about 2 inches after the first frost. Cover the entire area with a thick layer of mulch—about 4 to 6 inches of straw, wood chips, or shredded leaves. This acts as an insulating blanket.
The biggest risk in warm climates isn't the cold; it's the rain. If your garden has heavy clay soil that stays soggy all winter, the tubers may rot in the ground. If you have poor drainage, we still recommend digging them up or planting them in raised beds where the water can move away from the root zone.
Spring Emergence
For those who leave their dahlias in the ground, remember to pull the mulch away in early spring as the soil begins to warm. This allows the sun to reach the soil and encourages the tubers to wake up. If you need help finding your zone, check our Hardiness Zone Map.
Preparing for Spring Planting
As the days begin to lengthen in late March or April, it’s time to start thinking about the garden again. This is the most exciting part of the process, as you get to see the results of your winter care.
Waking Them Up
About a month before your last expected frost, move your storage containers to a slightly warmer spot (around 60°F). This gentle increase in temperature signals to the tubers that it's time to grow. If you haven't divided your clumps yet, this is the perfect time to do it, as the eyes will be clearly visible.
Checking Viability
A healthy dahlia tuber should feel firm, like a fresh potato. It should have a neck that is intact and a "crown" (the area where the neck meets the old stem) that has at least one visible eye. If a tuber is completely shriveled and feels hollow, or if it is soft and oozing, it won't grow and should be discarded.
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 4 to 6 weeks before the last frost. Use a well-draining potting mix and place them in a sunny window or under grow lights. By the time the soil outside is warm enough to plant, you'll have a healthy, established plant ready to go.
Common Mistakes to Avoid
Gardening is a continuous learning process, and even experienced growers sometimes lose a few tubers over the winter. Leading with the correct approach will help you avoid the most common pitfalls.
- Avoid digging too early: Let the plant finish its season so the tubers are mature and full of stored energy.
- Don't skip the curing: Drying the tubers for a few days is the best way to prevent fungal issues.
- Keep them cool but safe: Ensure your storage spot won't dip below freezing during a surprise cold snap.
- Label clearly: It is very easy to forget which tuber is which. Use a permanent marker to write the variety name directly on the skin of the tuber or attach a sturdy tag.
For more season-long advice, see 8 Tips for Growing Better Dahlias.
Conclusion
Successfully learning how to preserve dahlia bulbs for winter is one of the most rewarding skills you can develop as a gardener. It allows you to save your favorite colors and forms, and because dahlia clumps grow larger each year, you will eventually have extra tubers to share with friends and neighbors. By focusing on the basics—proper timing, gentle digging, thorough drying, and a cool storage spot—you can ensure your dahlias return even stronger next season.
At Longfield Gardens, we believe that gardening should be a source of joy and satisfaction. While the winter months are a time of rest for the garden, the small amount of effort you put into protecting your tubers now will pay off in a spectacular display of blooms next summer.
- Wait for the frost to trigger dormancy before digging.
- Lift tubers gently to protect the fragile necks.
- Cure for 2–3 days in a cool, dry place.
- Store in a breathable container with peat moss or shavings.
- Check monthly for shriveling or rot.
The secret to vibrant summer dahlias starts with a little bit of care in the fall. By protecting your tubers today, you are already planning for a more beautiful tomorrow.
We invite you to explore our selection of premium dahlia tubers and gardening guides to help you plan your most beautiful garden yet.
FAQ
Can I store dahlia tubers in the refrigerator?
While a refrigerator is cool, it is often too cold and too dry for dahlia tubers. Most refrigerators are kept around 35–37°F, which is very close to the freezing point and may damage the tubers. Additionally, the low humidity in a fridge can cause tubers to shrivel quickly. A cool basement or garage is generally a much better option.
What should I do if my tubers have mold on them?
If you see a light dusting of white mold, it usually means the air is too stagnant. Wipe the mold off with a cloth dipped in a weak solution of water and vinegar, let the tuber dry completely, and return it to storage with better ventilation. If the mold is green or black and the tuber is soft, it is likely rotting and should be discarded.
How do I know if my dahlia tuber has an "eye"?
An eye looks like a small, slightly raised bump or a tiny pimple located on the crown of the tuber (the area where the tuber meets the stem). In the fall, they can be very hard to see. If you aren't sure, wait until spring; the eyes will swell and turn pink or green, making them much easier to identify before you plant.
Do I need to wash the tubers before storing them?
Washing isn't strictly mandatory, but it is highly recommended. Soil can harbor fungi and pests that may cause rot during the winter. Rinsing the tubers also allows you to inspect them for damage and see the eyes more clearly. If you choose not to wash them, ensure the soil is completely dry before you pack them away.