Introduction
There is nothing quite like the sight of a dahlia garden in full late-summer glory. These plants are the stars of the season, producing dinner-plate-sized blooms and pom-pons in every color imaginable. At Longfield Gardens, we believe that the only thing better than enjoying a dahlia bloom this year is knowing you can enjoy that very same plant again next summer.
Storing dahlia tubers—often called bulbs—is a rewarding way to build your garden collection without starting from scratch each spring. While these tropical beauties cannot survive a freezing winter in most of the United States, the process of tucking them away for the season is simple and satisfying. This guide is designed for home gardeners who want to ensure their favorite dahlia varieties return bigger and better year after year. By following a few basic steps for digging, cleaning, and storing, you can keep your dahlia collection thriving for many seasons to come.
Why Dahlias Need Winter Protection
Dahlias are native to the high plains of Mexico and Central America. In their natural habitat, they enjoy warm days and well-draining soil that never reaches freezing temperatures. Because they are tender perennials, they do not have the natural "antifreeze" that allows hardy bulbs like daffodils or tulips to survive a deep winter freeze.
In USDA hardiness zones 8 and warmer, some gardeners find success leaving their dahlias in the ground with a thick layer of mulch. However, for those of us in zones 3 through 7, the cold soil and moisture of winter will cause the tubers to freeze and turn to mush. Digging them up is the best way to protect your investment.
Think of winter storage as a long, restful nap for your plants. During the summer, the dahlia plant spends its energy creating flowers and foliage. As the days shorten in the fall, the plant shifts its energy downward. It stores starches and nutrients in the tubers to fuel next year's growth. When we store them correctly, we are simply protecting that stored energy until the spring sun warms the soil again.
The Best Time to Dig Your Dahlias
Timing is one of the most important factors in successful dahlia storage. It can be tempting to dig them up as soon as the weather turns chilly, but the plants benefit from staying in the ground as long as possible.
The signal to begin the process is usually the first "killing frost." This is the frost that turns the lush green foliage into a dark brown or black color. While the top of the plant looks dead, the tubers underground are perfectly fine. In fact, many experienced gardeners wait about a week or two after this first frost before they start digging.
This short waiting period serves a practical purpose. It encourages the tubers to enter a deep dormancy and helps the "skin" of the tuber to toughen up. A thicker skin makes the tubers less likely to shrivel or suffer damage during the months of storage. If you live in a region where a hard frost doesn't come until very late, aim to dig your tubers by mid-November. The goal is to get them out of the ground before the soil itself begins to freeze solid.
What to do next: The Frost Watch
- Monitor local weather reports for the first predicted frost in your area.
- Once the foliage turns black, cut the stalks down to about 4 to 6 inches above the soil line.
- Label each plant immediately so you don’t forget which variety is which once they are out of the ground.
How to Dig Dahlia Tubers Safely
Digging up a dahlia clump is a bit like a treasure hunt. Over the summer, that single tuber you planted has multiplied into a large cluster of many tubers. These clumps can be quite heavy and surprisingly wide, so you need to be gentle during the extraction.
We recommend using a garden fork rather than a shovel. A shovel has a solid blade that can easily slice through a tuber if you misjudge the distance. A garden fork allows you to loosen the soil and lift the clump with much less risk of damage.
Start by digging a circle about 12 inches away from the main stem. Push the fork deep into the soil and gently pry upward. Work your way all the way around the plant, loosening the earth as you go. Once the soil is loose, you can reach under the clump with the fork and lift the entire unit out of the ground.
The most critical part of the dahlia is the "neck"—the thin area where the tuber connects to the main stalk. If the neck snaps or is badly creased, the tuber will likely not grow next year. Always lift the clump from underneath rather than pulling it up by the stem. Supporting the weight from the bottom prevents the necks from snapping under the pressure of the clinging soil.
Cleaning and Preparing for Storage
Once your tubers are out of the ground, they need a bit of cleaning before they go into their winter home. There are two main schools of thought on this: washing them with water or dry-brushing them.
To Wash or Not to Wash
Washing your tubers with a gentle stream from a garden hose is a popular choice. It allows you to see the "eyes" (the growth points) more clearly and removes any soil-borne pests or fungi. If you choose to wash them, be very careful not to use high pressure, which can tear the skin.
On the other hand, some gardeners prefer to leave a bit of soil on the tubers. They believe the native soil acts as a natural protective layer. In this case, you would simply let the clumps dry for a few hours and then gently brush off the largest chunks of dirt. Both methods work well, so you can choose the one that fits your schedule and workspace.
The Curing Process
Regardless of how you clean them, all dahlia tubers need to "cure" before they are packed away. Curing is simply a fancy word for letting the tubers air-dry. Place them in a cool, shaded area with good air circulation—like a garage or a covered porch—for one to three days.
Do not leave them in direct sunlight, as this can cause them to shrivel. The goal is to have the outer skin feel dry to the touch and the cut ends of the stems to appear calloused. If the tubers stay too wet when they are packed, they will rot. If they dry out for too long, they will shrivel and lose their vitality. Finding that middle ground is the key to success.
Understanding Dahlia Anatomy
Before you decide whether to divide your tubers or store them whole, it helps to understand what makes a dahlia tuber viable. For a tuber to grow into a plant next year, it must have three things:
- The Body: This is the fat, sausage-like part of the root that holds all the food and energy.
- The Neck: The narrow part that connects the body to the crown. It must be intact and firm.
- The Eye: This is a small bump or "pimple" located on the crown (the area where the neck meets the old stem). This is where the new sprout will emerge.
If a tuber breaks off and doesn't have a piece of the crown with an eye attached, it will never grow, even if the body is large and healthy. It is essentially just a "blind" root. When we work with dahlias at Longfield Gardens, we always look for these three components to ensure a successful growing season.
Dividing Tubers: Fall vs. Spring
One of the most common questions is whether to divide the large clumps into individual tubers in the fall or wait until the spring. Both options have benefits, and the right choice depends on your space and comfort level.
The Benefits of Fall Dividing
If you have a lot of dahlias and limited storage space, dividing in the fall is a great idea. A large clump can take up a lot of room, but individual tubers can be tucked into small boxes or bags. Additionally, the tubers are softer and easier to cut in the autumn.
To divide in the fall, use a clean, sharp pair of garden snips or a knife. Carefully cut the individual tubers away from the main stalk, ensuring that each one has a piece of the crown and a visible eye. This can be tricky for beginners because the eyes are often very small and hard to see in the fall.
The Benefits of Spring Dividing
Many gardeners prefer to store the clumps whole and wait until spring to divide. During the winter, the eyes become much more prominent and begin to swell or even sprout slightly. This makes it much easier to see exactly where to make your cuts.
Whole clumps also tend to resist shriveling better than individual tubers. The extra mass of the clump helps maintain moisture levels. If you are new to dahlias, storing the clumps whole is often the safest and easiest path to success.
Quick Summary: Preparing for the Box
- Dig carefully with a fork to protect the necks.
- Cure the tubers in a cool, dry spot for 24–72 hours.
- Trim the remaining stems down to about an inch.
- Decide whether to divide now (to save space) or in spring (for easier eye identification).
Creating the Ideal Storage Environment
The "secret" to storing dahlias is mimicking the conditions of a cool, dark cave. You want an environment that is cold enough to keep the plants dormant but warm enough that they never freeze.
Temperature and Humidity
The ideal temperature range is between 40°F and 50°F. If the temperature stays above 55°F, the tubers may think it’s spring and start to sprout prematurely. If it drops below 35°F, you run the risk of a cold snap freezing the tubers.
Humidity is the other half of the equation. You want the air to be somewhat humid (around 70% to 80%) so the tubers don't dry out. However, stagnant, wet air is the enemy, as it leads to mold and rot. Basements, unheated crawl spaces, and cool closets are usually better than garages, which can fluctuate too much in temperature.
Choosing a Storage Medium
To help maintain the right moisture balance, most gardeners pack their tubers in a "medium." This material acts as a buffer, absorbing excess moisture if it's too damp and providing a little humidity if it's too dry. Common choices include:
- Pine or Cedar Shavings: These are affordable and smell great. They provide excellent air circulation and are very effective at preventing rot.
- Vermiculite: This is a lightweight mineral that is excellent at regulating moisture. It is a bit more expensive but very reliable.
- Peat Moss: A classic choice that holds moisture well. If you use peat moss, make sure it is just barely damp—not wet.
- Newspaper: Wrapping individual tubers in several layers of newspaper is a simple, low-cost method that works well in naturally humid basements.
The Plastic Wrap Method
A more modern technique involves wrapping individual, cleaned tubers tightly in plastic kitchen wrap (Saran wrap). The idea is that the plastic traps the tuber's own moisture, preventing shriveling. While this method is time-consuming if you have hundreds of dahlias, it is very popular for small collections because you can easily see if a tuber is rotting through the clear plastic.
Step-by-Step Packing Guide
Once your tubers are cured and you have chosen your medium, it is time to pack them away.
- Choose a Container: Cardboard boxes, plastic bins, or milk crates all work. If using plastic bins, do not snap the lid shut tightly; leave it cracked or drill a few small holes in the sides for ventilation.
- Layer the Bottom: Place a 2-inch layer of your chosen medium (shavings, vermiculite, etc.) at the bottom of the container.
- Arrange the Tubers: Lay the tubers or clumps on top of the medium. Try to keep them from touching each other. This ensures that if one tuber happens to rot, the problem won't easily spread to its neighbors.
- Cover and Repeat: Cover the tubers with another layer of medium. You can stack several layers in one box as long as there is medium between each layer.
- Label Everything: It is heartbreaking to open a box in the spring and not know which tubers are the tall purple ones and which are the short yellow ones. Write the variety name on the tuber itself with a soft pencil or a permanent marker, or use sturdy tags.
Monitoring Your Tubers Through Winter
Storing dahlias isn't a "set it and forget it" task. We recommend checking on your tubers once a month during the winter. This five-minute check can save your entire collection.
When you open your boxes, look for two things: rot and shriveling.
Dealing with Rot
If you see a tuber that feels mushy, looks black, or has fuzzy mold growing on it, remove it immediately. Use a clean knife to cut away any affected areas if the rest of the clump looks healthy. Discard the rotted portion in the trash, not the compost pile.
Dealing with Shriveling
If the tubers look wrinkled and feel light or "corky," they are drying out. This is a common issue in modern homes with forced-air heating. The fix is simple: use a spray bottle to lightly mist the storage medium with water. You don't want it to be soaking wet; just a little bit of moisture will help the tubers plump back up.
Key Takeaway: The Winter Check-In A quick monthly inspection allows you to adjust moisture levels and remove any "bad apples" before they ruin the rest of your dahlia harvest.
When Things Don't Go as Planned
Gardening is a living process, and sometimes, despite our best efforts, a few tubers might not make it through the winter. This is a normal part of the experience. Some dahlia varieties are simply "good keepers" while others are more finicky.
If you lose a few tubers to rot, don't be discouraged. It often means the storage area was a bit too damp or the tubers weren't dried long enough before packing. If they shrivel away to nothing, the area was likely too dry. Each winter is a learning opportunity that helps you fine-tune your method for the following year.
At Longfield Gardens, we always suggest starting with a variety of shapes and sizes. You may find that the smaller ball dahlias store differently than the giant "dinnerplate" types.
Preparing for Spring Planting
As the days begin to lengthen in March and April, your dahlias will naturally start to wake up. You might see small green sprouts emerging from the eyes. This is an exciting sign that spring is just around the corner!
About four to six weeks before your last frost date, you can bring the tubers out of storage. This is the perfect time to divide any large clumps you stored whole. If the tubers look a little sleepy, you can place them in a warm, bright spot to encourage the eyes to "wake up."
Some gardeners like to start their dahlias indoors in pots. This gives the plants a head start and leads to earlier flowers in the summer. Simply plant the tubers in a pot with some light potting soil, leaving the crown just at the surface. Keep the soil slightly damp and place the pot in a warm window. By the time the soil outside is warm enough for planting (around 60°F), you will have a sturdy little plant ready to go.
Conclusion
Successfully storing dahlia tubers is one of the most satisfying skills a gardener can master. It allows you to preserve the beauty of your summer garden and gives you a head start on the following season. By waiting for the first frost, digging with care, and providing a cool, stable winter home, you are ensuring that your favorite flowers will return to dazzle you once again.
At Longfield Gardens, our goal is to help you grow a garden that brings you joy year after year. While it takes a little extra effort to tuck your dahlias in for the winter, the reward of seeing those familiar sprouts in the spring is well worth the time.
- Wait for the frost to signal dormancy.
- Dig wide and deep to protect the fragile necks.
- Cure for a few days to set the skin.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly to ensure the perfect moisture balance.
Whatever your favorite variety may be, we look forward to hearing about your success. The simple act of saving a tuber today ensures a more beautiful and vibrant garden tomorrow.
FAQ
Can I store dahlias in a refrigerator?
While a refrigerator provides a consistent cool temperature, it is generally too dry for dahlia storage. Most refrigerators also have a risk of freezing items in the back or near the cooling element, which would kill the tubers. A cool basement or crawl space is a much better choice for maintaining the right humidity.
What if I forgot to label my dahlias?
If your labels get lost or you forgot to add them, you can still store the tubers! You simply won't know the colors or heights until they bloom next year. This can be a fun "mystery garden" surprise. To avoid this next time, try using a permanent marker to write the name directly on the skin of the tuber.
Is it okay if my tubers look a little shriveled in the spring?
Yes, a small amount of wrinkling is normal and usually doesn't harm the plant. As long as the tuber still feels somewhat firm (like a soft carrot) and not like a dry stick, it will likely plump up quickly once it is planted in moist soil. If they are extremely dry, you can soak them in a bucket of room-temperature water for an hour before planting.
Why did my tubers turn to mush in storage?
Mushy tubers are almost always caused by rot, which happens when there is too much moisture and not enough air circulation. This can happen if the tubers weren't dried long enough before packing, or if the storage medium was too wet. Next year, try extending the drying time to three days and ensuring your storage boxes have ventilation holes.
