Table of Contents
- Introduction
- Knowing When the Time is Right
- Preparing the Plants for Digging
- How to Dig Carefully
- Cleaning and Curing Your Tubers
- Dividing: Should You Do It Now or Later?
- Choosing the Best Storage Medium
- Creating the Ideal Storage Environment
- Mid-Winter Wellness Checks
- Preparing for Spring Planting
- Conclusion
- FAQ
Introduction
There is nothing quite like the sight of a dahlia garden in late summer. These spectacular dahlias with their intricate petals and vibrant colors are the undisputed stars of the autumn landscape. One of the most rewarding parts of growing them is knowing that these beautiful plants can return to your garden year after year.
At Longfield Gardens, we want to help you enjoy that success by making the process of overwintering your tubers as simple and straightforward as possible. While dahlias are tender perennials that cannot survive a freezing winter in the ground in most regions, keeping them safe until spring is a fun and easy project.
This guide will walk you through exactly how to dig, clean, and store your tubers so they stay healthy and ready to bloom again next season. By following a few basic steps, you can build a permanent collection of your favorite varieties.
Knowing When the Time is Right
The first step in a successful winter storage plan is getting the timing right. In the gardening world, we often look to nature for the perfect signal. For dahlias, that signal is usually the first frost of the season.
Dahlias are native to the warm climates of Mexico and Central America. Because of this, they haven't evolved to handle the deep freezes common in the United States. When the first light frost hits your area, you will notice the foliage on your plants turns black or dark brown. While this might look a bit sad at first, it is actually a very helpful sign. It tells the plant that it is time to go dormant and store its energy in the tubers below the soil.
The Benefit of Waiting for Frost
Waiting for that first frost is beneficial because it allows the tubers to reach their maximum size and maturity. Throughout the summer, the plant is focused on producing flowers. As the days grow shorter and the temperatures drop, the plant shifts its focus downward. It begins packing starches and nutrients into the tubers, which act as a "battery" for next year’s growth.
If you live in a region where a hard freeze (where the ground itself freezes solid) happens quickly after the first light frost, you should aim to dig your tubers shortly after the foliage dies back. If your climate stays relatively mild for a few weeks after the first frost, you can leave the tubers in the ground for about 7 to 10 days to help the "eyes" (the small growth points) become more visible.
Regional Considerations
Your local weather and USDA hardiness zone map will dictate your schedule. In northern zones (Zones 3 through 7), digging is a mandatory part of fall garden chores. In warmer southern climates (Zones 8 and higher), dahlias can often stay in the ground all year, provided the soil is well-draining and doesn't stay soggy during the winter. However, even in warm areas, many gardeners choose to dig their tubers every few years to divide them and keep the plants from becoming too crowded.
Key Takeaway: The first "killing frost" is your best indicator that it is time to start the overwintering process. This allows the plant to naturally transition into dormancy.
Preparing the Plants for Digging
Once the foliage has turned dark from the frost, your next task is to prepare the "clump" (the group of tubers) for lifting. This process starts with a pair of clean, sharp loppers or garden pruners.
Cut the main stems of your dahlias back so that only about 4 to 6 inches of the stalk remains above the ground. These short stems will act as convenient handles when you are lifting the tubers out of the soil. They also help you identify where each plant is located so you don't accidentally step on or damage the tubers while working in the garden.
The Importance of Labeling
Before you move a single shovelful of soil, make sure your labels are secure. This is perhaps the most important part of the entire process. Once dahlia tubers are out of the ground, they all look remarkably similar. If you have several varieties—like a creamy Café au Lait—it is impossible to tell them apart just by looking at the brown roots.
The same is true for a bold Thomas Edison—it is impossible to tell them apart just by looking at the brown roots.
Check that each label is tied firmly to the 6-inch stem handle. Many gardeners prefer to use plastic tags and permanent markers that won't fade or rot if they get damp. You can even write the name of the variety directly on the skin of a large, dry tuber later in the process using a soft pencil or garden marker.
How to Dig Carefully
Dishia tubers are surprisingly fragile, especially at the "neck," which is the narrow part where the tuber attaches to the main stem. If the neck is broken or severely cracked, the tuber may not be able to grow in the spring. This is why we recommend a gentle approach.
The Right Tools for the Job
While a standard shovel can work, a garden fork (sometimes called a pitchfork) is the best tool for this job. The tines of a fork are less likely to slice through a tuber than a solid shovel blade.
- Start at a distance: Place your fork in the soil about 12 inches away from the main stem. Dahlias grow outward as well as downward, and you want to avoid hitting the tubers.
- Work in a circle: Gently push the fork into the soil and pry upward slightly. Move around the plant, loosening the soil on all four sides.
- Lift from below: Once the soil is loose, slide the fork deep under the clump. Use one hand to hold the stem handle and the other to lift the fork.
- Shake gently: Lift the clump out of the hole and gently shake it to remove large chunks of soil.
What to do next:
- Clear a flat workspace in a garage or shed.
- Gather your garden fork and a pair of pruners.
- Double-check that every variety is labeled before lifting.
- Move the clumps to your workspace to begin the cleaning phase.
Cleaning and Curing Your Tubers
After digging, your tubers will likely be covered in garden soil. How you clean them depends on your soil type and personal preference.
To Wash or Not to Wash?
If you have sandy soil, you might find that simply brushing the tubers with your hands is enough to get them clean. However, if you have heavy clay soil, the dirt can act like a wet blanket, holding too much moisture against the tuber and potentially leading to rot.
In most cases, a gentle rinse with a garden hose is the best way to see what you are working with. Washing away the soil reveals the "eyes" and allows you to inspect the tubers for any damage or signs of rot. Be careful not to use a high-pressure setting on your hose nozzle, as you don't want to tear the skin.
The Curing Phase
Once the tubers are clean, they need a short period of "curing" before they go into long-term storage. Curing simply means letting the tubers dry out and allowing the skin to toughen up slightly.
Place your cleaned clumps upside down on a tray, a piece of cardboard, or a wooden pallet. Turning them upside down is important because dahlia stems are hollow. By flipping them, any water trapped inside the stem can drain out, preventing the "crown" (the area where the tubers meet the stem) from rotting.
Store them in a cool, shaded area with good air circulation for 2 to 3 days. Do not leave them in direct sunlight or in a spot where they might freeze. The goal is for the surface of the tubers to feel dry and firm to the touch.
Dividing: Should You Do It Now or Later?
One of the most common questions we receive is whether to divide the dahlia clumps in the fall or wait until the spring. At Longfield Gardens, we believe both methods have benefits, and the right choice depends on your comfort level.
Dividing in the Fall
Many gardeners prefer to divide in the fall because the tubers are softer and easier to cut. It also saves space, as individual tubers take up much less room than large clumps.
To divide, you will need a sharp, sterilized knife. Each individual tuber must have a piece of the "crown" attached that contains at least one "eye." The eye is a small bump or bud from which next year’s plant will grow. If a tuber is cut off without an eye, it will never sprout, even if the tuber itself looks healthy.
Dividing in the Spring
If you are a beginner, waiting until spring is often the easier path. By spring, the eyes will have started to swell and may even be slightly green, making them much easier to identify. Additionally, a whole clump is often more resilient during the winter than individual tubers. If you have plenty of storage space, keeping the clumps intact is a very safe way to go.
Choosing the Best Storage Medium
The key to keeping dahlias healthy all winter is maintaining a balance of moisture. You want the tubers to stay hydrated enough that they don't shrivel up like raisins, but dry enough that they don't grow mold or rot. This is where a storage medium comes in.
Popular Storage Materials
We recommend packing your tubers in a material that can regulate humidity. Some of the most successful options include:
- Peat Moss: This is a classic choice. It is naturally slightly acidic and holds moisture well without feeling "wet."
- Vermiculite: This mineral is excellent for aeration and moisture control. It is very clean and easy to handle.
- Wood Shavings: Often sold as pet bedding, these provide great air circulation. Ensure they are not cedar shavings, as the oils can sometimes be too strong for the plants.
- Coarse Sand: This works well but can be very heavy if you are moving large boxes.
The Packing Process
Use a breathable container such as a cardboard box, a plastic bin with holes drilled in the sides, or a wooden crate. Start by placing a 2-inch layer of your chosen medium at the bottom. Lay your tubers (or clumps) on top so they are not touching each other. This ensures that if one tuber happens to develop a problem, it won't easily spread to its neighbors. Cover the layer completely with more medium and repeat the process until the box is full.
Key Takeaway: Using a medium like peat moss or vermiculite creates a "buffer" that protects your tubers from drying out or getting too damp during their winter nap.
Creating the Ideal Storage Environment
Location is everything when it comes to overwintering dahlias. The "Goldilocks" temperature range for dahlia storage is between 40°F and 50°F.
Avoid the Deep Freeze
The most important rule is that the tubers must not freeze. If the water inside the tuber freezes, the cell walls will burst, and the tuber will turn into a mushy, unusable mess when it thaws. This means an unheated garage might be too cold in northern states, while a heated indoor closet might be too warm.
Avoid Excessive Heat
If the storage area is too warm (above 55°F), the tubers may think it is springtime and begin to sprout prematurely. They may also lose moisture too quickly and shrivel.
Ideal locations often include:
- A cool basement (away from the furnace)
- An insulated crawl space
- An attached garage that stays above freezing
- A root cellar
Mid-Winter Wellness Checks
Gardening is a journey of observation, and that doesn't stop just because the plants are in boxes. We recommend checking on your stored tubers once a month during the winter. This simple habit can save your entire collection.
What to Look For
Open your boxes and feel a few tubers.
- If they look shriveled: They are losing too much moisture. Use a spray bottle to lightly mist the storage medium with water. You don't want it to be soaking wet, just slightly damp to the touch.
- If you see soft spots or mold: This is a sign of too much moisture. Remove any affected tubers immediately to prevent the rot from spreading. You may want to leave the lid off the box for a few days to increase air circulation.
Dahlias are living things, and their needs can change depending on how dry or humid your home is during the winter months. A quick check takes only a few minutes but provides great peace of mind.
Preparing for Spring Planting
As the days begin to lengthen in late March or April, you can start thinking about bringing your dahlias back out. This is the perfect time to do your final dividing if you left the clumps whole in the fall.
If you find you need a few new varieties to refresh your garden, spring is the ideal time to browse our Sedona Collection and find new colors and shapes to add to your collection.
For a quick refresher on spring planting, see our How to Plant Dahlias video.
At Longfield Gardens, we always recommend checking the quality of your tubers one last time before planting. A healthy tuber should feel firm, like a fresh potato. If some tubers didn't make it through the winter, don't worry—this is a normal part of the process. Even experienced gardeners lose a few tubers each year due to weather fluctuations.
We stand behind our plants with a 100% quality guarantee, ensuring your new additions arrive in prime condition for the growing season.
If you want to review delivery timing, our Shipping Information page has the latest schedule.
What to do next:
- Set a monthly reminder on your phone to check your tubers.
- Prepare a cool, dark spot in your home for the storage boxes.
- Keep a spray bottle handy in case the tubers need a quick misting.
- Start a list of varieties you’d like to add to your garden next year.
Conclusion
Digging and storing dahlia bulbs for winter is a rewarding cycle that connects you more deeply with your garden. While it requires a bit of effort in the fall, the payoff comes in the form of spectacular, oversized blooms that get better every year as your tuber clumps grow. By keeping your tubers dry, cool, and frost-free, you ensure that your garden will be filled with color and joy come next summer.
- Wait for the first frost to signal dormancy.
- Dig carefully with a fork to protect the fragile necks of the tubers.
- Cure and dry the tubers upside down before packing.
- Store in a cool, dark place (40-50°F) using a medium like peat moss.
Overwintering dahlias is a simple skill that turns a one-season plant into a lifelong garden companion. With a little care, your favorite flowers will return to brighten your yard year after year.
We are here to support your gardening journey every step of the way. If you are ready to expand your dahlia collection or need more practical advice, we invite you to explore our planning guides and Harvest Collection at Longfield Gardens.
For a warm-toned option, the Golden Hour Collection is another beautiful place to start.
FAQ
When is the best time to dig up my dahlia tubers?
You should wait until the first frost has blackened the foliage, which signals the plant to go dormant. In most regions, this happens between late September and early November. If you live in a frost-free area, you can dig them in late autumn once the plants naturally begin to turn yellow or brown and slow their growth.
Can I store dahlia tubers in the refrigerator?
While a refrigerator stays within the ideal temperature range (around 40°F), it is often too dry for long-term dahlia storage. If you choose this method, you must place the tubers in a sealed container or bag with damp peat moss to prevent them from shriveling. However, a cool basement or crawl space is generally more successful for large collections.
What should I do if my tubers look shriveled in mid-winter?
Shriveling is a sign that the storage environment is too dry. If you notice the tubers losing their firmness, lightly mist the storage medium (such as peat moss or wood shavings) with a spray bottle. Avoid soaking them, as excessive water can cause rot; you just want to provide enough humidity to help the tubers stay plump.
Do I have to wash the dirt off the tubers before storing them?
While it isn't strictly mandatory, washing is highly recommended. Cleaning the tubers allows you to inspect them for damage, pests, or rot that could spread during the winter. It also makes it much easier to see the "eyes" if you plan on dividing your clumps. If you choose not to wash them, make sure the soil is completely dry before packing them away.