Introduction
There is a unique sense of accomplishment that comes with a successful dahlia season. These spectacular flowers bring unmatched color and drama to the summer garden, often blooming right up until the first frost. While many gardeners treat them as annuals, one of the most rewarding parts of the hobby is saving those favorite varieties to enjoy again next year. If you're planning ahead, browse our dahlia collection.
At Longfield Gardens, we want to help you make the most of your garden investment by showing you how simple the overwintering process can be. If you want a more dramatic look, start with our Dinnerplate Dahlias.
By learning the right techniques for harvesting, you can turn a single plant into a lifelong garden companion. For another classic form, see our Ball Dahlias. Mastering the process of how to dig dahlia tubers ensures your landscape remains vibrant and full of life year after year.
Understanding the Dahlia Lifecycle
Dahlias are tender perennials that grow from underground starch reserves known as tubers. In their native habitats, they stay in the ground all year. However, in most parts of the United States, winter temperatures drop low enough to freeze the soil. Since dahlia tubers are mostly water, a hard freeze will turn them into mush.
If you live in USDA hardiness zones 8 through 11, you may be able to leave your tubers in the ground with a thick layer of mulch. For a quick zone check, use the Hardiness Zone Map. For those of us in zones 3 through 7, digging is a necessary part of the autumn routine. This process allows the plant to go into a dormant state in a protected, frost-free environment.
The goal of digging is not just to save the plant from the cold. It is also an opportunity to see how much the plant has grown. A single tuber planted in the spring will often produce a large clump of five to ten new tubers by autumn. This natural multiplication is one of the most exciting aspects of dahlia gardening.
When Is the Right Time to Dig?
Timing is everything when it comes to harvesting healthy tubers. You want to give the plant as much time as possible to store energy, but you must get them out before the ground freezes solid.
The First Killing Frost
Most gardeners wait for the first "killing frost" to signal the start of the harvest. This is when the foliage turns black or dark brown after a night of freezing temperatures. While the top of the plant looks finished, the tubers underground are perfectly fine. This sudden shock tells the plant to stop growing and start focusing on dormancy.
The 120-Day Rule
If you live in an area where frost comes very late, you don't have to wait for the weather to turn. Dahlias generally need about 120 to 150 days of growth to develop mature, hardy tubers. If your plants have been in the ground for at least four months, they are likely ready to be lifted.
Why Waiting Matters
The longer the tubers stay in the ground, the thicker their "skin" becomes. This curing process happens naturally in the soil and helps the tubers retain moisture during winter storage. If you dig too early, the tubers may be thin-skinned and more prone to shriveling.
Key Takeaway: The ideal time to dig is about one week after the first killing frost. This short wait allows the tubers to "set their eyes," making them easier to identify for future planting.
Essential Tools for the Harvest
Having the right tools on hand makes the job much easier and prevents accidental damage to the fragile tubers. You likely already have most of these items in your garden shed.
- Pruning shears or loppers: Use these to cut through the thick, woody stems.
- A garden fork: This is the preferred tool for lifting. A fork is less likely to slice through a tuber than a solid shovel.
- A shovel: If you have very heavy or rocky soil, a sturdy shovel can help loosen the perimeter.
- Weatherproof tags: Proper labeling is the only way to remember which variety is which.
- A permanent marker: Use a high-quality marker that won't fade or wash off.
- A garden hose: Helpful for rinsing away excess soil if you have heavy clay.
Step-by-Step: How to Dig Dahlia Tubers
Once the foliage has blackened and you have waited a few days for the plant to react, it is time to head into the garden. Follow these steps for a successful harvest.
Step 1: Cut Back the Stems
Start by cutting the main stems of the dahlia plant down to about 4 to 6 inches above the soil level. This remaining stem acts as a "handle" for you to hold onto while lifting, but be careful not to pull on it too hard. Leaving a bit of stem also helps you locate the center of the clump easily. Dispose of the blackened foliage in your compost pile, provided the plant was healthy and free of disease.
Step 2: Loosen the Soil
Tuber clumps can grow much wider than you might expect. For more spacing guidance, see our How Much Space Do Dahlias Need to Grow? Use your garden fork to loosen the soil all the way around the plant. Push the fork deep into the ground and gently pry upward.
Step 3: Lift the Clump
Once the soil is loose on all sides, slide your fork underneath the center of the clump. Lift gently while supporting the weight with your other hand. Do not yank the plant up by the stem. The "neck" of the tuber—the thin part where it connects to the main stalk—is very fragile. If the neck snaps, the tuber will likely not grow next year.
Step 4: Label Immediately
This is perhaps the most important step. It is incredibly easy to mix up varieties once they are out of the ground. Attach a tag to the stem or write the variety name directly on a large tuber with a permanent marker. If you want a compact option for next season, browse our Single Dahlias. At Longfield Gardens, we recommend using a system that stays with the plant from the garden to the storage bin.
What to Do Next:
- Cut stems to 6 inches.
- Dig 12 inches away from the center.
- Lift from underneath with a fork.
- Label the variety right away.
Cleaning and Preparing for Storage
Once the tubers are out of the ground, they need a bit of cleaning before they can be put away for the winter. The amount of cleaning required depends largely on your soil type.
Removing Soil
If you have loose, sandy soil, you can often just shake the clump gently or brush away the dirt with your hands. If you have heavy clay soil, the dirt may be stuck fast. In this case, use a garden hose with a gentle spray setting to wash the tubers. Removing the soil helps you see the condition of the tubers and makes it easier to spot "eyes." If you enjoy spikier blooms, browse our Cactus Dahlias.
The Curing Process
Tubers should be allowed to dry slightly before they go into long-term storage. Place them in a cool, shaded area with good air circulation. A garage or a covered porch works well. Avoid placing them in direct sunlight, as this can cause them to overheat or dry out too fast.
Do not leave tubers out where they might freeze overnight. A single night of frost on an exposed tuber can ruin it. Allow them to dry for 24 to 48 hours until the skin feels firm and the surface moisture is gone. For a broader refresher on winter prep, see our How to Overwinter Dahlias.
Trimming Roots and Stems
Before storage, you can trim away the thin, hair-like feeder roots. These roots do not serve a purpose during dormancy and can sometimes encourage rot if they stay wet. You can also trim the main stem down to about 1 or 2 inches. If the stem is hollow and holds water, turn the clump upside down for a few hours to ensure it drains completely.
Identifying the Anatomy of a Healthy Tuber
To be successful next year, you need to know what makes a tuber viable. Not every piece that comes out of the ground will grow into a new plant. A dahlia tuber needs three specific parts to be successful:
- The Body: This is the fat, potato-like part that stores energy.
- The Neck: The thin part connecting the body to the crown. It must be intact.
- The Crown and Eye: The crown is where the tubers meet the stem. The "eye" is a small bump on the crown that will become next year’s sprout.
If a tuber breaks off and loses its connection to the crown, it will not grow. Even a large, healthy-looking tuber is useless without an eye. This is why we emphasize being gentle during the digging process.
To Divide or Not to Divide?
One of the biggest questions gardeners ask is whether to divide the clumps in the fall or wait until the spring. Both methods have benefits.
Dividing in the Fall
Many growers prefer to divide in the fall because the tubers are soft and easy to cut. It also takes up much less storage space to keep individual tubers rather than large clumps. The challenge is that the "eyes" can be very difficult to see in the fall. They are often just tiny, dormant bumps that are easy to miss.
Dividing in the Spring
Waiting until spring is often easier for beginners. After a few months of storage, the eyes will naturally begin to swell or even sprout, making it very obvious where to make your cuts. The downside is that the tubers become much tougher and more "woody" over the winter, requiring a very sharp knife and more physical effort to divide.
If you are new to the process, we suggest storing the clumps whole. This protects the fragile necks and gives you a better chance of seeing the eyes clearly when you are ready to plant in the spring.
Creating the Perfect Storage Environment
The goal of storage is to keep the tubers dormant, cool, and plump. If it is too warm, they will sprout early or rot. If it is too cold, they will freeze. If it is too dry, they will shrivel up like raisins.
Temperature and Humidity
The ideal storage temperature is between 40°F and 50°F. A cool basement, a root cellar, or a frost-free crawlspace are usually the best locations. Aim for high humidity but avoid direct wetness.
Storage Mediums
You shouldn't just throw the tubers into an empty box. They need a packing medium to help regulate moisture. Popular choices include:
- Peat moss: Excellent for holding just enough moisture.
- Vermiculite: A sterile mineral that provides great insulation.
- Wood shavings: Often sold as animal bedding, these are affordable and effective.
- Sand: Good for preventing shriveling but makes the boxes very heavy.
Place a layer of your chosen medium in a cardboard box or a plastic bin. Lay the tubers or clumps on top, ensuring they do not touch each other. If one tuber starts to rot, you don't want it to spread to the rest. Cover them with another layer of medium and repeat. If using plastic bins, leave the lid slightly ajar or drill small holes in the sides to allow for air exchange.
Key Takeaway: Check your tubers once a month during the winter. If they look shriveled, lightly mist the packing medium with water. If you see any soft or moldy spots, remove those tubers immediately to save the rest of the collection.
Troubleshooting Common Digging Challenges
Even with the best care, you might run into a few hurdles. Here is how to handle the most common situations.
Heavy Clay Soil
If your soil is like concrete, digging can be a workout. Do not try to pry the clump out all at once. Take smaller "bites" with your fork around the perimeter. If the soil is very dry, watering the area a day before you plan to dig can help soften the ground.
Broken Necks
If you accidentally snap a tuber neck, don't worry. It happens to everyone. If the clump is large, you likely have plenty of other healthy tubers attached. Simply trim off the broken piece and move on.
No Visible Eyes
If you can’t find the eyes, don’t panic. Some varieties are "blind" in the fall, meaning their eyes are very slow to develop. This is the perfect reason to store the clump whole. By spring, the eyes will almost certainly reveal themselves.
Pests in the Tubers
Occasionally, you might find holes in your tubers caused by insects. This is usually not a dealbreaker. As long as the tuber is firm and the crown is healthy, the plant will likely be fine. If a tuber is hollowed out or feels soft and mushy, it is best to discard it.
The Reward of the Harvest
While the process of digging may seem like a lot of work, it is a labor of love that pays off in spades. Saving your tubers allows you to grow larger, more impressive plants each year. As the clumps grow, you will eventually have enough tubers to share with friends, family, and neighbors.
Gardening is a cycle of growth and rest. Digging your dahlias is the final act of the season, a way to tuck your garden into bed for the winter. It provides a quiet moment of reflection on the beauty of the past summer and builds anticipation for the year to come.
Practical Scenarios for the Home Gardener
Understanding the theory is great, but real-world conditions often vary. Here are a few ways to adapt the digging process to your specific situation.
Scenario A: The Busy Gardener
If you have a busy schedule and can't wait a week after the frost, you can cut and dig on the same day. The tubers will still be healthy. Just be extra careful when lifting, as the skins will be thinner and more susceptible to bruising.
Scenario B: The Small Space Gardener
If you only grow a few dahlias in pots, the process is even simpler. Cut the stems back and move the entire pot into a cool, dry area like a garage. You can leave the tubers in the soil all winter. In the spring, simply dump the pot out, refresh the soil, and divide the tubers then.
Scenario C: The Wet Autumn
If your fall has been exceptionally rainy, your tubers may be very saturated. In this case, washing them with a hose might add too much moisture. Instead, let the clumps sit on a newspaper or a wire rack for a few extra days to ensure they are dry to the touch before putting them into storage bins.
Conclusion
Digging and storing dahlia tubers is one of the most satisfying "easy wins" in the garden. By following these simple steps, you can protect your favorite varieties from the winter chill and ensure a spectacular show of blooms next summer. Remember that gardening is a learning experience, and every season offers a chance to refine your technique.
- Wait for the first frost to signal dormancy.
- Lift carefully with a garden fork to protect the tuber necks.
- Label your varieties immediately to avoid confusion.
- Store in a cool, dark place with a moisture-regulating medium.
At Longfield Gardens, we believe that every gardener can find success with these beautiful flowers. By taking the time to care for your tubers now, you are setting the stage for a more beautiful and bountiful yard next year. If you want more ideas for next season, browse our Dahlia Collections.
The secret to dahlia success isn't just in the planting; it's in the careful preservation of the life that lives beneath the soil. For more information on caring for your summer favorites, explore our All About Dahlias guide.
FAQ
Can I dig up my dahlias before the first frost?
Yes, you can dig them up early if you need to. Ensure the plants have been in the ground for at least 120 days so the tubers are mature. Cutting the stems back a few days before you dig will help the plant begin its transition into dormancy even without a frost.
Do I have to wash the dirt off the tubers?
Washing is optional and depends on your soil. If you have sandy soil, a simple brush-off is enough. If you have heavy clay, washing helps you see the "eyes" and ensures you aren't storing pests or rot-inducing bacteria. Just make sure the tubers dry completely before they go into boxes.
What happens if I don't dig up my dahlias?
In zones 7 and colder, the tubers will likely freeze and rot over the winter. The high water content in the tubers causes them to expand and burst when the ground freezes solid. Digging them up is the only way to ensure they survive to bloom another year in cold climates. For a fuller overview, see our How to Overwinter Dahlias guide.
How do I know if a tuber is rotten?
A healthy tuber should feel firm, much like a fresh potato. If a tuber feels squishy, looks shriveled like a prune, or smells foul, it is likely rotting. You should cut away any soft or discolored parts until you reach clean, white flesh, or discard the tuber entirely to protect the rest of the clump.
