Introduction
The end of the gardening season brings a special kind of satisfaction. After a summer filled with the spectacular colors and intricate shapes of dinnerplate dahlias, it is time to tuck these beauties away for their winter nap. Digging up tubers is a rewarding ritual that marks the transition from the vibrant chaos of summer to the quiet rest of winter. It is an act of looking forward, as each tuber you save today represents a bigger, more beautiful display in your garden next year.
At Longfield Gardens, we want to help you feel confident as you transition your garden from fall to winter. Saving your dahlias is one of the best ways to expand your flower collection without starting from scratch each spring. This guide is for any home gardener who wants to learn the specific timing and techniques for harvesting these roots safely and effectively. We will walk you through the signs that your plants are ready to be lifted and the best way to handle them so they stay healthy until spring.
By understanding the simple biological cues your plants give you, the process becomes much more intuitive. You do not need professional equipment or advanced degrees in botany to succeed. With a little patience and a sturdy garden fork, you can master the art of the dahlia harvest. For more varieties, browse our dahlia collections.
Understanding the Dahlia Life Cycle
To know when to dig, it helps to understand what is happening beneath the soil. Our All About Dahlias guide covers the full life cycle. Throughout the summer, your dahlia plants are not just producing flowers; they are also busy building storage organs called tubers. These tubers act like batteries, storing energy in the form of carbohydrates to fuel next year's growth.
In the late summer and early fall, as the days get shorter and the nights get cooler, the plant begins to shift its energy away from flower production and toward these underground roots. This process is called maturation. If you dig too early in the summer, the tubers may be small, thin, and lacking the energy reserves needed to survive the winter. Waiting until the end of the season ensures the tubers are firm, plump, and "mature."
A mature tuber has a thicker skin that protects it from drying out or rotting. This transition is triggered by changes in light and temperature. When the plant senses that winter is coming, it naturally begins to shut down its top growth. This is your signal that the energy has successfully moved downstairs into the root system.
When to Dig Up Dahlia Tubers
Timing is the most important factor in a successful dahlia harvest. While it can be tempting to clean up the garden as soon as the first leaves turn yellow, your dahlias benefit from staying in the ground as long as possible. However, you must get them out before the ground itself freezes solid.
The First Killing Frost
For most gardeners in the United States, the traditional signal to dig is the "first killing frost." A light frost might nip the petals of your flowers, but a killing frost will turn the entire plant—leaves, stems, and all—into a dark, wilted mass. While this might look sad at first, it is actually a very helpful marker.
When the foliage turns black or dark brown after a freeze, the plant has officially entered dormancy. The "blackening" indicates that the cells in the leaves have ruptured from the cold, and the plant will no longer be sending energy upward. This is the ideal time to begin the harvest process.
Waiting for Maturity
Once the frost has killed the top of the plant, many experienced gardeners wait another 7 to 14 days before they start digging. This "curing" period in the soil allows the tubers to toughen up. During these two weeks, the "eyes" (the small bumps where next year’s sprouts will emerge) often become more prominent and easier to see.
If you live in a region that does not experience frost until very late in the year, you can still dig your tubers. We recommend waiting until at least mid-to-late November. By this time, the plants have usually had enough time to develop sturdy tubers regardless of whether a freeze has occurred. If you are not sure which zone you garden in, check the Hardiness Zone Map.
Weather and Soil Conditions
If the forecast calls for an extended period of heavy rain or a deep, ground-freezing "hard freeze," do not feel like you must wait for the perfect two-week window. It is always better to dig a few days early in dry weather than to struggle with heavy, waterlogged soil or frozen ground.
Key Takeaway: The best time to dig is about one to two weeks after the first killing frost has blackened the foliage. This allows the tubers to finish maturing and makes the eyes easier to identify.
Preparing the Plants for Harvest
Before you reach for your shovel, there are a few preparation steps that make the job much easier. Proper preparation protects the fragile tubers and keeps your garden organized.
Cutting Back the Stems
Once the foliage is dead, use a pair of sharp loppers or garden shears to cut the main stalks. You should leave a "handle" of about 4 to 6 inches of stem sticking up out of the ground. These handles serve two purposes: they make it easier to see exactly where the center of the root clump is, and they give you something to hold onto while you gently lift the plant.
Be careful when cutting. Dahlia stems are hollow, and water can sometimes collect inside them. Some gardeners choose to cover these cut stems with a small piece of aluminum foil if heavy rain is expected before digging, which helps prevent water from sitting in the crown and causing rot.
Labeling Your Varieties
This is arguably the most important step in the entire process. Once the flowers are gone and the stems are cut, it is almost impossible to tell one variety from another. If you have a favorite dinnerplate dahlia and a PomPon Dahlia variety, you will want to know which is which come springtime.
We suggest attaching a waterproof tag directly to the 6-inch stem handle. You can use plastic garden labels, masking tape, or even write directly on the tuber later with a garden marker. Ensure the name is clear and the tag is securely fastened so it does not fall off during the digging process.
Cleaning the Area
Clear away the dead foliage and any weeds around the base of the plant. This gives you a clear view of the soil surface. It also prevents old plant debris—which might harbor pests or fungi—from getting mixed into your storage containers later.
Tools You Will Need
You do not need many tools to dig dahlias, but using the right ones will prevent unnecessary damage to the tubers.
- Garden Fork (Pitchfork): This is the preferred tool for most gardeners. The tines can slide into the soil with less resistance than a solid shovel blade, reducing the chance that you will accidentally slice through a tuber.
- Spade or Shovel: If you have very sandy soil, a shovel works well. In heavy clay, a fork is almost always better.
- Pruning Shears or Loppers: For cutting back the heavy stalks.
- Soft Brush: An old paintbrush or a soft-bristled hand brush is useful for removing loose soil.
- Garden Hose: For washing the tubers if your soil is sticky or heavy.
How to Dig Up Dahlia Tubers: Step-by-Step
Digging up a dahlia clump requires a gentle touch. Dahlia tubers are attached to the central stem by a "neck." This neck is very fragile; if it breaks or cracks, the tuber will likely rot and will not be able to grow a new plant next year.
Step 1: The Twelve-Inch Rule
Start by identifying the main stem. Position your garden fork about 12 inches away from the stem. Dahlia tubers grow outward in a circular pattern, and digging too close is the most common way gardeners accidentally damage the roots.
Insert the fork straight down into the soil. Do not pry yet. You want to loosen the soil in a circle all the way around the plant first.
Step 2: Loosening the Soil
Go around the entire plant, pushing the fork deep into the earth at 12-inch intervals. Gently rock the fork back and forth to break the suction of the soil. This "encircling" method ensures that the long feeder roots are loosened before you attempt to lift the main weight of the clump.
Step 3: The Big Lift
Once you have loosened the soil in a full circle, slide the fork deep under the clump at an angle. Use one hand to hold the stem handle and the other to operate the fork. Apply gentle upward pressure with the fork while providing a little support with the handle.
The goal is to let the fork do the work. The clump should lift out of the ground with the soil still attached. If you feel significant resistance, stop and loosen the soil a bit further out. Never "yank" the plant up by the stem, as this is how necks are broken.
Step 4: Removing Excess Soil
Once the clump is out of the ground, set it gently on the surface. Use your hands or a small stick to poke away the large chunks of soil. If your soil is dry and sandy, much of it will fall away easily. If you have heavy clay soil, the dirt may cling tightly to the tubers.
If the soil is very stubborn, you can use a garden hose with a gentle spray setting to wash the tubers clean. Washing makes it much easier to see the condition of the roots and helps you spot any signs of damage or disease.
What to Do Next
- Lift the clump and shake off large clods of dirt.
- Check for "mother tubers" (the original wrinkled tuber you planted) and decide if they should be removed.
- Inspect for firm, healthy tubers and discard any that feel mushy or hollow.
- Keep the variety label with the clump at all times.
Post-Harvest Care and Inspection
Once the tubers are out of the ground and relatively clean, they need a little bit of attention before they go into long-term storage.
Curing the Tubers
Tubers should not go directly from the damp ground into a sealed box. They need to "cure" or dry out slightly. Place your cleaned clumps in a frost-free, shaded area like a garage or a covered porch. Turn them upside down so that any water trapped in the hollow stems can drain out.
Let them dry for 24 to 48 hours. You want the surface of the tuber to be dry to the touch, but you do not want them to sit out so long that they begin to shrivel. A light drying period toughens the skin and helps prevent mold during the winter.
Inspecting for Health
Take a close look at each clump. Healthy tubers should feel firm, like a fresh potato. If you see any tubers that are clearly rotten, mushy, or have large holes from insects, use a clean pair of snips to remove them. This prevents rot from spreading to the healthy parts of the clump.
You may also see the "mother tuber." This is the tuber you originally planted in the spring. It is often darker, more wrinkled, and larger than the new tubers. Some gardeners prefer to remove the mother tuber because it is more prone to rotting over the winter, though it is not strictly necessary if it still feels firm.
To Divide or Not to Divide?
A common question is whether you should divide the large clump into individual tubers in the fall or wait until spring.
Dividing in the fall is easier because the tubers are softer and easier to cut. However, the "eyes" can be harder to see. Dividing in the spring is more difficult because the tubers become woody and tough, but the eyes will be starting to swell, making it obvious where to cut.
If you are a beginner, we often suggest keeping the clumps whole for the winter. This protects the fragile necks and gives you a better chance of success. You can always divide them in the spring when the plant's growth points are clear.
Regional Differences in Timing
While the "first frost" rule is a great general guideline, your specific location in the United States will influence your strategy, and our Shipping Information page can help you plan by zone.
Northern Climates (Zones 3-6)
In these regions, the ground freezes deep and fast. You must dig your dahlias. Usually, this happens in October or early November. If you wait too long, the tubers will freeze in the ground and turn to mush.
Transitional Climates (Zone 7)
Gardeners in Zone 7 are in a "swing" area. In a mild winter, dahlias might survive in the ground if they are heavily mulched. However, a sudden cold snap can still destroy them. We recommend digging them up to be safe, or at the very least, providing a 6-inch layer of straw or wood chips over the site.
Southern and Coastal Climates (Zones 8-11)
In warm areas where the ground does not freeze, you can often leave dahlia tubers in the ground year-round. However, many gardeners still choose to dig them up every two or three years. This prevents the clumps from becoming too crowded, which can lead to smaller flowers and weaker stems.
Successful Storage Basics
While this guide focuses on digging, the way you dig directly affects how well the tubers store. For more details, see How to Keep Dahlia Bulbs Over the Winter. The goal of storage is to keep the tubers dormant, cool, and just moist enough that they do not shrivel.
- Temperature: Aim for 40°F to 50°F. A cool basement, crawl space, or insulated garage is usually perfect.
- Medium: Store tubers in a material that breathes but holds a tiny bit of moisture, such as peat moss, vermiculite, or pine wood shavings.
- Check-ups: Once a month during the winter, peek inside your storage containers. If a tuber looks shrivelled, give the storage medium a very light mist of water. If one looks rotten, remove it immediately.
Common Digging Mistakes to Avoid
Gardening is a learning process, and even experienced growers make mistakes. Here are the most common ones and the simple ways to get it right:
Mistake: Digging too close to the plant.
- The Result: Sliced tubers that are prone to rot.
- The Fix: Always start your fork at least 12 inches away from the main stem.
Mistake: Lifting by the stem only.
- The Result: Broken necks, which renders the tuber unable to sprout.
- The Fix: Use the garden fork to lift the weight from underneath while using the stem only for balance.
Mistake: Forgetting to label.
- The Result: A "mystery box" of tubers in the spring.
- The Fix: Tag the stem handle before the clump even leaves the ground.
Mistake: Storing tubers while they are soaking wet.
- The Result: Rapid mold and rot.
- The Fix: Allow tubers to air dry in a garage for a day or two before packing them away.
Why We Dig
It might seem like a lot of work to dig up your garden every autumn, but the rewards are well worth the effort. Dahlias are unique because they multiply. One tuber planted in May can produce a clump of five to ten tubers by October. By digging and storing them, you are essentially creating a "flower bank."
Over time, you will have enough tubers to fill your entire yard, share with neighbors, or trade for White & Cream Dahlias. This process also gives you a chance to inspect your soil and prepare your garden beds for the following year.
At Longfield Gardens, we believe that the more you understand your plants, the more you will enjoy the time you spend with them. Taking the time to harvest your dahlias correctly ensures that your favorite varieties will return to bring color and joy to your summer landscape for years to come.
Final Key Takeaway: Digging dahlias is a gentle process of loosening the soil 12 inches away from the stem and lifting the clump from below to protect the fragile necks.
Conclusion
Digging up dahlia tubers is a simple, satisfying task that ensures your garden remains vibrant year after year. By waiting for the first frost, cutting back the stems properly, and lifting the clumps with a wide, gentle circle, you protect the energy the plants worked so hard to store all summer. Remember to label your varieties immediately and give them a short drying period before they go into storage.
- Wait for a killing frost to signal dormancy.
- Cut stems to 4-6 inches and label each variety.
- Dig at least 12 inches away from the stem to avoid damage.
- Allow tubers to cure in a dry, frost-free area for 24-48 hours.
The effort you put in now will pay off in spectacular blooms next season. For the best results, always start with high-quality stock and keep an eye on your local weather patterns. If you ever have questions about your plants or need to add new varieties to your collection, we are here to help, and you can browse the Dahlia Decorative Golden Hour Collection. Happy harvesting!
FAQ
Can I dig up my dahlias before the first frost?
Yes, you can dig them up before a frost if you need to, especially if you live in a region with a very late winter or if you are expecting heavy, prolonged rain. However, waiting until the foliage begins to die back ensures the tubers are fully mature and have a better chance of surviving winter storage.
What happens if I accidentally slice a tuber with my shovel?
If you slice a tuber, do not panic. If the cut is clean and the neck is still attached to the crown, the tuber may still be viable. Simply set it aside to dry so the cut can "callous" over. If the tuber is badly mangled or the neck is severed, it is best to discard that specific root and focus on the healthy ones in the clump.
Do I have to wash the dirt off the tubers?
Washing is not strictly required, but it is highly recommended if you have heavy or clay-rich soil. Cleaning the tubers allows you to inspect them for rot, pests, and the "eyes" needed for future growth. If you have very sandy, loose soil, you can often just brush the dirt off with your hands or a soft brush.
How do I know if a dahlia tuber is "dead"?
A healthy tuber should feel firm and heavy, similar to a potato. If a tuber feels hollow, "squishy," or looks like a shrivelled raisin, it is likely dead or rotten. You can also nick the skin slightly with a fingernail; if you see white, creamy flesh inside, the tuber is alive. If it is brown or black all the way through, it should be discarded.
