Introduction
Dahlias are the undisputed stars of the late-summer garden. Their bold colors and intricate shapes bring a sense of joy and abundance that few other flowers can match. At Longfield Gardens, we believe that the only thing better than a dahlia in bloom is knowing you can enjoy those same flowers year after year. While these plants are tropical at heart, saving them for the next season is a straightforward and rewarding process.
Taking out your dahlia tubers is one of the most satisfying fall garden tasks. It marks the end of a successful growing season and sets the stage for an even more beautiful display next spring. This guide is for any gardener who wants to protect their investment and learn the simple steps for harvesting and preparing tubers for their winter rest.
We will cover the best time to dig, the tools you need, and how to handle the tubers so they stay healthy. You will also learn how to identify the "eyes" and prepare the clumps for storage. Digging dahlias is an easy win for any gardener looking to grow a spectacular garden.
Understanding the Right Time to Dig
Timing is everything when it comes to harvesting dahlias. Because dahlias are native to the warm climates of Mexico and Central America, they do not handle freezing temperatures well. However, they do need a little bit of cold weather to tell them that the growing season is over. This transition period is essential for the health of the tubers.
In most parts of the United States, the signal to dig comes from the first frost. A light frost will usually singe the leaves, turning them brown or black. A "killing frost" is more significant and will turn the entire plant into a dark, wilted mass. While this might look a bit sad, it is actually a good sign. It tells the plant to stop putting energy into flowers and start storing it in the tubers below ground.
If you live in a region that does not get frost by mid-November, you can still take your tubers out. We recommend waiting until the plants have had at least 120 to 135 days of growth. This ensures the tubers are large enough and have enough energy to survive the winter. For those in USDA zones 8 and warmer, dahlias can often stay in the ground, but most gardeners in cooler zones will need to dig them up.
Key Takeaway: Wait for the first frost to blacken the foliage before you start digging. This signals the plant to move its energy into the tubers for winter storage.
Preparing the Plants for Harvest
Once the frost has arrived, you do not need to rush into the garden the very next morning. It is often better to wait a few days. Many experienced gardeners wait about a week after the first frost before digging. This short waiting period allows the tubers to "cure" slightly while still in the soil. It helps the skin on the tubers toughen up, which makes them less likely to be damaged during the digging process.
The first physical step is cutting back the foliage. Use a pair of sharp loppers or a garden saw to cut the main stem. You want to leave a "handle" that is about 4 to 6 inches long. This handle is very useful for identifying where the plant is, but you should never use it to pull the plant out of the ground.
During this stage, it is also vital to keep your labels organized. As soon as you cut the plant back, the distinct flowers are gone. If you have several varieties, like the massive Cafe au Lait or the vibrant dinnerplate types, you will want to know which is which next year. Tie a tag directly to the stem handle or place a marker firmly in the ground next to the clump.
Quick Prep Steps
- Identify which plants are which before the frost hits.
- Wait 3 to 7 days after the first frost for the tubers to mature.
- Cut the stems down to 4 or 6 inches above the soil line.
- Secure your variety labels to the remaining stem.
Essential Tools for Digging
You do not need fancy equipment to take out your dahlia tubers. Most of the tools are likely already in your garden shed. The goal is to move the soil without slicing into the fragile tubers.
A sturdy garden pitchfork is the best tool for this job. The tines of a pitchfork can slide through the soil and under the tubers with less risk of cutting them than a flat shovel. If you only have a shovel, that is fine, but you will need to be extra cautious about where you place your blade.
You will also want a pair of clean, sharp pruners. These are for trimming away small root hairs or any damaged parts of the tuber clump. Keeping your tools clean is a simple way to prevent the spread of soil-borne issues. A quick wipe with a diluted bleach solution or rubbing alcohol between different plants is a great practice.
How to Dig Without Damaging Tubers
The most common mistake when taking out dahlia tubers is digging too close to the stem. Dahlia tubers grow outward from the center in a circular clump. To keep them safe, you need to give them plenty of space.
Start by placing your pitchfork or shovel about 12 inches away from the main stem. This may seem like a lot of space, but it ensures you won't accidentally spear a tuber. Push the tool deep into the ground. You want to get underneath the entire clump.
Gently pry upward to loosen the soil. Move around the plant in a circle, loosening the soil from all sides. Think of it as gently coaxing the plant out rather than forcing it. Once the soil is loose all the way around, you can place one hand on the stem handle to steady the plant while you lift the clump with your tool from underneath.
If the soil is heavy or wet, the clump might be quite heavy. Lift with your legs and be patient. Once the clump is out of the ground, resist the urge to bang it against a hard surface to remove the dirt. Instead, use your fingers or a small stick to gently poke away the largest chunks of soil.
Key Takeaway: Always dig at least 12 inches away from the stem to avoid slicing the tubers. Use a pitchfork to lift the clump gently from underneath.
Cleaning and Inspecting the Tubers
Once the tubers are out of the ground, they need a bit of a cleanup. There are two schools of thought on washing dahlias. Some gardeners prefer to shake off the loose dirt and leave the rest, while others like to wash them completely clean with a garden hose.
At Longfield Gardens, we find that a gentle rinse is often helpful. It allows you to see the eyes more clearly and makes it easier to spot any signs of rot or damage. Use a low-pressure spray from your hose to wash away the mud. Avoid using high pressure, as the skin on freshly dug tubers is very thin and can tear easily.
After washing, take a close look at the clump. You are looking for firm, plump tubers. If you see any that are mushy, smelly, or look like they are rotting, trim them away immediately. Rot can spread to healthy tubers during storage, so it is best to remove it now. You should also trim off any long, thin "tail" roots. These don't contain energy for the plant and can often lead to mold in storage.
What to Look For
- Firmness: Tubers should feel like a firm potato.
- Color: Healthy tubers are usually tan or light brown.
- The Neck: The thin part where the tuber connects to the stem is called the neck. It must remain intact for the tuber to grow.
- The Eye: Look for small bumps or sprouts near the base of the stem. This is where next year's growth begins.
The Importance of Curing
Curing is the process of letting the tubers dry out slightly before they go into long-term storage. This step is essential because excess moisture is the primary cause of rot. If you put wet tubers into a box or bag, they will likely mold within a few weeks.
Find a cool, dry place that is out of direct sunlight and safe from frost. A garage, a basement, or a covered porch works well. Spread the tubers out in a single layer. You can place them on top of old newspapers, cardboard, or a wire rack for better air circulation.
Do not place your tubers directly on a concrete floor. Concrete can pull too much moisture out of the tubers, causing them to shrivel up. Let the tubers dry for 2 to 3 days. The goal is for the outer skin to feel dry and the remaining soil to be easy to brush off. If the weather is very humid, it might take an extra day or two.
To Divide or Not to Divide
One of the big questions gardeners face is whether to divide the clumps in the fall or wait until the spring. Both methods have advantages, and there is no wrong answer. It mostly depends on your available space and your comfort level.
Dividing in the Fall
If you have a lot of dahlias and limited storage space, dividing in the fall is a great option. Individual tubers take up much less room than large clumps. Additionally, the stems are softer and easier to cut in the autumn. The challenge is that the "eyes" can be very hard to see. Since a tuber will only grow if it has an eye, you must be careful when cutting.
Waiting Until the Spring
Many home gardeners prefer to store the clumps whole. In our trial gardens at Longfield Gardens, we often find that whole clumps store a bit better because they are less prone to drying out. By spring, the eyes will begin to swell and may even turn pink or green. This makes it much easier for a beginner to see exactly where to make the cuts.
Regardless of when you divide, the rule is the same: every piece must have a bit of the "crown" (the area where the tuber meets the stem) and at least one eye. A tuber without an eye is just a root and will not produce a plant.
Understanding the Anatomy: Crown, Neck, and Eye
To be successful when taking out and storing dahlias, you need to know a few basic parts of the plant. Understanding these terms makes the process much simpler and ensures you don't throw away viable tubers.
The Crown is the base of the main stem. This is the most important part of the plant because all the "eyes" are located here. When you divide a clump, you must ensure that a small piece of this crown remains attached to each tuber.
The Neck is the narrow part that connects the fat tuber to the crown. It is very fragile. If the neck gets bent or snapped, the connection is broken. Even if the tuber looks healthy, it will not be able to send energy to the eye to grow a new plant. Handle the clumps by the fat part of the tuber or the main stem, never by the thin necks.
The Eye is a small growth point, similar to the eye on a potato. In the fall, they look like tiny, raised bumps. This is where the new sprout will emerge. If you aren't sure if you see an eye, don't worry. It will become much more obvious as the weather warms up in the spring.
Final Preparations for Winter Storage
After the tubers have cured and you have decided whether to divide them, they are ready for their winter nap. The goal for winter storage is to keep them cool, dark, and slightly moist—but not wet.
Most gardeners use breathable containers like cardboard boxes, paper bags, or plastic crates. To help regulate moisture, you can pack the tubers in a medium like peat moss, vermiculite, or sawdust. These materials act as insulation and prevent the tubers from shriveling.
The ideal storage temperature is between 40°F and 50°F. If the area is too cold, the tubers will freeze and turn to mush. If it is too warm, they might start growing too early or dry out completely. A cool corner of a basement or an insulated crawl space is usually perfect.
What to do next:
- Check your stored tubers once a month during the winter.
- If they look shriveled, lightly mist the packing material with water.
- If you see any soft spots or mold, remove the affected tuber immediately.
- Keep your labels with the tubers so you are ready for spring planting.
Realistic Expectations for Success
It is important to remember that gardening is a partnership with nature. Even with the best care, not every single tuber will make it through the winter. Some varieties are naturally "better keepers" than others. For example, smaller tubers sometimes dry out faster than larger ones.
Weather also plays a role. A very wet fall might make the tubers more prone to rot, while a very dry winter might cause more shriveling. If you lose a few tubers, do not be discouraged. It is part of the process. Most gardeners find that the majority of their tubers survive and often provide enough new divisions to share with friends and neighbors.
Success with dahlias is about getting the basics right: timing the dig, protecting the necks, and managing moisture during storage. By following these simple steps, you can enjoy your favorite dahlia varieties for many seasons to come.
Conclusion
Taking out dahlia tubers is a rewarding way to wrap up the gardening season. It preserves the beauty of your garden and gives you a head start on next year’s blooms. By waiting for the frost, digging carefully with a pitchfork, and allowing the tubers to cure, you ensure they have the best chance of surviving the winter.
- Harvest after the first killing frost has blackened the leaves.
- Dig a wide circle around the plant to protect the fragile tubers.
- Clean, inspect, and cure the tubers for a few days before storing.
- Store in a cool, dark, frost-free location in breathable materials.
We are here to help you every step of the way as you grow your most beautiful garden yet. If you have questions about your dahlias or need advice on new varieties to add to your collection, don't hesitate to reach out to us at Longfield Gardens.
"Digging dahlias is not just a chore; it is the act of tucking your garden into bed so it can wake up even stronger next spring."
FAQ
Can I dig up my dahlias before the first frost?
Yes, you can dig them up earlier if you live in an area with a very late frost or if you need to clear the garden bed. However, it is best to wait until the plants have been growing for at least four months. This ensures the tubers have developed enough size and energy reserves to survive through the winter months in storage.
What should I do if I accidentally slice a tuber while digging?
Do not worry if you accidentally nick or cut a tuber. If the damage is on the fat part of the tuber and the neck is still firmly attached to the crown, the tuber will likely be fine. Simply trim off any jagged edges with clean pruners and let the cut area dry and "callous over" during the curing process before you put it into storage.
Do I have to wash the dirt off the tubers?
Washing is not strictly necessary, but it is highly recommended. Removing the soil makes it much easier to see the eyes, which are essential for dividing. It also allows you to spot any signs of rot or insect damage. If you choose not to wash them, at least shake off the loose soil and ensure they are dry before storing.
How long should I let dahlia tubers dry before storing them?
In most cases, 2 to 3 days of drying (curing) is sufficient. You want the surface of the tuber to feel dry to the touch and any remaining soil to be crumbly. Avoid drying them for more than a few days, as they can begin to shrivel. If the tubers start to look wrinkled like a prune, they have dried for too long and should be packed into storage immediately.
