Table of Contents
- Introduction
- Knowing When to Start Digging
- Preparing the Plants for Lifting
- The Right Tools for the Job
- How to Dig Up Dahlia Tubers Safely
- Cleaning and Inspecting the Tubers
- To Divide or Not to Divide?
- Curing: The Essential Drying Phase
- Monitoring Your Tubers Through Winter
- Safety and Practical Considerations
- Summary of the Digging and Storage Process
- FAQ
Introduction
Dahlias are the undisputed stars of the late summer garden, offering a spectacular finale of color just when other plants begin to fade. From the massive, pillowy blooms of dinnerplate dahlias to the intricate geometry of pompons, these plants provide months of joy and armloads of fresh-cut flowers. At Longfield Gardens, we believe the only thing better than a season of dahlias is knowing you can enjoy those same beautiful varieties again next year.
While these dahlias are tropical in origin and cannot survive freezing ground temperatures, saving them for the next season is a straightforward and rewarding process. Digging up the tubers allows you to protect your investment and even expand your garden as the clumps grow larger over time. This guide will walk you through the simple steps of lifting, cleaning, and preparing your dahlia tubers for their winter nap.
Whether you are a first-time dahlia grower or looking to refine your technique, we have designed these steps to be practical and easy to follow. By focusing on a few key basics—proper timing, careful handling, and correct storage conditions—you can ensure your dahlia tubers return even stronger next spring.
Knowing When to Start Digging
Timing is one of the most important factors when learning how to dig up dahlia tubers. In most parts of the United States, the signal to begin comes from the weather. Dahlias are very sensitive to cold, and the first "killing frost" of the autumn is the traditional indicator that it is time to move them indoors.
A killing frost is easy to identify. One morning, you will head out to the garden and see that the once-vibrant green foliage has turned black or dark brown and appears wilted. This may look disappointing, but it is actually a helpful part of the plant’s natural cycle. When the top growth dies back, the energy from the plant moves down into the tubers, helping them "cure" and prepare for dormancy.
If you live in a region where a hard frost does not arrive until very late in the year, you should still plan to dig up your tubers by mid-November. The goal is to get them out of the ground before the soil itself freezes solid. Waiting too long can lead to the tubers rotting in cold, soggy soil or being damaged by deep freezes.
Key Takeaway: The best time to dig up dahlia tubers is about one to two weeks after the first killing frost has turned the foliage black. This brief waiting period allows the tubers to toughen up for storage.
Preparing the Plants for Lifting
Before you reach for your shovel, there are a few preparatory steps that make the digging process much easier and more organized. Clearing away the spent foliage helps you see exactly where the tubers are located and prevents you from accidentally damaging the "necks" of the tubers during the lifting process.
Cutting Back the Foliage
Start by using a sharp pair of bypass pruners or loppers to cut the main stems. You should leave a "handle" of the stem about 4 to 6 inches long protruding from the ground. This handle serves two purposes: it marks the center of the clump so you know where to dig, and it gives you a sturdy point to hold (but not pull!) as you loosen the soil.
Dispose of the foliage in your compost pile or green waste bin, provided the plants were healthy throughout the season. If you noticed any signs of disease or heavy pest pressure, it is better to discard the foliage in the trash to keep your garden bed clean for next year.
Labeling Your Tubers
One of the most common mistakes gardeners make is assuming they will remember which variety is which once the flowers are gone. Once the tubers are out of the ground, they all look remarkably similar.
Before you dig, attach a waterproof tag to the stem handle or have a marking system ready. You can write the variety name directly on the tuber later with a garden marker, but a temporary tag at the digging stage is a lifesaver. We recommend including the color and height on the tag if you have lost the original variety name.
The Right Tools for the Job
Choosing the right tool can make the difference between a successful harvest and a pile of broken tubers. While a standard pointed shovel can work, it is not always the best choice because the solid blade can easily slice through the tubers hidden beneath the soil.
A sturdy garden fork (sometimes called a digging fork or pitchfork) is the preferred tool for most gardeners. The tines allow you to move through the soil and lift the clump without creating a suction effect or accidentally severing the roots. If you have very heavy clay soil, a spade may be necessary, but you will need to be extra cautious about where you place the blade.
Make sure your tools are clean before you begin. If you are digging up several different varieties, it is a good practice to wipe your tools down between plants. This simple step helps prevent the spread of soil-borne issues from one part of the garden to another.
How to Dig Up Dahlia Tubers Safely
The actual process of lifting and storing dahlia bulbs requires a gentle touch. Dahlia tubers are often described as looking like a bunch of carrots or sweet potatoes joined at a central point called the "crown." The connection between the tuber and the crown—the neck—is very fragile. If the neck snaps, the tuber will usually not grow next year.
Step-by-Step Digging Technique
- Identify the Perimeter: Start by placing your garden fork in the soil about 12 inches away from the main stem handle. Digging too close is the most common cause of sliced tubers.
- Loosen the Soil: Push the fork deep into the ground and gently rock it back and forth. Move around the plant in a circle, loosening the soil on all sides. You want to "bridge" the clump of tubers from underneath.
- Lift with Care: Once the soil is loose all the way around, slide the fork under the center of the clump. Use one hand to stabilize the stem handle and the other to pry the clump upward with the fork.
- Avoid Pulling: Never try to pull the dahlia clump out of the ground by the stem alone. The weight of the soil clinging to the tubers can easily snap the necks. Always lift from underneath with your tool.
What to do next:
- Lift the clump gently out of the hole.
- Shake off the largest chunks of loose soil.
- Place the clump on the grass or a tarp nearby.
- Immediately check that the label is still attached to the correct plant.
Cleaning and Inspecting the Tubers
Once the tubers are out of the ground, they need to be cleaned so you can inspect them for health and prepare them for their winter storage container. The method you choose for cleaning often depends on your soil type.
Washing vs. Brushing
If you have light, sandy soil, you may be able to simply brush away the excess dirt with your hands or a soft brush once the tubers have dried for an hour or two. However, if your soil is heavy clay, the dirt often sticks in the crevices between the tubers.
In most cases, using a garden hose with a gentle spray setting is the most effective way to clean them. Washing the tubers allows you to see the "eyes" (the small bumps where next year's growth will emerge) and identify any soft spots or signs of rot. After washing, turn the clumps upside down so any water trapped in the hollow stems can drain out.
Inspecting for Quality
Take a close look at each clump. You are looking for firm, plump tubers. If you see any tubers that are mushy, shriveled, or significantly damaged by insects, use a clean knife to remove them. It is better to store a smaller, healthy clump than a large one that might harbor rot.
You might also notice the "mother tuber"—this is the original tuber you planted in the spring. It often looks darker and more wrinkled than the new tubers that grew during the summer. Some gardeners prefer to remove the mother tuber as it is more prone to rotting during storage, but it is not strictly necessary if it appears firm.
To Divide or Not to Divide?
This is a common question for home gardeners. Dividing dahlia tubers means cutting the large clump into individual pieces, each of which can grow into a new plant next year.
Why Divide in the Fall?
Dividing in the autumn saves a significant amount of storage space. Instead of storing large, bulky clumps, you are only keeping the individual tubers that are viable. It also allows the cut ends to callus over before they go into long-term storage.
Why Wait Until Spring?
Many beginners find it easier to wait until spring to divide. By March or April, the "eyes" of the tubers begin to swell and become much easier to see. If you divide in the fall, you must be very careful to ensure each piece has a portion of the "crown" (the area where the tuber meets the stem), as this is where the eyes are located. A tuber without an eye will never sprout, no matter how healthy it looks.
If you choose to store your clumps whole, you can always divide them in the spring when the growth points are obvious. This is often the safest path for new gardeners.
Curing: The Essential Drying Phase
Before you pack your dahlias away in a box or bin, they must go through a short drying period called curing. If you put wet tubers into a sealed container, they will likely rot within weeks.
At Longfield Gardens, we have found that several different materials work well for packing tubers. You can use:
- Peat Moss: Excellent for holding just the right amount of moisture.
- Vermiculite: A sterile mineral that provides great insulation and moisture control.
- Wood Shavings: Often sold as pet bedding, these are inexpensive and provide good airflow.
- Newspaper: If you have a very humid basement, wrapping tubers in several layers of dry newspaper can be enough.
Place a layer of your chosen packing material in the bottom of a cardboard box or a plastic bin with holes drilled in the sides for ventilation. Lay the tubers or clumps in the box so they are not touching each other, then cover them with more material.
Key Takeaway: Storing tubers in a breathable container with a packing medium like peat moss helps maintain the perfect balance of moisture, preventing both rot and dehydration.
Monitoring Your Tubers Through Winter
The job isn't quite finished once the box is tucked away. It is a good practice to check on your tubers about once a month during the winter. This allows you to catch small issues before they become big problems.
Open the boxes and feel a few of the tubers. If they feel extremely firm and plump, they are doing great. If they feel a little soft or look shriveled, you can lightly mist the packing material with water to increase the humidity. Be careful not to over-saturate them; a very light misting is all that is needed.
If you find a tuber that has become mushy or shows signs of fuzzy mold, remove it immediately and discard it. This prevents the rot from spreading to the healthy tubers in the box. Most gardeners expect to lose a small percentage of tubers over the winter, so don't be discouraged if one or two don't make it.
Safety and Practical Considerations
As you handle your dahlias, keep a few safety and practical points in mind. While dahlias are a delight in the garden, the tubers can be mildly toxic to dogs and cats if ingested, often causing stomach upset or skin irritation. It is best to keep your digging and storage area off-limits to curious pets.
Also, remember that every garden is a bit different. Your local microclimate, soil type, and the specific storage conditions in your home will affect how your tubers perform. Some dahlia varieties are naturally "better keepers" than others. Over time, you will learn which of your favorite dahlias are the easiest to store and which might need a little extra attention during the winter months.
Summary of the Digging and Storage Process
Digging up dahlia tubers is a rewarding way to wrap up the gardening season. By taking the time to protect these plants, you are ensuring a head start on a beautiful garden for the following year.
- Wait for the frost: Let the foliage turn black before you start.
- Dig wide and deep: Use a garden fork to lift the clumps without snapping the necks.
- Clean and cure: Wash away the soil and let the tubers dry for a few days in a protected area.
- Pack loosely: Use peat moss or shavings in a breathable container.
- Store cool: Aim for 40-50°F in a dark spot like a basement or insulated garage.
"Gardening is a cycle of anticipation and reward. Digging your dahlias is the final act of one season and the very first step toward the beauty of the next."
We hope this guide makes the process of saving your dahlias feel accessible and fun. With your tubers safely tucked away for the winter, you can spend the cold months planning new color combinations and looking forward to the first sprouts of spring. At Longfield Gardens, we love helping gardeners grow their skills alongside their cut flowers.
FAQ
Can I leave my dahlia tubers in the ground all winter?
In USDA hardiness zones 8 and warmer, you can often leave dahlia tubers in the ground if the soil provides good drainage and you apply a thick layer of mulch. However, in zones 7 and colder, the ground will freeze deep enough to kill the tubers, making it necessary to dig them up and store them indoors.
What happens if I dig my dahlias before the first frost?
You can certainly dig them up earlier if you have a short growing season or expect a very early freeze. However, the tubers may be smaller and the "skin" may be thinner. If you must dig early, try to wait until at least late September or early October to give the tubers as much time as possible to mature.
Do I need to wash the dirt off the tubers before storing them?
While some gardeners prefer to leave a little soil on the tubers, washing them is generally recommended. Clean tubers are easier to inspect for rot, disease, and "eyes." It also makes the dividing process much cleaner and prevents you from bringing soil-borne pests or fungi into your indoor storage area.
How do I know if a dahlia tuber is dead in the spring?
When you pull your tubers out of storage in the spring, they should feel firm, like a fresh potato. If a tuber is completely hollow, shriveled to a crisp, or mushy and smelling of decay, it is no longer viable. If it is firm but has no visible "eyes" yet, give it a few weeks in a warm spot to see if it sprouts before discarding it.