Table of Contents
- Introduction
- Why Storing Your Dahlia Tubers Is Worth the Effort
- When to Dig Your Dahlia Tubers
- Preparation: Steps to Take Before the First Frost
- How to Dig Dahlias Without Damaging the Tubers
- Cleaning and Curing Your Dahlia Tubers
- To Divide or Not to Divide: Fall vs. Spring
- Best Materials for Storing Dahlia Tubers
- Creating the Perfect Winter Storage Environment
- Monthly Maintenance: Checking on Your Tubers
- Preparing for Spring Growth
- Summary of the Storage Process
- FAQ
Introduction
There is nothing quite like the feeling of a garden filled with dahlias in late summer. These spectacular flowers offer a range of colors and shapes that few other plants can match. As the season winds down, you might feel a bit sad to see them go. However, one of the most rewarding parts of growing these flowers is knowing you can save them for next year. At Longfield Gardens, we want to help you preserve your favorite varieties so they can return to your garden even bigger and better.
Storing dahlia tubers is a simple skill that any gardener can master. Whether you are growing dinnerplate dahlias or dainty pompon varieties, the winter storage process is largely the same. We will guide you through the timing, digging, and packing methods that ensure your tubers stay healthy until spring. By following a few basic steps, you can turn a single season of beauty into a lifelong collection of blooms.
This guide covers everything you need to know about protecting your investment in dahlia tubers. We will walk you through the entire process from the first frost to the first signs of spring growth.
Why Storing Your Dahlia Tubers Is Worth the Effort
Dahlias are considered tender perennials in most parts of the United States. While they thrive in the heat of summer, they cannot survive freezing ground temperatures. If you live in a region where the ground freezes (typically USDA zones 7 and colder), your dahlias will not survive the winter if left outdoors.
Saving your tubers is a great way to save money on your garden budget. A single dahlia plant often produces multiple new tubers by the end of the season. This means that by storing them correctly, you are essentially getting new plants for free. Over time, you can grow a massive cutting garden from just a few initial tubers.
Beyond the cost savings, storing tubers allows you to keep dahlia varieties that you truly love. Some dahlia colors and forms are unique, and you might not always find the exact same ones for sale the following year. Keeping your own stock ensures your garden remains consistent with your personal style.
When to Dig Your Dahlia Tubers
Timing is the most important factor when it comes to a successful harvest. If you dig too early, the tubers may not be fully mature. If you wait too long, you risk the ground freezing, which can destroy the tubers instantly.
The Role of the First Frost
In most areas, the signal to start the process is the first "killing frost." This is the night when temperatures drop low enough to turn the dahlia foliage black or dark brown. This usually happens in late autumn. While it might look a bit sad to see your vibrant plants turn to mush, this is actually a helpful transition.
When the top of the plant dies back, the energy from the foliage moves down into the tubers. This helps them "cure" and prepares them for dormancy. Most experienced gardeners wait about 10 to 14 days after the first frost before they start digging. This waiting period allows the tubers to develop a thicker skin, which helps prevent them from drying out during winter storage.
Planning for Warm Climates
If you live in a very warm climate where frost rarely occurs, you still need to give your dahlias a rest. If your plants have been growing for at least 120 to 150 days, you can initiate dormancy yourself. Simply cut the plants back to the ground in late November or December. This allows the tubers to rest before the next growing season begins.
Key Takeaway: Wait for the first frost to blacken the foliage before you begin digging. This natural signal tells the plant to move its energy into the tubers for winter survival.
Preparation: Steps to Take Before the First Frost
Successful storage actually begins while the plants are still blooming. It is much easier to manage your collection if you are organized before the cold weather hits.
Labeling Your Plants
Once the frost hits and the plants turn black, it is almost impossible to tell one variety from another. To avoid a "mystery garden" next year, label your plants while they are still in bloom. Use waterproof tags or garden markers to identify the name or color of each plant. You can tie these tags directly to the base of the main stem near the soil line.
Sanitizing Your Tools
Disease prevention is a quiet winner in the garden. Before you start digging or cutting, clean your shovels, forks, and shears. A quick wipe with a solution of one part bleach to ten parts water will kill any lingering bacteria or viruses. This ensures you don't accidentally move a problem from one plant to another during the harvest.
Reducing Water and Fertilizer
Stop fertilizing your dahlias in late summer, usually by mid-August. This encourages the plant to stop producing new green growth and start focusing on tuber development. You should also reduce supplemental watering as the days get shorter and cooler. If the soil is too wet when you dig the tubers, they are more likely to rot in storage.
How to Dig Dahlias Without Damaging the Tubers
Dahlia tubers are surprisingly fragile. They consist of a "crown," a "neck," and the "body" of the tuber. The neck is the thin part that connects the tuber to the main stem. If this neck is broken or cracked, the tuber will likely not grow in the spring.
Step-by-Step Digging Process
- Cut the stems: Use a pair of sharp loppers to cut the main stem of the plant. Leave about 4 to 6 inches of stem protruding from the ground. This serves as a "handle" and makes the clump easier to find.
- Loosen the soil: Start digging about 12 inches away from the stem. Use a garden fork rather than a shovel if possible. A fork is less likely to slice through the tubers. Dig straight down on all four sides of the plant to loosen the earth.
- Lift carefully: Gently pry the entire clump of tubers upward from beneath. Do not pull on the stem handle to lift the plant. Pulling can snap the fragile necks of the tubers. Instead, lift from underneath with the fork while supporting the clump with your hand.
- Remove excess soil: Once the clump is out of the ground, gently shake it to remove large chunks of soil. You can use a small stick or your fingers to poke away the dirt between the tubers, but be careful not to nick the skin.
Cleaning and Curing Your Dahlia Tubers
Once the tubers are out of the ground, they need a little bit of cleaning and drying before they go into their winter home.
To Wash or Not to Wash?
Gardeners are divided on whether to wash tubers with a hose. If you have heavy clay soil, washing is often necessary to see the "eyes" and check for damage. If you have sandy or loose soil, you can usually just brush the dirt off once it dries. If you do choose to wash them, use a gentle stream of water. Avoid high-pressure nozzles that might tear the skin.
The Curing Process
Curing is simply letting the tubers dry out slightly so they don't rot. Place your cleaned tubers in a cool, dry area that is protected from direct sunlight and frost. A garage, shed, or covered porch works well.
Lay them out on a piece of cardboard or a mesh screen. Let them sit for 24 to 48 hours. This allows the outer skin to toughen up. Do not leave them out for too long, or they will begin to shrivel. The goal is to have tubers that are dry to the touch but still feel firm and plump like a potato.
What to do next:
- Check each tuber for soft spots or signs of rot.
- Trim away any "mother roots" (the original tuber you planted in spring).
- Remove long, thin feeder roots that look like hair.
- Ensure the variety label is still firmly attached to the clump.
To Divide or Not to Divide: Fall vs. Spring
One of the most common questions we hear is whether you should divide your dahlia clumps in the fall or wait until spring. Both methods have benefits, and the right choice depends on your schedule and storage space.
Storing Whole Clumps
Many gardeners prefer to store the entire clump just as it came out of the ground. This is the simplest method and takes the least amount of time in the fall, especially for pompon varieties. Whole clumps tend to dry out less quickly than individual tubers because they have more bulk. The downside is that they take up much more room in storage.
Dividing in the Fall
Dividing means cutting the clump into individual tubers. Each tuber must have a piece of the "crown" (the area where the tuber meets the stem) and at least one "eye." An eye is a small bump or bud where next year’s growth will come from.
The benefit of fall division is that the tubers are softer and easier to cut. It also saves a lot of storage space. However, eyes can be very difficult to see in the fall because they are dormant. If you cut a tuber and it doesn't have an eye, it will never grow.
Dividing in the Spring
Waiting until spring is often easier for beginners. As the weather warms up, the eyes on the tubers will begin to swell and turn slightly pink or green. This makes it very easy to see exactly where to cut. The downside is that the tubers become very hard over the winter, making them much tougher to slice through.
Best Materials for Storing Dahlia Tubers
To keep tubers healthy, you need to surround them with a medium that manages moisture. You want a material that prevents them from drying out completely but doesn't hold so much water that they rot.
Vermiculite
Vermiculite is a popular choice among many collectors. It is a natural mineral that is very good at regulating moisture. It holds a tiny bit of humidity near the tuber without making it wet. It is also very lightweight, which makes the storage bins easy to move.
Peat Moss
Peat moss is a classic storage medium. It is naturally slightly acidic, which can help discourage some types of rot. If you use peat moss, make sure it is just barely damp. If it is bone dry, it will actually suck the moisture out of your tubers.
Wood Shavings or Sawdust
Pine or cedar shavings (the kind sold for animal bedding) are inexpensive and effective. They provide good insulation and allow for a small amount of air circulation. Avoid using shavings from pressure-treated lumber, as the chemicals can harm the tubers.
Newspaper and Plastic Wrap
Some gardeners wrap individual tubers in several layers of newspaper. This is a great way to keep them separated so that if one rots, the problem doesn't spread to the others.
Another modern method is the "Saran Wrap" technique. After cleaning and curing, individual tubers are wrapped tightly in plastic kitchen wrap. This seals the moisture inside the tuber. While this method saves space, it requires the tubers to be perfectly cured. If there is any excess moisture trapped inside the plastic, the tuber will rot quickly.
Creating the Perfect Winter Storage Environment
The location where you store your tubers is just as important as how you pack them. You are looking for a "Goldilocks" environment: not too hot, not too cold, and just the right amount of humidity.
Temperature Requirements
The ideal temperature for dahlia storage is between 40°F and 50°F. If the temperature drops below 32°F, the water inside the tubers will freeze, causing them to turn to mush. If the temperature stays above 60°F for too long, the tubers may think it is spring and start to sprout prematurely, or they may simply shrivel up and die.
A cool basement, an insulated crawlspace, or a corner of a garage that stays above freezing are usually the best spots. Avoid areas near furnaces, water heaters, or south-facing windows.
Managing Humidity
Dahlias prefer a humidity level of about 80% to 90%. In most homes, winter air is very dry. This is why we use storage mediums like peat moss or vermiculite.
If you are using plastic storage bins, keep the lids slightly ajar or drill a few small holes in the sides. This allows for a tiny bit of air exchange. If you use cardboard boxes, be aware that the cardboard will absorb moisture from the air and the tubers, so you may need to check them more often.
Light Levels
Tubers should be stored in total darkness. Light can trigger the tubers to wake up from dormancy too early. If your storage bins are clear plastic, consider covering them with a dark blanket or storing them inside a dark closet.
Key Takeaway: The perfect storage spot is dark, stays between 40°F and 50°F, and has a storage medium that prevents the tubers from drying out.
Monthly Maintenance: Checking on Your Tubers
Storage is not a "set it and forget it" task. To ensure a high success rate, you should check on your tubers about once a month throughout the winter.
What to Look For
When you open your storage bins, look for two main things: rot and shriveling.
- Rot: If you see a tuber that looks fuzzy, black, or feels mushy, remove it immediately. Rot can spread quickly to healthy tubers nearby. If a whole clump is affected, you may be able to cut away the rotten part and save the rest, but usually, it is safer to discard the infected piece.
- Shriveling: If the tubers look like wrinkled raisins, they are losing too much moisture. They should feel firm like a fresh carrot. If they are shriveling, use a spray bottle to lightly mist the storage medium with water. You don't want to soak them; just a little bit of humidity will help them plump back up.
Adjusting Your Setup
If you consistently find rot, your storage area might be too damp or have too little airflow. Try opening the lids of your bins a bit more. If you consistently find shriveled tubers, your storage area is likely too dry or too warm. You might need to move the bins to a cooler spot or add more packing material.
Preparing for Spring Growth
As late winter approaches, you will start to see signs of life. In March or April, you can bring your tubers out of storage and prepare them for planting.
Waking Them Up
If you stored your tubers in whole clumps, this is the time to divide them. The eyes should be easy to see now. Cut the clumps so that each tuber has a piece of the crown and at least one visible eye.
Place the tubers in a warm, bright spot for a few days to signal that it is time to grow. Some gardeners like to "pre-start" their dahlias in pots indoors about 4 to 6 weeks before the last frost date. This gives the plants a head start and results in earlier blooms.
Hardening Off
If you started your dahlias in pots, remember that they have been in a protected environment. Before planting them in the garden, you must "harden them off." This means gradually introducing them to outdoor conditions over a week or two. Start with an hour of shade outside and slowly increase their time in the sun and wind.
Summary of the Storage Process
Storing dahlias is a cycle that follows the rhythm of the seasons. While it takes a little bit of effort, the reward is a garden that grows more beautiful every year. Our team at Longfield Gardens is always excited to hear about your success stories as your dahlia collections expand.
- Label early while flowers are still blooming.
- Wait for the frost to signal dormancy.
- Dig gently to protect the fragile necks of the tubers.
- Cure for 24–48 hours before packing.
- Store in a cool, dark place between 40°F and 50°F.
- Check monthly for rot or shriveling.
"Gardening is a practice of patience and observation. By taking the time to care for your dahlia tubers during the winter, you are participating in a tradition that ensures the beauty of the past blooms again in the future."
We hope this guide gives you the confidence to save your dahlias this year. With a few simple tools and a cool corner of your home, you can keep your favorite flowers coming back season after season.
FAQ
Can I leave my dahlias in the ground if I use a lot of mulch?
In USDA zones 8 and warmer, you can often leave dahlias in the ground with a thick layer of mulch to protect them from light frosts. However, in zones 7 and colder, the ground will freeze deep enough to kill the tubers regardless of how much mulch you use. Lifting and storing them is the only way to ensure they survive in colder climates.
What happens if I accidentally break a tuber off the clump?
If a tuber breaks off and it does not have a piece of the "crown" (the central stem area) attached, it will not grow. This is because the "eyes" or growth buds only form on the crown, not on the body of the tuber itself. You can discard any broken tubers that don't have a piece of the stem attached.
Is it okay to store my tubers in the refrigerator?
While a refrigerator is cool and dark, it is usually too cold and too dry for dahlia tubers. Most refrigerators are kept around 35°F to 38°F, which is very close to the freezing point. Additionally, the low humidity in a fridge will cause tubers to shrivel quickly. A cool basement or insulated garage is a much better choice.
Should I use a fungicide before storing my tubers?
Some gardeners like to dust their tubers with sulfur powder or a fungicide to prevent rot. While this can be helpful, it is usually not necessary if you cure your tubers properly and maintain the right temperature and humidity. Focus on removing any soil and ensuring the tubers are dry to the touch before packing them away.