Table of Contents
- Introduction
- To Wash or Not to Wash: The Big Debate
- Why You Might Choose to Wash Your Tubers
- Why You Might Skip the Wash
- The Role of Soil Type in Your Decision
- The Critical Step: Drying After Washing
- Understanding Tuber Anatomy Before You Wash
- Storage Success: Beyond Washing
- When to Divide Your Tubers
- Troubleshooting Common Storage Issues
- A Note on Safety: Kids and Pets
- Shipping and Arrival: What to Expect
- Choosing Varieties for Your Collection
- Summary Checklist for Washing Tubers
- Conclusion
- FAQ
Introduction
Growing dahlias is one of the most rewarding experiences a gardener can have. There is a special kind of magic in watching a small, potato-like tuber transform into a towering plant covered in dinnerplate-sized blooms. When the growing season winds down and the first frost arrives, it is time to lift those tubers and prepare them for their winter nap. At Longfield Gardens, we want to make sure your favorite varieties return year after year with vigor.
One of the most common questions we hear during the autumn digging season is whether you should wash your dahlia tubers before putting them into storage. The answer is not a simple yes or no, as both methods can lead to success depending on your specific situation. This guide will help you understand the benefits of each approach and how to choose the one that fits your garden best. Whether you are a first-time dahlia grower or a seasoned pro, the goal is to keep those tubers healthy, plump, and ready for spring. For more growing basics, see 8 Tips for Growing Better Dahlias.
The decision to wash dahlia tubers depends on your soil type, your storage environment, and whether you plan to divide your clumps now or in the spring.
To Wash or Not to Wash: The Big Debate
When you lift a dahlia clump from the earth, it often comes up with a significant amount of soil attached. Some gardeners prefer to spray every bit of dirt away until the tubers are "kitchen clean," while others believe leaving the soil on provides a protective layer. Neither group is wrong; they are simply using different strategies to achieve the same result: a viable tuber for next year.
The "washers" argue that clean tubers are easier to inspect for disease and pests. It is much easier to spot a soft spot of rot or the tiny "eyes" that will become next year's stems when the tuber is clean. Additionally, if you plan to store your dahlias in a finished basement or a spare closet, bringing in clean tubers prevents a muddy mess in your home.
The "non-washers" often point to the way potatoes are stored. Dahlias and potatoes are both starchy storage organs that naturally live in the soil. Leaving a bit of native earth on the tuber can help maintain a consistent moisture level and prevent the skin from drying out too quickly. This method is also a major time-saver if you have dozens of plants to process before the ground freezes.
Key Takeaway: Washing is a preference, not a requirement. Clean tubers are easier to inspect and divide, while unwashed tubers are faster to process and may stay hydrated longer in dry storage.
Why You Might Choose to Wash Your Tubers
Washing is the preferred method for many hobbyists and professional growers for several practical reasons. If you are leaning toward giving your dahlias a bath this fall, here are the primary benefits you will enjoy.
Easier Inspection for Rot and Pests
The health of your dahlia collection depends on storing only sound, firm tubers. When tubers are covered in mud, it is easy to miss a small patch of rot or damage from a garden fork. Washing allows you to see the entire surface of the tuber. You can quickly identify any "mushy" spots that need to be trimmed away before they spread to the rest of the clump. It also helps you spot any stowaways, like slugs or insects, that might try to hitch a ride into your storage area.
Better Visibility of the "Eyes"
If you plan to divide your dahlia clumps in the fall, washing is almost mandatory. To successfully divide a dahlia, each piece must include a portion of the "crown" with at least one viable eye. These eyes are small bumps where the new growth will emerge in the spring. They can be very difficult to see when they are caked in dirt. A clean tuber makes the anatomy of the plant much clearer, reducing the risk of making a wrong cut and losing a potential plant.
Cleaner Indoor Storage
Many gardeners store their tubers in plastic bins or crates inside their homes, such as in a basement or a cool utility room. Washing the tubers outdoors with a hose prevents you from bringing buckets of garden soil into your living space. Clean tubers can be packed neatly into fresh peat moss or vermiculite, keeping your storage area tidy and organized.
What to do next:
- Use a gentle stream of water to avoid bruising the tuber skins.
- Check the "neck" area where the tuber meets the stalk for any signs of breakage.
- Trim away any thin, spindly roots that do not have a tuber attached.
- Label each clump immediately after washing so you don't lose track of the variety.
Why You Might Skip the Wash
While washing has its perks, many successful gardeners find that leaving the soil on produces excellent results with much less effort. Here is why you might decide to skip the hose this year.
Natural Moisture Retention
Soil acts as a natural insulator. If your storage area has very low humidity, unwashed tubers often hold onto their internal moisture better than washed ones. The thin layer of dirt slows down the evaporation process, which can prevent the tubers from shriveling. This method is particularly helpful if you live in a dry climate or use a storage method that doesn't involve a packing medium like peat moss.
Time and Resource Efficiency
Digging dahlias can be a big job, especially if you have a large collection. Washing each clump, waiting for it to dry, and then packing it away adds several hours (or even days) to the process. If a hard freeze is coming or you have a busy schedule, skipping the wash allows you to get the tubers out of the danger zone and into a protected environment much faster.
Less Risk of Mechanical Damage
The skin of a dahlia tuber is relatively soft when it first comes out of the ground. High-pressure water or vigorous scrubbing can actually nick or tear the skin. These small wounds can become entry points for fungus or bacteria during the winter. By handling the clumps less and leaving the soil intact, you minimize the risk of physical damage to the tubers.
Key Takeaway: If you have sandy soil that falls away easily or if you plan to store your tubers in a root cellar, skipping the wash is a safe and efficient choice.
The Role of Soil Type in Your Decision
Your garden's soil composition plays a major role in how easy or difficult it is to process your tubers. Not all "dirt" behaves the same way when it is time to lift your plants.
Dealing with Heavy Clay
If your garden is rich in clay, you may find that it clings to the tubers in heavy, sticky chunks. This soil can become like concrete as it dries, making it very difficult to remove later without breaking the fragile necks of the tubers. In this case, a gentle wash is often the best path. It is much easier to rinse away wet clay than it is to chip away dry clay in the spring.
Managing Sandy Soil
Gardeners with sandy soil have it much easier. Usually, a few gentle shakes are enough to make the majority of the soil fall away from the clump. If your tubers come out of the ground looking relatively clean, there is very little reason to add the extra step of washing them. You can simply brush off the remaining loose grains and move straight to the curing phase.
The Critical Step: Drying After Washing
If you do decide to wash your dahlia tubers, the most important thing you can do is ensure they are properly dried before they go into storage. Storing wet tubers in a confined space is a recipe for mold and rot.
How to Dry Tubers Safely
After washing, place your tubers in a protected, well-ventilated area. A garage, a covered porch, or a cool basement works well. Do not leave them in direct, hot sunlight, as this can cook the tubers or cause them to shrivel too quickly.
Lay the clumps out on a tray, a piece of cardboard, or a mesh screen. Many gardeners find it helpful to turn the clumps upside down so that any water trapped in the hollow stalks can drain out. This prevents "stem rot," which can travel down into the crown and destroy the entire plant.
Finding the Sweet Spot
You want the surface of the tuber to be dry to the touch and the skin to feel slightly "cured" or toughened. This usually takes between 12 and 24 hours, depending on the humidity and airflow in your drying area. Do not let them sit out for days on end. If the tubers start to look wrinkled or feel soft and spongy, they have been out too long and are losing vital moisture.
What to do next:
- Place a fan in the room to increase airflow during the drying process.
- Check the tubers every 8 hours to monitor their progress.
- Ensure the hollow stems are completely dry before packing.
- Once the skin feels like a potato skin, they are ready for storage.
Understanding Tuber Anatomy Before You Wash
Before you start spraying, it is helpful to know what you are looking at. For a closer look, see Dahlia Tubers: What You Need to Know. A dahlia clump consists of several parts: the old mother tuber, the new tubers, the crown, and the stalk.
The mother tuber is the one you planted in the spring. By fall, it often looks a bit shriveled or dark. It has done its job and can often be removed, as it is more prone to rot in storage. The new tubers are the plump, firm ones that grew during the summer.
The "neck" is the narrow part that connects the tuber to the crown. This is the most fragile part of the plant. If the neck is broken or "strangled" by heavy, wet soil, the tuber will not grow next year, even if it looks healthy. When washing, be extremely careful around these necks. Support the weight of the clump from underneath so the tubers don't snap off under the pressure of the water.
Storage Success: Beyond Washing
Whether you wash or not, the environment where you keep your tubers will determine if they survive until spring. Dahlias are tropical plants and cannot survive a freeze, but they also don't like to be too warm. For climate context, check our Hardiness Zone Map.
The Ideal Temperature
The "Goldilocks" temperature for dahlia storage is between 40°F and 50°F. If the temperature stays in this range, the tubers will remain dormant. If it gets much warmer, they may try to sprout prematurely, which uses up their stored energy. If it drops below freezing, the water inside the tubers will expand, turning them into a mushy, black mess that cannot be saved.
Humidity and Airflow
High humidity (around 75% to 85%) is ideal to keep the tubers plump, but you also need enough airflow to prevent stagnant air from causing mold. This is why we often recommend storage mediums that "breathe."
Common Storage Mediums
- Peat Moss: This is a classic choice because it holds some moisture but doesn't stay soggy. It is also naturally acidic, which can help inhibit some types of fungal growth.
- Vermiculite: This mineral is excellent for maintaining a steady environment. It is lightweight and easy to use.
- Wood Shavings: Many people use pine shavings (like those used for pet bedding). These are very breathable but can sometimes dry the tubers out too much, so keep a close eye on them.
- Plastic Wrap: Some gardeners wrap individual, clean tubers tightly in plastic wrap. This seals the moisture inside. This method requires the tubers to be perfectly clean and dry on the surface before wrapping.
Key Takeaway: Successful storage is about balance. You want enough moisture to prevent shriveling but enough dryness and airflow to prevent rot.
When to Divide Your Tubers
The question of washing often goes hand-in-hand with the question of when to divide. Dividing is the process of cutting the large clump into individual tubers to increase your stock of plants.
Fall Division
If you have a lot of energy in the autumn and want to get the work out of the way, fall division is a great option. You must wash the tubers to see what you are doing. The benefit is that the tubers take up much less space in storage once they are divided. The downside is that the "eyes" can be very small and hard to find in the fall.
Spring Division
Many gardeners prefer to store the clumps whole and divide them in the spring. By March or April, the eyes will begin to swell and may even turn slightly pink or green. This makes it incredibly easy to see exactly where to cut. If you choose spring division, you don't necessarily need to wash the tubers in the fall; you can simply brush off the dirt and store them in their natural state.
Troubleshooting Common Storage Issues
Even with the best intentions, things can sometimes go sideways. If you check your tubers during the winter (which we recommend doing once a month!), here is how to handle common issues.
Signs of Rot
If you see a tuber that has turned black, feels slimy, or smells bad, remove it immediately. Rot can spread from one tuber to the next. If only a portion of a tuber is affected, you can sometimes cut the bad part off with a clean knife. At Longfield Gardens, we suggest keeping a close eye on your storage bins so you can catch these issues early.
Dealing with Mold
A little bit of white, fuzzy mold on the surface is usually not a death sentence. It often means the humidity is a bit too high or there isn't enough airflow. You can gently wipe the mold off with a soft cloth or a toothbrush. Try opening the lid of your storage container for a few days to let things dry out, or move the tubers to a slightly drier spot.
Rescuing Shriveled Tubers
If your tubers look like raisins, they are dehydrated. This is common if they were stored in wood shavings or left in a very dry room. You can often save them by lightly misting the packing medium with water. Don't soak them—just a little misting is usually enough to stop the shriveling.
A Note on Safety: Kids and Pets
While dahlias are beautiful in the garden, it is important to remember that they can be toxic if ingested. Dahlia tubers and foliage contain compounds that can cause skin irritation or digestive upset in humans and pets.
When you are digging, washing, and storing your tubers, keep them out of reach of curious dogs, cats, and small children. If you are washing them on a patio, make sure you rinse away any muddy runoff so pets don't accidentally lick it up. Always wash your hands after handling the tubers to avoid skin irritation.
Shipping and Arrival: What to Expect
If you are expanding your collection with new varieties, it is helpful to know how we handle things. See our Shipping Information. We ship our dahlia tubers to the 48 contiguous United States. We do not ship to Hawaii, Alaska, or international locations.
Our shipping schedule is based on your USDA hardiness zone. We time our deliveries so that your tubers arrive about two weeks before the ideal planting time in your area. This ensures they arrive in prime condition, ready to go into the ground or be started in pots. We typically use carriers like UPS and FedEx, so a street address is preferred. If you use a PO Box, please allow for a bit of extra transit time.
Once your order is picked up and scanned by the carrier, you will receive a tracking number so you can follow its journey to your doorstep. We stand behind the quality of our plants with a 100% Quality Guarantee. If your tubers arrive damaged or if there is a labeling issue, please contact us promptly after delivery so we can make it right.
Choosing Varieties for Your Collection
Whether you prefer washing or not, some dahlias are simply known for being "easy keepers." If you are new to storing tubers, you might want to start with varieties that are known for producing robust, firm tubers.
- Dinnerplate Dahlias: Varieties like ‘Café au Lait’ are famous for their beauty and generally produce good-sized tubers that store well.
- Dinnerplate Dahlias: ‘Thomas Edison’ is another classic choice with rich color and sturdy clumps.
- Ball Dahlias: Types like Jowey Winnie often create very dense, round tubers that are resistant to shriveling.
- Dinnerplate Dahlias: These giants, such as ‘Otto's Thrill’, produce large clumps that are easy to handle and divide.
- Dinnerplate Dahlias: ‘Kelvin Floodlight’ is another giant that is easy to handle and divide.
By selecting a mix of shapes and colors, you can ensure your garden is a showstopper from mid-summer through the first frost.
Summary Checklist for Washing Tubers
If you have decided that washing is the right path for your garden this year, follow this simple workflow to ensure success:
- Dig: Lift the clump gently with a digging fork, staying 12 inches away from the stem.
- Rinse: Use a garden hose with a gentle spray setting to remove soil.
- Inspect: Look for rot, pests, or broken necks.
- Trim: Remove the old mother tuber and any "stringy" roots.
- Label: Tie a waterproof tag or use a garden marker to identify the variety.
- Dry: Let the clumps air dry for 12–24 hours in a cool, shaded spot.
- Pack: Place in a breathable medium like peat moss or vermiculite.
- Store: Move to a dark spot that stays between 40°F and 50°F.
Conclusion
Deciding whether you should wash dahlia tubers ultimately comes down to your personal gardening style and the conditions of your storage space. Washing provides a clean slate, making it easy to spot problems and divide your plants with precision. On the other hand, leaving the soil on is a time-tested method that can protect tubers from drying out in less-than-ideal environments. Neither way is superior; they are simply tools in your gardening kit.
The most important factors for success are keeping the tubers frost-free, maintaining a balance of moisture, and checking on them occasionally throughout the winter. Gardening is a journey of discovery, and your dahlias are remarkably resilient plants that want to grow. For more ideas on long stems and bouquet-making, see How to Grow Dahlias for Cut Flowers.
Key Takeaway: Whether you prefer a sparkling clean tuber or one with a bit of garden "insulation," the goal is a healthy plant next spring. Pick the method that feels most achievable for you!
For a broader overview of growing and caring for these plants, see All About Dahlias.
We invite you to explore our selection of premium dahlia tubers at Longfield Gardens and start planning for your most beautiful summer yet. With a little bit of care this fall, your garden will be ready to burst into bloom once again when the warm weather returns.
FAQ
Should I use soap or bleach when washing my dahlia tubers?
No, you should only use plain water. Harsh chemicals or soaps can damage the sensitive skin of the tuber and may interfere with its ability to grow in the spring. If you are concerned about fungus, some gardeners use a very diluted fungicidal dip, but for most home gardens, clean water and proper drying are all you need.
Can I wash my tubers inside in a sink or bathtub?
It is best to wash tubers outside if possible. The soil that clings to dahlias can be very heavy and may contain small rocks or debris that can easily clog indoor plumbing. If you must wash them inside, use a large plastic tub to catch the water and soil, and then dispose of the muddy water in your garden rather than pouring it down the drain.
How do I know if my tubers are dry enough to store?
The surface of the tuber should feel dry and slightly "leathery," similar to the skin of a potato from the grocery store. There should be no visible moisture in the crevices where the tubers meet the crown. If the tubers feel slimy or wet, they need more time to dry. If they start to look significantly wrinkled, they are becoming too dry and should be packed away immediately.
What happens if I forget to wash them and the soil dries hard?
Don't worry! If the soil has dried into hard clumps, you can still store them that way. In the spring, you can soak the entire clump in a bucket of room-temperature water for about 20–30 minutes. This will soften the soil so it can be gently brushed away, allowing you to see the eyes and divide the tubers before planting.