Table of Contents
- Introduction
- The Case for Washing Dahlia Tubers
- The Case for Not Washing Dahlia Tubers
- How Your Soil Type Affects the Decision
- Timing Your Digging and Cleaning
- The Importance of Drying (The "Quiet Winner")
- Choosing the Right Storage Environment
- Dividing in Fall vs. Spring
- Mid-Winter Check-Ups
- Troubleshooting Common Storage Challenges
- Preparing for Spring Planting
- Conclusion
- FAQ
Introduction
As the late summer garden begins to fade into the golden hues of autumn, there is nothing quite as satisfying as looking back at a season full of dahlia blooms. Those dinner-plate-sized flowers and intricate pompons are the reward for a summer of careful tending. At Longfield Gardens, we believe that the end of the season is just the beginning of the next one. Taking the time to properly tuck your dahlia tubers away for the winter ensures that you can enjoy those same beautiful varieties year after year.
One of the most common questions we hear from gardeners as the first frost approaches is whether they should wash their dahlia tubers before putting them into storage. The answer isn't a simple yes or no, as both methods can lead to great results for dahlia tubers. Your decision will likely depend on your soil type, how much space you have, and whether you plan to divide your tubers in the fall or wait until the spring.
This guide will walk you through the pros and cons of washing versus brushing your tubers. We will also cover the essential steps for curing and packing your dahlias to keep them plump and healthy until spring. Whether you are a beginner or a seasoned grower, these simple steps will help you protect your investment and look forward to another vibrant growing season.
The Case for Washing Dahlia Tubers
Many gardeners prefer to give their dahlia tubers a thorough cleaning before they go into winter storage. This approach is often called the "clean storage" method. Washing involves using a gentle stream of water from a garden hose to remove all traces of soil from the dahlia clumps.
Seeing the "Eyes" More Clearly
The primary reason to wash your tubers is to make the "eyes" easier to spot. The eyes are small, dormant buds located on the neck of the tuber, right where it meets the main stem. These eyes are essential because a tuber without an eye will not produce a new plant in the spring. If you plan to divide your dahlia clumps in the fall to save space or share with friends, washing off the dirt is almost a necessity. It allows you to see exactly where to make your cuts without damaging the delicate necks of the tubers.
Removing Pests and Soil-Borne Disease
Soil can sometimes harbor pests like slugs, snails, or insects that might try to snack on your tubers during the winter. By washing the clumps, you remove these hitchhikers. Additionally, if your garden struggled with any fungal issues during the summer, washing helps ensure you aren't packing that contaminated soil right next to your healthy tubers. A clean tuber is easier to inspect for signs of rot or "gall," which is a bumpy, cauliflower-like growth that should be discarded immediately to keep the rest of your collection safe.
Managing Heavy Clay Soils
If you garden in an area with heavy clay soil, you know how tenaciously it sticks to everything. Clay holds moisture for a long time, and if it stays wet against the tuber during storage, it can encourage rot. Washing away heavy clay allows the tubers to breathe and dry out more evenly. It also makes for a much cleaner indoor storage area, as you won't have dried mud crumbling off your tubers every time you check on them.
Key Takeaway: Washing is the best choice if you have heavy soil, plan to divide your tubers immediately, or want to perform a detailed health inspection of your stock.
The Case for Not Washing Dahlia Tubers
On the other side of the garden fence, many successful growers prefer to leave the dirt right where it is. This "natural" approach treats dahlia tubers much like potatoes or other root vegetables.
A Natural Protective Barrier
Leaving a light layer of soil on the tubers can act as a protective skin. In some storage environments, this bit of earth helps regulate the moisture levels immediately surrounding the tuber. If your storage area is very dry, like a modern basement with a furnace, that extra bit of soil can help prevent the tubers from shriveling or dehydrating too quickly.
Saving Time and Reducing Moisture Risk
Washing tubers adds a significant amount of moisture to the equation. If you wash your tubers, you must be absolutely certain they are 100% dry before you pack them away. Any lingering water trapped in the hollow stems or between the tubers in a clump can lead to rot within weeks. By skipping the wash and simply brushing off the loose dirt, you eliminate this risk. It is also a much faster process, which is a major plus if you are digging up dozens of plants in the chilly autumn air.
Ideal for Sandy or Loamy Soils
If you are lucky enough to have loose, sandy soil, you may find that most of the dirt falls off the tubers naturally as you lift them from the ground. In these conditions, washing provides very little extra benefit. A quick shake and a gentle brush with a soft-bristle brush are usually all it takes to get them ready for their winter nap.
How Your Soil Type Affects the Decision
Before you reach for the hose, take a look at the soil in your garden. The "Right Plant, Right Place" rule also applies to "Right Method, Right Soil."
- Sandy Soil: If your soil is gritty and falls away easily, skip the wash. The tubers will stay cleaner naturally, and you won't have to worry about the extra drying time.
- Loamy Soil: This is the middle ground. You can likely go either way. If the soil is damp when you dig, let the clumps dry for a few hours, then see if the soil brushes off easily.
- Clay Soil: If the soil comes up in large, heavy clods that encase the tubers, washing is usually the better path. It is difficult to brush away wet clay without snapping the fragile necks of the dahlia tubers.
Timing Your Digging and Cleaning
The best time to start the digging process is after the first frost has blackened the foliage. This frost signals the plant to go dormant and send its final burst of energy down into the tubers. If you live in a climate where it doesn't freeze, you can simply wait until the plants begin to yellow and fade in late autumn.
Once the foliage is dead, cut the stems back to about four to six inches above the ground. Some gardeners like to leave the tubers in the ground for a week or so after cutting them back to help the "eyes" pop and the skins toughen up, but this is optional. When you are ready to dig, use a garden fork or a spade to gently loosen the soil in a wide circle around the plant—at least 12 inches away from the stem. Dahlias can grow quite wide, and you want to avoid accidentally slicing through a tuber.
Action Steps for Cleaning Your Tubers:
- Lift carefully: Gently pry the clump upward from several sides before lifting.
- Shake off loose dirt: Give the clump a gentle shake to remove the easiest soil.
- Choose your method: Decide to wash with a gentle spray or let the soil dry for brushing.
- Trim the "mother" tuber: If you see the original tuber you planted in the spring (it often looks darker and more wrinkled), you can trim it away, as it is prone to rotting in storage.
- Label immediately: Use a waterproof marker to write the variety name directly on the skin of the tuber or attach a sturdy tag.
The Importance of Drying (The "Quiet Winner")
Whether you wash your tubers or not, the drying phase—also known as curing—is the most important step in the entire process. Curing allows the skin of the tuber to thicken slightly and ensures that any cuts or "wounds" from digging have a chance to callouse over.
If you washed your tubers, they will need about 24 to 48 hours to dry completely. Place them in a cool, shaded area with good air circulation. A garage or a covered porch works well, provided the temperatures stay above freezing. Do not leave them in direct sunlight, as this can cause them to shrivel or even "cook" the delicate tissue.
If you chose not to wash them, they still benefit from a day of air-drying. This makes the remaining soil easier to brush off and ensures the stems aren't holding excess water. Turn the clumps upside down during this time so any moisture trapped inside the hollow stems can drain out.
Key Takeaway: Moisture is the enemy of stored dahlias. Ensuring the tubers and stems are dry to the touch before packing is the best way to prevent rot.
Choosing the Right Storage Environment
Once your tubers are clean (or brushed) and dry, they need a home for the winter. The goal is to keep them dormant, which means keeping them cool but never freezing.
Temperature and Humidity
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, turning them into mush when they thaw. If the temperature stays above 55°F, the tubers may think it is spring and start to sprout prematurely, or they may simply dry out and shrivel up.
Humidity is the other half of the puzzle. You want the air to be somewhat humid (around 80% to 90%) so the tubers stay plump, but you need enough air circulation to prevent mold from growing.
Packing Materials
At us, we have found that several different packing materials work well to maintain this balance. You can choose based on what you have on hand:
- Peat Moss: This is a classic choice. It is naturally slightly acidic, which can help inhibit fungal growth, and it holds a bit of moisture without being "wet."
- Vermiculite: This lightweight mineral is excellent for regulating moisture. It absorbs excess humidity but releases it back if the tubers start to get too dry.
- Wood Shavings: Pine shavings (like the kind used for pet bedding) are a popular and affordable option. Avoid cedar shavings, as the oils in cedar can sometimes be too harsh for the tubers.
- Newspaper: If you have only a few tubers, wrapping each one individually in several layers of newspaper can work well.
Selecting a Container
Cardboard boxes, plastic bins, or paper bags are all viable options. If you use plastic bins, do not snap the lid on tight. Leave it cracked open or drill a few holes in the sides to allow for air exchange. If you use paper bags or cardboard, keep an eye on them, as they can sometimes draw too much moisture out of the tubers in very dry environments.
Dividing in Fall vs. Spring
The question of whether to wash often ties into when you plan to divide. There is no "right" time, only the time that works best for your schedule.
Dividing in the Fall
If you wash your tubers and divide them in the fall, you save a significant amount of storage space. Instead of storing large, bulky clumps, you are only keeping individual tubers. This also gives you a chance to inspect every single tuber for health before it goes into the bin. However, eyes can be harder to see in the fall, so you must be very careful when making your cuts.
Dividing in the Spring
Many gardeners prefer to store the clumps whole. The clump structure naturally helps protect the tubers from drying out. In the spring, the eyes will be much more prominent—sometimes even starting to sprout—making it incredibly easy to see exactly where to divide. The downside is that the clumps are much larger and require more packing material and storage space.
Mid-Winter Check-Ups
Gardening is a rewarding activity that doesn't completely stop when the snow falls. About once a month, it is a good idea to peek into your storage bins. This quick check takes the guesswork out of the process and allows you to make small adjustments.
- If you see rot: If a tuber feels soft or smells bad, remove it immediately. One rotting tuber can quickly spread to the rest of the bin.
- If you see shriveling: If the tubers look wrinkled like a raisin, they are too dry. You can lightly mist the packing material with a spray bottle of water. Do not soak them; just a tiny bit of moisture is enough to raise the humidity.
- If you see mold: Surface mold usually means there is not enough air circulation. Brush the mold off and leave the container open for a day or two to let things dry out.
Troubleshooting Common Storage Challenges
If you have struggled with storing dahlias in the past, don't be discouraged. Every home has a unique microclimate, and it often takes one or two seasons to find the "sweet spot" in your basement or garage.
Why Do My Tubers Rot?
Rot is almost always caused by too much moisture or poor air circulation. This can happen if the tubers weren't dried long enough after washing or if the storage bin was sealed too tightly. If you find rot frequently, try using a more "breathable" packing material like wood shavings or paper bags next year.
Why Do My Tubers Shrivel?
Shriveling happens when the air is too dry. Modern homes with central heating often have very low humidity in the winter. If your tubers are shriveling, try moving them to a cooler spot or storing them in plastic bins with only a few small air holes.
What If I Don't Have a Basement?
If you don't have a basement or garage, look for the coolest spot in your home. This might be a closet on an exterior wall, a crawl space, or even an unheated spare room. As long as the area stays between 40°F and 50°F and doesn't freeze, your dahlias will likely be just fine.
Preparing for Spring Planting
When the ground begins to warm and the threat of frost has passed, it is time for the most exciting part: bringing your dahlias back into the light. At Longfield Gardens, we recommend waiting until the soil temperature reaches about 60°F before planting your tubers directly into the garden.
If you stored your dahlias in clumps, this is the time to divide them. You will see small green or pink "nubs" (the eyes) starting to grow. Use a sharp, clean knife to separate the tubers, ensuring each one has at least one healthy eye and a solid neck.
If you want an early start on the season, you can "start" your tubers indoors in pots about four to six weeks before the last frost. This gives them a head start and can lead to earlier blooms in the summer. Simply place the tuber in a pot of damp potting soil, keep it in a warm, bright spot, and watch the magic happen.
Conclusion
Whether you choose to wash your dahlia tubers or simply brush off the dirt, the goal remains the same: keeping these beautiful plants safe and healthy through their winter dormancy. Washing is a fantastic tool for gardeners who want to divide their plants early or those who deal with heavy, sticky soil. Meanwhile, leaving the dirt on can provide a simple, natural layer of protection for those in drier climates.
By following these practical steps, you can take the intimidation out of dahlia care and treat it as a rewarding end-of-season ritual. Remember that success often comes down to the basics: dig carefully, dry thoroughly, and store cool.
- Washing makes eyes easier to see and removes pests.
- Leaving soil on can help prevent dehydration in dry storage.
- The most important step is ensuring tubers are dry before packing.
- Check your stored tubers monthly to catch any issues early.
We are here to support you in every step of your gardening journey, from the first spring planting to the final fall harvest. For more tips on growing beautiful dahlias, you can visit our planning guides or reach out to our team at Longfield Gardens. Happy gardening, and may your next season be your most beautiful one yet!
Final Thought: Your dahlia tubers are a living investment. A small amount of care in the fall leads to a spectacular explosion of color in the summer.
FAQ
Is it necessary to wash dahlia tubers before storing them?
No, washing is not strictly necessary. Many gardeners have great success simply brushing off loose soil and storing the tubers "dirty." Washing is most helpful if you have heavy clay soil or if you want to divide your tubers in the fall and need to see the "eyes" clearly.
How long should I let dahlia tubers dry after washing?
If you wash your tubers, you should let them air-dry for 24 to 48 hours in a cool, shaded spot with good air circulation. It is vital that the skin is dry to the touch and that no water is trapped inside the hollow stems before you pack them into storage materials.
What happens if I don't dry the tubers enough?
If dahlia tubers are packed away while they are still wet, they are very likely to rot. Excess moisture in a confined space encourages fungal growth and decay, which can quickly destroy an entire clump of tubers. Always prioritize thorough drying to ensure a successful winter storage.
Can I use a garden hose to wash the tubers?
Yes, a garden hose with a gentle spray nozzle is an effective way to clean tubers. Avoid using high-pressure settings, as the "necks" of the dahlia tubers are quite fragile and can snap easily. A gentle rinse is all you need to remove the soil and reveal the structure of the clump.