Introduction
As the golden light of autumn settles over the garden, dahlias often take center stage. These late-season stars provide some of the most vibrant colors and impressive shapes of the entire growing year. Watching a dinnerplate dahlia reach full bloom in September is a high point for any gardener.
While dahlias are native to the warm climates of Mexico and Central America, they can easily become a permanent part of your garden in cooler regions. If you want to plan a similar display for next season, browse Dahlia Dinnerplate Cafe Au Lait.
The process of lifting, cleaning, and storing the tubers over the winter is a rewarding way to protect your investment. It also allows you to grow your collection, as one healthy plant can produce a surprising number of new tubers by the end of the season.
This guide will walk you through the simple steps of harvesting and preserving your dahlias. We will cover the best timing for digging, how to clean them without causing damage, and the ideal conditions for winter storage. With just a little bit of care, you can ensure your favorite varieties return even stronger next spring.
Timing the Harvest
One of the most important aspects of dahlia care is knowing when to start the harvest. While it can be tempting to dig them up as soon as the weather turns chilly, waiting for the right signals from nature ensures the tubers are mature and ready for dormancy. If you want to match your climate to your planting plan, check the Hardiness Zone Map.
The First Frost Signal
For most gardeners in the United States, the first light frost is the traditional signal to begin the process. You will notice the foliage start to darken or turn black after a cold night. This change tells the plant that the growing season is over.
When the top growth dies back, the plant shifts its energy downward. This "curing" phase in the soil helps the tubers toughen their skins and develop the "eyes" needed for next year’s growth. If you can, wait about a week or two after the first frost before you start digging. This brief waiting period makes the tubers more resilient during winter storage.
Harvesting Without Frost
If you live in a region where a killing frost comes very late, you don't have to wait forever. Most dahlias need about 120 to 150 days of growth to produce mature tubers. If it is late October or early November and frost hasn't arrived, you can proceed with the harvest anyway.
The goal is to get the tubers out of the ground before the soil itself freezes solid. Frozen soil can damage the tubers and lead to rot. If the weather forecast predicts a deep, sustained freeze, it is best to get outside and start your harvest a few days early.
Cutting Back the Stems
Before you reach for your shovel, you need to clear the way. Use sharp bypass pruners or loppers to cut the main stalks down. We recommend leaving a "handle" of about 4 to 6 inches of stem sticking out of the ground.
This handle serves two purposes. First, it makes it much easier to locate the center of the clump so you don't accidentally stab the tubers while digging. Second, it gives you something to hold onto as you gently lift the plant. Avoid cutting the stems all the way to the ground, as this can make it difficult to find the tubers and increases the risk of water entering the hollow stems and causing crown rot.
Key Takeaway: Wait for the first light frost to blacken the foliage, then cut the stems back to 6 inches. This timing ensures the tubers are mature and have started the curing process.
Digging the Tubers Carefully
Dahlia tubers grow in a clump, radiating outward from the central stem like a cluster of sweet potatoes. They are surprisingly fragile, especially at the "neck"—the narrow part where the tuber attaches to the main crown. A broken neck usually means the tuber will not sprout, so a gentle touch is essential. For a bold, time-tested favorite, look at Dahlia Dinnerplate Thomas Edison.
Choosing the Right Tools
A sturdy garden fork (sometimes called a digging fork) is the best tool for this job. Unlike a flat shovel, the tines of a fork can slide through the soil with less resistance. This reduces the chance of accidentally slicing through a hidden tuber. If you only have a shovel, make sure to give the plant an extra-wide berth.
The Lifting Technique
To lift the clump safely, follow these steps:
- Start about 12 inches away from the main stem on all sides.
- Push the fork deep into the soil and gently pry upward.
- Work your way around the entire plant in a circle, loosening the soil as you go.
- Once the soil is loose, place the fork underneath the clump and lift it gently from below.
Avoid the temptation to grab the stem handle and yank the plant out of the ground. Instead, use one hand to steady the handle while the fork does the heavy lifting. This prevents the weight of the soil from snapping the delicate necks of the tubers.
How to Clean Dahlia Tubers
Once the tubers are out of the ground, they will likely be covered in clumps of soil. Cleaning them is a vital step because soil can harbor fungi, bacteria, and pests that might cause problems during the long winter months.
Removing Bulk Soil
Start by gently shaking the clump to remove large pieces of loose dirt. You can also use your fingers or a soft brush to poke away soil from the center of the cluster. Be careful not to scrape the skin of the tubers, as any wounds can become entry points for rot.
Using Water for a Deep Clean
A garden hose is the most effective way to get your tubers truly clean. Set your hose nozzle to a gentle "jet" or "shower" setting. Wash the clump thoroughly, focusing on the area where the tubers meet the stem. This is the crown, and it is where the "eyes" will eventually appear.
Cleaning the crown allows you to inspect the health of the plant. If you see any soft, mushy, or foul-smelling areas, these are signs of rot and should be addressed immediately. We find that a clean tuber is much easier to store and monitor than one hidden under a layer of mud.
Sterilizing Your Workspace
If you are cleaning many different varieties, it is a good idea to keep your workspace tidy. For a striking mix of colors next year, consider the Dahlia Assorted Sunlit Jewel Collection. If you use tools to trim away small feeder roots or damaged pieces, dip them in a solution of one part bleach to ten parts water between plants. This simple step prevents the spread of soil-borne diseases from one variety to another.
What to do next:
- Rinse away all visible soil using a garden hose.
- Inspect the crown for any signs of soft spots or decay.
- Label each clump immediately with a waterproof marker or tag.
- Move the cleaned tubers to a shaded, frost-free area to begin drying.
Drying and Curing
You cannot put wet tubers directly into storage. Excess moisture is the primary cause of rot over the winter. The goal of the drying phase is to remove surface moisture and allow the outer skin of the tuber to toughen up slightly.
Finding the Right Spot
Place your cleaned tubers in a cool, dry area with good air circulation. A garage, a covered porch, or a basement works well. Avoid placing them in direct sunlight, as this can cause the tubers to shrivel or "cook."
It is also important to keep them off the bare ground or concrete. Concrete can pull moisture out of the tubers too quickly. Instead, lay them on a piece of cardboard, a wooden pallet, or a plastic crate. Some gardeners like to turn the clumps upside down so that any water trapped in the hollow stems can drain out.
How Long to Dry
In most cases, 24 to 48 hours is enough time for the surface of the tubers to dry to the touch. You want them to look dry but not shriveled. If the weather is very humid, it might take an extra day. Once the skin feels firm and the surface is no longer damp, they are ready for the next step.
Identifying and Dividing Tubers
One of the most common questions we receive is whether to divide the tubers in the fall or wait until the spring. Both methods work, and the choice often depends on how much storage space you have.
Dividing in the Fall
Many gardeners prefer to divide their dahlias in the autumn because the tubers are softer and easier to cut. Additionally, it takes up much less storage space to keep individual tubers than it does to store large clumps.
To be successful, a divided tuber must have three things:
- The Body: The fat part of the tuber that holds the energy.
- The Neck: The narrow part connecting the body to the crown.
- An Eye: A small bump or "bud" located on the crown (the piece of the old stem).
Without an eye, a tuber will grow roots but will never produce a sprout. In the fall, eyes can be very small and difficult to see. If you are a beginner, you might find it easier to leave the clumps whole or simply cut them into halves or quarters.
Storing Whole Clumps
If you have plenty of space, storing the entire clump is the simplest method. Whole clumps tend to resist shriveling better than individual tubers because they have more mass. You can always divide them in the spring when the eyes begin to swell and become much easier to identify.
Regardless of which method you choose, take a moment to trim away the thin, hair-like feeder roots and any tubers that are small, broken, or feel "squishy." Removing these unnecessary pieces helps prevent rot from starting and spreading to the healthy parts of the clump.
Packing Your Tubers for Storage
Proper packing is what keeps dahlia tubers in a state of "suspended animation." You want to prevent them from drying out completely (shriveling) while also ensuring they don't stay too damp (rotting).
Selecting a Storage Medium
You will need a material that can regulate moisture. Some of the most popular choices include:
- Peat Moss: Excellent at holding a tiny amount of moisture while staying fluffy.
- Vermiculite: A mineral that provides great insulation and moisture control.
- Pine Wood Shavings: Often sold as pet bedding, these provide good airflow.
- Coarse Sand: A traditional method that works well but can be very heavy.
The Packing Process
Use a breathable container such as a cardboard box, a plastic bin with holes drilled in the sides, or a heavy paper bag. For a mixed-color option next season, explore the Dahlia Dinnerplate Summer Lovin Collection.
- Place a 2-inch layer of your chosen medium at the bottom of the container.
- Lay the tubers or clumps on top so they are not touching each other.
- Cover them with another layer of medium.
- Continue layering until the box is full.
By ensuring the tubers do not touch, you create a "firewall." If one tuber happens to rot, the dry medium around it will help prevent the decay from spreading to its neighbors.
Key Takeaway: Pack tubers in a moisture-regulating medium like peat moss or vermiculite. Ensure they do not touch each other to prevent the spread of rot.
The Ideal Storage Environment
Location is everything when it comes to overwintering dahlias. The tubers are living things that are simply "sleeping," and they need specific conditions to stay healthy until spring.
Temperature is Key
The ideal temperature for storing dahlia tubers is between 40°F and 50°F.
- If it's too cold: If the temperature drops below freezing, the water inside the tubers will freeze and turn them into mush.
- If it's too warm: Temperatures above 50°F may signal to the plant that it’s time to wake up, causing them to sprout prematurely or dry out.
Unheated basements, crawl spaces, or insulated garages are usually the best spots. Check the temperature of your chosen spot with a simple thermometer to make sure it stays within the safe range.
Humidity and Airflow
Dahlias prefer a relatively high humidity (around 80%), but they also need a little bit of air circulation. This is why we recommend breathable containers. If your storage area is very dry, you may need to lightly mist the packing medium with water once or twice during the winter. If it is very damp, you might need to use more wood shavings or paper bags to absorb excess moisture.
Winter Checkups
Gardening doesn't entirely stop in the winter; it just moves indoors. We recommend checking on your stored tubers once a month. This small effort can save your entire collection.
What to Look For
When you open your storage boxes, look for two things:
- Signs of Rot: If you find a tuber that is soft, mushy, or has mold growing on it, remove it immediately and throw it away. Check the surrounding tubers to make sure they are still firm and dry.
- Signs of Shriveling: If the tubers look wrinkled like a raisin, they are losing too much moisture. Give the packing medium a very light misting of water. Do not soak them; you just want to add a hint of humidity back into the air.
If you notice "eyes" beginning to sprout in February or March, it usually means your storage area is a bit too warm. Move the boxes to a cooler spot to slow down their growth until it is time to plant.
Preparing for Spring
As the days grow longer and the soil begins to warm, your dahlia tubers will naturally start to wake up. This is an exciting time! About a month before your last expected frost, you can bring the boxes into a warmer room to encourage the eyes to swell. For spring planting details, see How to Plant Dahlias.
If you didn't divide your tubers in the fall, now is the time. With the eyes clearly visible as small pink or green bumps, you can easily see where to make your cuts. Each division should have a healthy eye and a firm body.
Wait to plant your tubers outdoors until the soil temperature reaches about 60°F and all danger of frost has passed. Planting too early into cold, wet soil can lead to rot before the plant even has a chance to grow. Patience is rewarded with faster growth and healthier plants once the summer sun arrives.
Simple Troubleshooting
Even with the best care, you might encounter a few challenges. Most dahlia issues during storage are related to moisture or temperature.
- If tubers feel "rubbery": This is the beginning of shriveling. It is usually caused by a storage medium that is too dry or a room with very low humidity. Mist the packing material slightly and ensure the box is not near a heater or vent.
- If the stem "handle" is moldy: This can happen if the stems weren't allowed to dry completely before packing. Trim away the moldy portion of the stem down to healthy tissue and leave the clump out in the air for a day before repacking it in fresh, dry medium.
- If the tubers have tiny holes: This could be from wireworms or other soil pests that were present before you dug them up. As long as the area around the hole is firm and not rotting, the tuber should be fine. Just keep a closer eye on it during your monthly checks.
At Longfield Gardens, we want every gardener to feel confident in their ability to keep these beautiful flowers part of their landscape year after year. By following these straightforward steps for cleaning and storing, you are setting yourself up for a spectacular garden next season. For more ordering details, see our Shipping Information.
Conclusion
Cleaning and storing dahlia tubers is a rewarding process that bridges the gap between gardening seasons. By timing your harvest with the frost, cleaning the tubers thoroughly, and providing a cool, stable winter home, you ensure your favorite varieties return with even more vigor. This simple cycle of care allows you to enjoy the spectacular beauty of dahlias year after year while growing your garden's collection.
- Wait for the frost to signal the plant to go dormant.
- Dig widely and gently to protect the fragile tuber necks.
- Clean and dry the tubers to prevent winter rot.
- Store in a cool, dark place between 40°F and 50°F.
Success with dahlias comes down to managing moisture and temperature during the "sleeping" months. With a little attention, your tubers will be ready to burst into growth as soon as the spring sun warms the soil.
We look forward to helping you grow a more beautiful garden with our premium selection of dahlias and perennials. Learn more about our promise on About Us.
FAQ
Can I leave my dahlia tubers in the ground all winter?
In USDA hardiness zones 8 and warmer, dahlia tubers can often survive the winter in the ground if the soil is well-draining and protected by a thick layer of mulch. However, in zones 7 and colder, the ground freezes deep enough to kill the tubers. For most US gardeners, digging and storing them indoors is necessary to ensure they return the following year. For more winter-care guidance, read How to Overwinter Dahlias.
Do I have to wash the tubers, or can I just brush off the dirt?
While you can simply brush off the dirt if you have very sandy soil, washing them with a hose is highly recommended. Soil can trap moisture against the skin and hide early signs of rot or pests. Washing ensures the tubers are clean and dry before they go into their packing medium, which significantly reduces the risk of fungal issues during storage.
What should I do if my tubers look shriveled in mid-winter?
If your tubers look like raisins or feel rubbery, they are losing too much moisture. This is common in homes with dry winter air. To fix this, lightly mist the storage medium (the peat moss or wood shavings) with a spray bottle of water. Do not wet the tubers directly; you only want to increase the humidity within the container to stop further dehydration.
Why did my dahlia tubers turn into mush during storage?
Mushy tubers are a sign of rot, usually caused by one of three things: the tubers were packed while still wet, they were exposed to freezing temperatures, or the storage medium was too damp. To prevent this, ensure tubers are dry to the touch before packing, keep them in a spot that stays above 40°F, and always remove any soft tubers immediately to prevent the rot from spreading.
