Introduction
Growing dahlias is one of the most rewarding experiences a gardener can have. There is a unique thrill in watching a small, potato-like tuber transform into a towering plant topped with intricate, colorful blooms that last from midsummer until the first frost. These spectacular flowers often become the centerpiece of the landscape, providing endless bouquets for your home. At Longfield Gardens, we believe that the joy of dahlias shouldn't end when the temperature drops.
By learning how to harvest and store your dahlia tubers, you can preserve your favorite varieties and enjoy them again next season. This process is a simple way to expand your garden and ensure your most beloved plants return even stronger. Whether you are a first-time grower or looking to refine your technique, this guide will walk you through the essential steps to keep your tubers safe and healthy through the winter months, and explore new dahlias for next season.
Harvesting and storing dahlias is a straightforward project that rewards a little bit of autumn effort with a lifetime of beautiful summer color.
Understanding the Dahlia Life Cycle
Before you grab your shovel, it helps to understand what is happening beneath the soil. Dahlias are tender perennials. In warm climates (typically USDA hardiness zones 8 and warmer), they can often stay in the ground year-round. However, in most of the United States, the cold winter soil will cause the tubers to freeze and rot.
A dahlia tuber is a tuberous root. Its job is to store energy and water for the plant to use when it wakes up in the spring. Throughout the summer, the "mother tuber" you planted in the spring grows a cluster of new tubers. By autumn, a single plant can produce a large clump of five to twenty new tubers. Harvesting these clumps allows you to protect that stored energy and even multiply your plant collection.
When to Harvest Your Dahlias
Timing is one of the most important factors in successful dahlia storage. If you dig too early, the tubers may not be fully mature or "cured," making them more likely to shrivel in storage. If you wait too long, a deep freeze could damage the tubers.
The Signal of the First Frost
For most gardeners, the first "killing frost" is the perfect signal. You will know it has happened when your vibrant dahlia plants suddenly turn dark brown or black overnight. While the sight of a frozen plant might seem sad, this is actually a helpful part of the process. The frost tells the plant to stop sending energy to the leaves and start concentrating it in the tubers.
The Waiting Period
Once the foliage has died back after a frost, we recommend waiting about one to two weeks before digging. This short rest period in the soil allows the tubers to develop a slightly tougher skin, which helps them stay hydrated during the winter. It also encourages the "eyes"—the small bumps where next year’s sprouts will emerge—to become more visible.
If you live in an area where a killing frost doesn't arrive until very late in the year, you can still harvest your tubers. Simply wait until the foliage begins to yellow and die back naturally in late October or early November.
Key Takeaway: The ideal time to harvest is 7 to 14 days after the first killing frost has turned the foliage brown.
Preparing the Plants for Digging
Before you start lifting tubers, you need to clear away the summer growth. This makes the job much easier and helps you keep track of your different varieties.
- Cut the Stems: Use a sharp pair of loppers or hand pruners to cut the main stalks down to about 4 to 6 inches above the ground. These short stems will act as "handles" during the digging process, but be careful not to pull on them too hard.
- Label Immediately: Dahlias all look very similar once they are out of the ground. Before you move on to the next plant, attach a waterproof label to the stem handle or write the variety name directly on a tuber with a permanent marker.
- Clear the Area: Move the discarded foliage to your compost pile or garden waste bin. This gives you a clear workspace around the base of the plant.
How to Dig Dahlia Tubers Safely
Dahlia tubers are surprisingly fragile. They are connected to the main stem by thin "necks." If these necks are broken or severely creased, the tuber may not be able to sprout next year. The goal is to lift the entire clump as one sturdy unit.
Choose the Right Tools
A garden fork (sometimes called a digging fork or pitchfork) is generally better than a shovel. The tines of a fork allow you to loosen the soil without creating a solid "slice" that might cut through a tuber. If you only have a shovel, just be extra cautious with your spacing.
The Lifting Technique
Start by inserting your fork into the soil about 12 inches away from the center of the stalk. Digging too close is the most common way to accidentally damage a tuber.
- Circle the plant, loosening the soil on all sides.
- Gently pry upward from different angles to break the suction of the soil.
- Once the clump feels loose, place your hand under the clump and lift it out.
- Avoid pulling the clump up by the stem, as the weight of the soil can snap the tubers off the neck.
What to do next:
- Gently shake off the largest clumps of loose soil.
- Check for any damaged or "mushy" tubers and remove them.
- Keep the variety label securely attached to the clump.
Cleaning and Curing the Tubers
Once the tubers are out of the ground, they need a little preparation before they go into long-term storage.
Washing vs. Brushing
There are two schools of thought on cleaning. Some gardeners prefer to wash their tubers thoroughly with a garden hose to remove all soil. This makes it easier to spot "eyes" and check for rot. Others prefer to let the soil dry and then gently brush it off.
If you have heavy clay soil, washing is usually the best option. If you have light, sandy soil, a simple brushing may be enough. If you do wash your tubers, be very gentle with the water pressure to avoid nicking the skin.
The Curing Process
Curing is simply letting the tubers dry out slightly in a protected environment. This "sets" the skin and helps prevent fungal issues.
- Place the tubers in a cool, shaded area with good air circulation (like a garage, shed, or covered porch).
- Avoid direct sunlight, which can cause the tubers to overheat or dry out too quickly.
- Turn the clumps upside down so that any water trapped in the hollow stems can drain out.
- Let them cure for 2 to 4 days until the skin feels dry and the remaining soil is easy to brush away.
To Divide or Not to Divide?
One of the most common questions we receive is whether to divide the tuber clumps in the fall or the spring. Both methods work well, and the choice depends on your preference and available space.
Dividing in the Fall
Some gardeners like to divide their tubers immediately after harvesting. This takes up much less storage space and allows you to see the health of each individual tuber. However, the "eyes" can be very difficult to see in the fall. If you divide in the fall, you must ensure each piece has a portion of the "crown" (the area where the tuber meets the stem) and at least one viable eye.
Dividing in the Spring
We often recommend that beginners wait until spring to divide. After a few months of storage, the eyes will often start to swell or even sprout, making it much easier to see exactly where to cut. Storing the clumps whole also provides a bit of a safety net; if one part of the clump struggles, the rest is often still healthy.
The Ideal Storage Environment
Dahlias are like Goldilocks—they don't want to be too cold, too warm, too wet, or too dry. For a step-by-step refresher, see How to Overwinter Dahlias. Finding the "just right" spot is the secret to high success rates.
The Perfect Temperature
The goal is to keep the tubers dormant without letting them freeze. The ideal temperature range is between 40°F and 50°F (4°C to 10°C).
- Too cold: If the temperature drops below 32°F, the water inside the tubers will freeze, turning them into mush.
- Too warm: If the area is consistently above 55°F, the tubers may think it is spring and start to sprout prematurely, or they may dry out too quickly.
Unheated basements, crawl spaces, or insulated garages are often perfect spots.
Humidity and Moisture
Tubers need a certain amount of humidity to stay plump, but they need to stay dry enough to prevent mold. Aim for about 80% to 90% humidity in the storage container itself.
Choosing a Storage Medium
Storing tubers in a "packing medium" helps regulate moisture and provides insulation. Popular choices include:
- Vermiculite: This is many gardeners' top choice because it holds onto a tiny bit of moisture while still allowing for air circulation.
- Wood Shavings: Pine or cedar shavings (the kind used for pet bedding) are inexpensive and effective.
- Peat Moss: This is a classic choice, though it can sometimes be a bit dusty to work with.
- Newspaper: Some gardeners find success simply wrapping individual tubers or clumps in several layers of dry newspaper.
Step-by-Step Storage Methods
There are several ways to pack your dahlias for the winter. For shipping details, see our Shipping Information. Here are two of the most reliable methods:
Method 1: The Crate or Box Method
This is best for whole clumps or large collections.
- Line a plastic milk crate or a sturdy cardboard box with several layers of newspaper or a large paper bag.
- Add a 2-inch layer of your chosen storage medium (vermiculite or wood shavings) to the bottom.
- Place the dahlia clumps in the box. It is okay if they touch slightly, but try to keep them in a single layer if possible.
- Cover the tubers completely with more storage medium.
- Keep the top of the box or crate slightly open to allow for some air exchange.
Method 2: The Plastic Bag Method
This is a great space-saving option for divided tubers or for gardeners with very dry storage areas.
- Place a few handfuls of slightly damp (not wet!) vermiculite or peat moss into a gallon-sized plastic bag.
- Add a few tubers to the bag, making sure they are surrounded by the medium.
- Do not zip the bag completely shut. Leave a one-inch gap for air to escape. This prevents the "greenhouse effect" from causing rot.
Key Takeaway: Whatever method you choose, the goal is to keep the tubers cool, dark, and slightly hydrated without allowing standing water to sit on the skins.
Winter Monitoring and Maintenance
Successful storage isn't just about "set it and forget it." Checking on your tubers once a month during the winter can save your entire collection.
What to Look For
- Shriveling: If the tubers look very wrinkled or feel soft like a sponge, they are losing too much moisture. Lightly mist the storage medium with water to increase the humidity.
- Rot or Mold: If you see fuzzy white mold or black, mushy spots, the area is too damp. Remove the affected tubers immediately so the rot doesn't spread. If the rot is only on a small tip, you can often cut it off with a clean knife and let the cut air-dry.
- Sprouting: If you see green sprouts in January, your storage area is likely too warm. Move the containers to a cooler spot to slow down their growth.
Troubleshooting Common Issues
Even with the best care, you might encounter a few challenges. Here is how to handle the most common storage questions.
My Tubers Look Like Raisins
Don't panic! A little bit of wrinkling is normal as the tubers lose a small amount of moisture over the winter. As long as they are still firm when you squeeze them, they are perfectly viable. If they are very shriveled, a quick soak in room-temperature water for an hour before planting in the spring will usually wake them up.
I Found a Rotten Tuber
Rot happens occasionally, usually due to a nick during digging or a spot that stayed too wet. If you catch it early, it isn't a problem. Simply discard the rotten tuber. If the rot is on a clump, you can often "perform surgery" by cutting away the bad part until you see clean, white flesh.
My Storage Area Froze
If you suspect your tubers have frozen, wait for them to thaw and then give them a squeeze. If they feel like a bag of liquid or turn into a dark, slimy mess, they unfortunately cannot be saved. This is why a thermometer in your storage area is a great investment for peace of mind.
Planning for Spring
As the days get longer in March and April, it’s time to start thinking about the new growing season. About 4 to 6 weeks before your last expected frost, you can bring your dahlia tubers out of storage. This is the perfect time to divide clumps if you didn't do it in the fall.
You can "pre-start" your dahlias in pots indoors if you want earlier blooms, or simply wait until the soil is warm (at least 60°F) to plant them directly in the garden. Each healthy tuber with an eye is a brand-new plant ready to fill your yard with color.
What to do next:
- Keep a garden journal of which varieties stored best in your specific conditions.
- Sanitize your cutting tools with a 10% bleach solution between different varieties to keep your stock healthy.
- Start browsing for new colors to add to your collection next season.
Conclusion
Harvesting and storing dahlia tubers is a rewarding ritual that marks the end of one beautiful season and the promise of the next. It’s a simple process of working with nature: letting the frost signal the end of growth, gently lifting the energy-packed tubers, and providing a cool, quiet place for them to rest. While it might seem like a lot of steps at first, most gardeners find that it quickly becomes a favorite part of the autumn routine.
At Longfield Gardens, we want every gardener to feel confident that their investment in beauty will last for years to come. By following these basic rules of timing, gentle handling, and proper temperature control, you can ensure that your dahlias return to provide spectacular color and joy summer after summer.
Harvesting your own tubers is the most satisfying way to grow your garden and share the beauty of dahlias with friends and neighbors.
As you tuck your tubers away for their winter nap, you can look forward to the excitement of seeing those first green shoots emerge next spring, starting the cycle of beauty all over again.
FAQ
When is the best time to dig up my dahlia tubers?
The best time is usually about one to two weeks after the first killing frost has turned the foliage brown. This waiting period allows the tubers to "cure" in the ground and helps the eyes become more visible. If you don't get a hard frost in your area, aim to harvest in late October or early November when the plants naturally begin to fade.
Can I leave my dahlias in the ground over the winter?
This depends entirely on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlias in the ground, though it is still a good idea to cover them with a thick layer of mulch to protect the crowns from excess moisture and light freezes. In Zones 7 and colder, the ground will freeze deep enough to kill the tubers, so harvesting and storing them indoors is necessary.
What should I do if my tubers look shriveled in the middle of winter?
If your tubers look very wrinkled or feel soft, they are likely too dry. You can fix this by lightly misting the storage medium (like the vermiculite or wood shavings) with a spray bottle of water. Avoid soaking them, as too much water can cause rot; you just want to raise the humidity enough to stop the shriveling.
How can I tell if a tuber is still good to plant in the spring?
A healthy tuber should feel firm, similar to a fresh potato. It should not be mushy, oozing, or smell foul. Look for the "eye," which is a small bump or sprout near the neck of the tuber. As long as the tuber is firm and has a viable eye, it will grow into a beautiful new plant. For a closer look at tuber anatomy and what to expect, see Dahlia Tubers: What You Need to Know.
