When and How to Dig Up Dahlia Bulbs

Table of Contents

1. Introduction
2. When to Dig Up Dahlia Bulbs
3. Preparing the Plants for Digging
4. How to Dig Up Dahlia Tubers Correctly
5. Cleaning and Curing the Tubers
6. Dividing Dahlia Tubers: Fall vs. Spring
7. Winter Storage Techniques
8. Monitoring Your Tubers Through Winter
9. Replanting in the Spring
10. Common Myths About Digging Dahlias
11. Summary of Success
12. FAQ
13. Conclusion

Introduction

There is a unique sense of accomplishment that comes with a successful dahlia season. These spectacular plants are often the crowning glory of the summer garden, offering a dizzying array of colors and shapes that last from midsummer right up until the first cold snap. At Longfield Gardens, we believe the only thing better than enjoying a dahlia bloom today is knowing you can enjoy that same beauty again next year.

Because dahlias are tropical plants native to warmer climates, they cannot survive freezing winter temperatures in most parts of the United States. To keep your favorite varieties safe, you simply need to lift the tubers from the ground and store them in a protected spot until spring. While this process might seem technical to a new gardener, it is actually quite straightforward once you understand the rhythm of the plant.

This guide will walk you through the ideal timing for lifting your dahlias, the best tools for the job, and how to keep those tubers healthy and plump through the winter months. By following a few simple steps, you can turn a one-season display into a lifelong collection of beautiful flowers. For a little inspiration, browse our Dinnerplate dahlias.

When to Dig Up Dahlia Bulbs

Determining the right time to lift your dahlias is mostly about watching the weather and the behavior of the plant. In most regions, the signal to start digging is the arrival of the first "killing frost." This is the frost that turns the lush green foliage black or dark brown overnight.

While it is tempting to start digging as soon as the weather turns chilly, waiting for this frost is beneficial. The sudden drop in temperature signals the plant to go into dormancy, shifting its energy from flower production down into the tubers. This helps the tubers mature and prepares them for their long winter nap.

The Benefit of Waiting

Many experienced gardeners like to wait about a week after the first frost before they actually start digging. During this week, the "eyes" on the tubers—the small bumps where next year’s growth will emerge—often become more prominent and easier to see.

If you live in a region where a killing frost doesn't arrive until very late in the year, or if your soil stays excessively wet in the fall, you don't have to wait for the frost. You can safely dig your tubers in late October or early November. The most important rule is to get the tubers out of the ground before the soil itself freezes solid.

Managing Different Climates

If you are gardening in USDA hardiness zones 8 through 11, you may be able to leave your dahlias in the ground all year. In these warmer areas, the ground rarely freezes deep enough to damage the tubers. However, even in warm zones, many gardeners choose to dig and divide their dahlias every couple of years to prevent the clumps from becoming overcrowded, which can lead to smaller blooms and weaker stems.

For those of us in zones 3 through 7, digging is a necessary annual ritual. If an early freeze is predicted and you haven't had a light frost yet, it is perfectly fine to move your timeline up. It is always better to dig a few days early than to let the tubers sit in frozen, soggy soil. Use our Hardiness Zone Map to confirm your zone.

Key Takeaway: The best time to dig is generally 3 to 7 days after the first killing frost has turned the foliage black. Always ensure the tubers are out of the ground before the soil freezes.

Preparing the Plants for Digging

Before you reach for your shovel, you need to clear away the summer's growth. This makes the lifting process much cleaner and helps you see exactly where the crown of the plant is located.

Cutting Back the Stems

Start by cutting the dahlia stems down to about 4 to 6 inches above the soil line. You can use sharp pruners, loppers, or even a small hand saw for particularly thick, woody stems. Leaving a short "handle" of the stem is very helpful. It gives you a way to steady the clump as you lift it, and it provides a place to attach a label so you don't forget which variety is which.

Sanitizing Your Tools

One of the most important habits to develop is sanitizing your cutting tools between different plants. Dahlias can sometimes carry viruses or bacteria that aren't immediately visible. By dipping your pruners in a solution of one part bleach to ten parts water (or using a disinfectant spray) between each plant, you ensure that you aren't accidentally spreading issues from one tuber clump to another.

Labeling Your Varieties

Once the flowers are gone and the stems are cut, dahlia tubers all look very similar. To ensure your garden layout stays organized next spring, label each plant as you cut it back. You can use waterproof nursery tags, or even write the name of the variety directly on the tuber with a permanent marker once it is clean.

What to do next:

• Gather your loppers and a bucket of disinfectant.
• Cut all stems down to about 5 inches.
• Double-check that your labels are securely attached to the remaining stem "handles."

How to Dig Up Dahlia Tubers Correctly

Dahlia tubers grow in a circular clump just beneath the soil surface. They are joined at a central point called the "crown," and the "necks" of the individual tubers are quite fragile. If a tuber snaps off without a piece of the crown attached, it will not grow next year. This is why a gentle hand is essential during the lifting process.

Choose the Right Tool

A garden fork (or pitchfork) is generally the best tool for this job. The tines allow you to loosen the soil and lift the clump without the suction and resistance you often get with a solid shovel. If you only have a shovel, just be extra careful to dig a wide circle around the plant.

The Lifting Process

To avoid damaging the tubers, start your digging about 10 to 12 inches away from the main stem. Insert your fork deep into the ground and gently pry upward. Work your way around the entire plant in a circle, loosening the soil from all sides.

Once the soil is loose, place one hand on the stem handle and use the fork to gently lever the clump out of the ground. Resist the urge to yank the plant upward by the stem; instead, use the stem only to guide the clump as the fork does the heavy lifting.

Initial Cleaning

Gently shake the clump to remove large clods of soil. If your soil is dry and sandy, most of it will fall away easily. If you have heavy clay soil, it may cling to the tubers. Don't worry about getting them perfectly clean just yet. At this stage, your goal is simply to get the clump out of the ground intact.

Key Takeaway: Dig a wide circle at least 12 inches from the stem to avoid slicing through the tubers. Use a garden fork to gently pry the clump upward rather than pulling on the stem.

Cleaning and Curing the Tubers

Once the tubers are out of the garden, they need a little bit of preparation before they are ready for storage. For a closer look at what makes a tuber viable, see Dahlia Tubers: What You Need to Know.

To Wash or Not to Wash?

Gardeners have different opinions on washing tubers. At Longfield Gardens, we find that a middle-ground approach works best.

If your soil is light and loose, you can simply brush off the excess dirt with your hands or a soft brush. If your soil is heavy clay, it is often better to wash the tubers with a gentle stream from a garden hose. Removing thick clay makes it much easier to inspect the tubers for damage and to find the "eyes" if you plan on dividing the clumps.

If you do wash your tubers, it is vital that they dry completely before you pack them away. Moisture trapped against the skin in a storage box is the primary cause of winter rot.

Trimming and Inspection

After the tubers are relatively clean, take a close look at the clump.

1. Remove the "Mother" Tuber: This is the original tuber you planted in the spring. It is often larger, darker, and may look slightly shriveled or have a different texture. It has done its job and is prone to rotting over the winter, so it is best to prune it away.
2. Trim Fine Roots: Use clean scissors or pruners to snip off any long, hair-like feeder roots.
3. Check for Damage: If a tuber was accidentally sliced by the shovel or has a broken neck, it is best to remove it now.

The Curing Process

Place your cleaned and trimmed tubers in a frost-free area with good air circulation, such as a garage, shed, or a covered porch. Keep them out of direct sunlight, as the sun can dry them out too quickly and cause shriveling.

Let the tubers sit for 1 to 3 days. During this time, the "skin" will dry and firm up. If you washed them, ensure all the nooks and crannies where the tubers meet the crown are dry to the touch before proceeding to the final storage step.

Dividing Dahlia Tubers: Fall vs. Spring

One of the most common questions we receive is whether you should divide your dahlia clumps into individual tubers in the fall or wait until the spring. Both methods have advantages.

Dividing in the Fall

The primary benefit of dividing in the fall is that the tubers are softer and easier to cut. Additionally, divided tubers take up much less space in storage than whole clumps. However, the "eyes" (the growth points) can be very difficult to see in the fall. If you cut a tuber and miss the eye, that tuber will never sprout.

Dividing in the Spring

Many home gardeners find it much easier to store the entire clump whole and divide it in the spring. By March or April, the eyes will often begin to swell or even sprout slightly, making it obvious where you should make your cuts. For planting basics, see How to Plant Dahlias.

If this is your first time saving dahlias, we recommend storing the clumps whole. It is the safest way to ensure you don't accidentally throw away viable tubers.

Winter Storage Techniques

The goal of winter storage is to keep the tubers in a "Goldilocks" environment: not too cold (they shouldn't freeze), not too warm (they shouldn't sprout), and not too dry (they shouldn't shrivel).

The Ideal Conditions

The perfect temperature for dahlia storage is between 40°F and 45°F. For most people, an unheated basement, a crawl space, or an insulated garage that stays above freezing is the best location.

Humidity is also a factor. You want the air to be somewhat humid (around 80%) so the tubers stay plump, but you need enough air circulation to prevent mold.

Choosing a Storage Medium

You should never store tubers "naked" in a box, as they will dry out. Instead, pack them in a material that helps regulate moisture. Popular choices include:

• Coarse Vermiculite: This is many gardeners' favorite choice because it is sterile and does a great job of holding just the right amount of moisture.
• Pine Shavings: Often sold as animal bedding, these are inexpensive and provide good insulation.
• Peat Moss: This is a classic choice, though it can sometimes be a bit too dry, so you may need to check it periodically.

Packing the Tubers

Choose a container that allows for some breathability, such as a cardboard box or a plastic bin with a few holes drilled in the sides.

1. Place a 2-inch layer of your chosen medium in the bottom of the container.
2. Lay your tubers or clumps on top, making sure they aren't touching each other.
3. Cover them completely with more medium.
4. If you have a lot of tubers, you can create multiple layers, as long as there is medium between them.

Key Takeaway: Store tubers at 40-45°F in a breathable container filled with vermiculite or pine shavings. Check them once a month to ensure they aren't rotting or shriveling.

Monitoring Your Tubers Through Winter

Saving dahlias isn't a "set it and forget it" task. It is a good idea to check on your storage boxes once a month throughout the winter.

What to Look For

When you check your tubers, you are looking for two things: rot and shriveling.

• If you see rot: If a tuber feels mushy or has visible mold, remove it immediately and throw it away. Rot can spread quickly through a box, so removing the "bad apple" is essential to saving the rest.
• If you see shriveling: If the tubers look wrinkled like a raisin, they are losing too much moisture. Lightly mist the storage medium with a spray bottle of water. You don't want it to be wet, just slightly damp to the touch.

Addressing Early Sprouting

If you notice your dahlias are starting to grow long green sprouts in January or February, your storage area is likely too warm. Move the boxes to a cooler spot. You can gently snap off these early sprouts; the tuber has plenty of energy to push out new ones when you plant it in the spring.

Winter Checklist:

• Check tubers once every 30 days.
• Remove any soft or moldy pieces.
• Mist the medium if tubers appear wrinkled.
• Adjust the location if temperatures fluctuate too much.

Replanting in the Spring

As the days grow longer and the danger of frost passes, it will be time to bring your dahlias back out into the light. Usually, this happens in late April or May, depending on your local climate.

Before planting, take the tubers out of their boxes and give them a final inspection. They should feel firm, like a fresh potato. If you stored your clumps whole, this is the perfect time to divide them. Look for the small bumps (eyes) near the neck of the tuber and use a sharp, sanitized knife to separate them, ensuring each piece has at least one eye and a solid tuber attached.

For an early start, many gardeners like to "wake up" their tubers by potting them up indoors about 4 to 6 weeks before the last frost date. This gives the plants a head start, leading to earlier blooms in the summer.

Common Myths About Digging Dahlias

In the world of gardening, there is a lot of conflicting advice. Let's clear up a few common misconceptions about digging and storing dahlia bulbs.

"You must wash them with bleach"

While you should sanitize your tools with bleach, you should not soak the tubers themselves in a heavy bleach solution. A gentle rinse with plain water is all that is needed to remove soil. If you are worried about fungus, some gardeners use a light dusting of sulfur powder, but for most home gardens, proper drying (curing) is the best preventative measure against rot.

"They will die if you don't dig them immediately after frost"

While you don't want to leave them in the ground until it freezes solid, the tubers are actually quite safe in the soil for a week or two after the foliage dies. In fact, that short "rest" in the ground can help the eyes become more visible. There is no need to panic and dig them in the dark during a frost event!

"Big tubers are better"

Surprisingly, huge dahlia tubers aren't always the best performers. Medium-sized, firm tubers often sprout faster and create more vigorous plants than giant, woody ones. Don't be discouraged if your clumps produce a variety of sizes; as long as there is an eye and a healthy neck, they will grow.

Summary of Success

Digging and storing dahlias is a rewarding extension of the gardening season. It connects you to the lifecycle of your plants and allows you to build a garden that grows more beautiful every year. By getting the timing right, handling the tubers with care, and providing a cool, stable winter home, you are ensuring a spectacular floral display for the seasons to come.

We at Longfield Gardens are proud to support you in this journey. Whether you are growing a single "Dinnerplate" dahlia in a container or a whole row of "Cactus" types for cutting, the effort you put into saving your tubers now will be repaid ten-fold when those first buds open next summer. If you want a closer look at the different forms available, explore our Cactus dahlias.

"Saving your dahlia tubers is like putting your garden in a time capsule. With a little bit of care in the fall, you can unlock the exact same colors and joy year after year."

FAQ

Can I leave my dahlias in the ground if I mulch them heavily?

In zones 7b and warmer, a thick layer of mulch (6-10 inches) might protect dahlia tubers through the winter. However, in colder zones, the frost will penetrate the soil regardless of mulch, turning the tubers to mush. For most US gardeners, digging is the only reliable way to keep them alive. If you want to compare options for next season, browse our dahlia bulbs.

What happens if I accidentally cut a tuber while digging?

If you slice a tuber but the rest of the clump is intact, simply prune away the damaged tuber. If the cut is on a tuber you want to save, let it dry thoroughly so the wound "callouses" over. As long as the neck and crown are undamaged, the tuber may still be viable, but keep an eye on it for rot.

Do I need to store my dahlias in the dark?

Yes, it is best to store them in a dark or dimly lit area. Light can encourage the tubers to sprout prematurely or, in some cases, can cause the tubers to turn green and tough. A dark basement or a closed box is the ideal environment.

Why did my stored tubers turn into "mush" by spring?

This is almost always caused by too much moisture or freezing temperatures. If the tubers weren't fully dry before being packed, or if the storage medium stayed wet, rot will set in. Conversely, if the temperature dropped below 32°F in your storage area, the water inside the tubers froze, destroying the cell walls and leaving them mushy when they thawed. For a broader look at dahlia varieties, start with our main dahlia collection.

Conclusion

Digging and storing your dahlia tubers is one of the most practical and satisfying skills a gardener can master. It transforms a seasonal flower into a long-term investment, allowing you to preserve the specific varieties you love most. By following the natural cues of the first frost and treating the fragile tubers with a gentle touch, you can ensure a high success rate. If you are planning ahead for spring, our dahlia collection is a helpful place to start.

• Wait for the first frost to signal dormancy.
• Dig a wide circle with a garden fork to protect the tubers.
• Cure the tubers for a few days before packing them away.
• Store in a cool, frost-free place in a medium like vermiculite.

At Longfield Gardens, we want to help you make your garden as vibrant and successful as possible. Saving your tubers is an easy win that brings the excitement of spring to the middle of autumn. For more tips on plant care or to find new varieties to add to your collection next year, we invite you to explore our other guides and Managing Dahlias for Maximum Blooms. Happy gardening!