Do You Dig Up Dahlia Bulbs in the Fall?

Table of Contents

1. Introduction
2. Understanding Your Climate: To Dig or Not to Dig?
3. When Is the Best Time to Dig?
4. Essential Tools for the Harvest
5. How to Dig Up Dahlia Tubers: Step-by-Step
6. Cleaning and Curing Your Tubers
7. Winter Storage Strategies
8. Dividing Your Dahlias: Fall or Spring?
9. Troubleshooting Common Winter Issues
10. Preparing for Spring Replanting
11. Conclusion
12. FAQ

Introduction

There is nothing quite like the late-summer glory of a dahlia garden. These plants are the undisputed stars of the season, producing a non-stop parade of colors and shapes that last right up until the weather turns crisp. After enjoying months of spectacular blooms, it is only natural to want to save that beauty for next year. At Longfield Gardens, we believe that gardening should be a rewarding cycle of growth, and saving your favorite varieties is one of the most satisfying ways to build a garden that gets better every single year.

This guide is designed for home gardeners who want to know exactly what to do with their dahlias once the summer heat fades. We will cover how to determine if your climate requires you to lift your tubers, the best timing for the "big dig," and how to store them so they stay healthy until spring. Whether you are a first-time dahlia grower or looking to refine your technique, we are here to help you succeed.

Digging up dahlia tubers is a simple and effective way to protect your investment and ensure a vibrant, bloom-filled landscape for many seasons to come.

Understanding Your Climate: To Dig or Not to Dig?

The most common question we hear as the season winds down is whether digging is actually necessary. The answer depends almost entirely on where you live. Dahlias are native to the warm mountain regions of Mexico and Central America. Because they evolved in a climate that doesn’t experience deep freezes, they have not developed the ability to survive in frozen soil.

In the gardening world, we use USDA Hardiness Zones to determine which plants can survive the winter outdoors. For dahlias, the "magic number" is usually Zone 8. If you live in Zone 8, 9, 10, or 11, your soil likely stays warm enough that your dahlias can remain in the ground year-round. In these warmer regions, the tubers enter a period of dormancy but do not freeze. You can simply cut the foliage back and perhaps add a layer of mulch for extra protection.

However, if you live in Zone 7 or colder, the ground will likely freeze deep enough to reach the tubers. When dahlia tubers freeze, the water inside their cells expands and bursts, turning the once-firm tuber into mush. For most gardeners in the United States—especially those in the Northeast, Midwest, and mountain regions—digging them up is a necessary part of the fall routine.

Key Takeaway: If your winters involve frozen ground (USDA Zone 7 and below), you should dig up your dahlia tubers to keep them safe for next year.

When Is the Best Time to Dig?

Timing is everything when it comes to harvesting dahlias. If you dig too early, the tubers may not have stored enough energy to survive the winter. If you wait too long, you risk a deep freeze that could damage the tubers before you get them out of the ground.

The Frost Signal

The best indicator that it is time to dig is your local weather. We recommend waiting until a killing frost has hit your garden. You will know this has happened when the lush green foliage of your dahlias turns black or dark brown overnight. While it might look a little sad to see your vibrant plants go dormant, this is actually a helpful signal from nature.

When the top of the plant dies back from a light frost, it tells the tuber below the ground to stop growing and start "curing." The plant shifts its remaining energy into the tubers, helping them toughen up for their winter nap.

The Two-Week Rule

If your schedule allows, the best practice is to cut the blackened stalks down to about 4 to 6 inches above the soil and then wait about 10 to 14 days before digging. This short waiting period allows the tubers to develop a slightly thicker "skin." This process, often called curing, helps the tubers retain moisture during winter storage.

Of course, weather can be unpredictable. If the forecast calls for a sustained deep freeze where the ground might freeze solid, it is perfectly fine to dig them up right after the first frost.

Action Steps for Timing

• Monitor your local weather for the first "killing frost."
• Wait for the foliage to turn black or dark brown.
• Cut the stems down to a 6-inch "handle."
• If possible, let the tubers rest in the ground for a week to toughen up.
• Dig before the ground itself freezes solid.

Essential Tools for the Harvest

You don't need a shed full of specialized equipment to dig up your dahlias, but having the right tools on hand will make the job much easier and help prevent damage to the tubers.

1. A Garden Fork (Pitchfork): This is our top recommendation. A garden fork allows you to lift the soil and the tuber clump from underneath without the high risk of slicing through a tuber that a flat shovel carries.
2. Sturdy Pruners or Loppers: Dahlia stems can become quite thick and woody by the end of summer. A good pair of bypass pruners or loppers will help you cut through the stalks cleanly.
3. Garden Gloves: Digging is a hands-on job, and a pair of waterproof or heavy-duty gloves will keep your hands dry and protected.
4. Labeling Materials: This is the most overlooked tool! Once tubers are out of the ground, they all look very similar. Have waterproof tags or a garden marker ready to identify each variety.
5. A Soft Brush: A simple paintbrush or a soft-bristled handheld brush is useful for removing excess soil without scratching the tuber's skin.

How to Dig Up Dahlia Tubers: Step-by-Step

Digging up dahlias is a straightforward process, but it requires a gentle touch. Unlike potatoes, which are quite rugged, dahlia tubers are connected to the main stem by a narrow "neck." If this neck is broken or cracked, the tuber will not be able to sprout next year.

Step 1: Clear the Area

Start by cutting the stalks down if you haven't already. Leave about 4 to 6 inches of stem protruding from the ground. This serves as a "handle" that helps you see exactly where the center of the plant is, but remember: never use this handle to pull the plant out of the soil.

Step 2: Dig Wide

The tuber clump underground is often much wider than the stem above. To avoid hitting the tubers with your fork, start digging at least 12 inches away from the stem. Sink your garden fork deep into the soil all the way around the plant. You are looking to loosen the soil in a wide circle.

Step 3: Lift Gently

Once you have loosened the soil around the entire perimeter, gently pry upward with your garden fork. You want to lift the entire clump from underneath. As the soil begins to heave, you can use one hand to steady the "stem handle" while the fork does the heavy lifting. The goal is for the clump to pop out of the ground as one whole unit.

Step 4: Shake Off Excess Soil

Once the clump is out, give it a gentle shake to remove the largest chunks of soil. Do not bang the tubers against each other or against the ground, as this can bruise them or break the delicate necks.

Key Takeaway: Always dig much wider than the stem and lift from underneath. The "neck" of the tuber is its most fragile point and must remain intact for future growth.

Cleaning and Curing Your Tubers

Once your tubers are out of the ground, they need a little bit of preparation before they go into storage. There is some debate in the gardening community about whether to wash tubers with a hose or simply brush the dirt off.

To Wash or Not to Wash?

At Longfield Gardens, we generally suggest a middle-ground approach. If you have very sandy soil, a simple brushing is often enough. If you have heavy clay soil that sticks to the tubers like glue, a gentle rinse with a garden hose can be helpful. Washing makes it easier to inspect the tubers for any signs of rot or damage.

However, if you do wash them, you must ensure they are 100% dry before they go into a storage box. Moisture is the primary cause of rot during the winter.

Inspection

Check each clump for:

• Soft Spots: If a tuber feels squishy or looks rotten, trim that specific tuber away from the clump using a clean, sharp knife.
• Broken Necks: If a tuber is dangling by a thread or the neck is clearly snapped, it likely won't grow. You can remove these to save space.
• "Mother" Tubers: The original tuber you planted in the spring is often identifiable as the largest, darkest, and sometimes slightly shriveled one in the center. Some gardeners choose to remove this "mother" tuber, as it is more prone to rot over the winter than the new, fresh tubers grown during the summer.

The Final Dry

Place your cleaned tubers in a frost-free, shaded area with good air circulation—like a garage or a covered porch—for 1 to 3 days. This allows any remaining surface moisture to evaporate and helps the skin continue to toughen up. Do not leave them in direct sunlight, as this can cause them to shrivel too quickly.

Winter Storage Strategies

The goal of winter storage is to keep the tubers "sleeping" but hydrated. You want a spot that is cool, dark, and slightly humid, but not wet.

The Ideal Environment

• Temperature: Between 40°F and 50°F is the sweet spot. A cool basement, an insulated crawlspace, or a corner of a garage that stays above freezing are all excellent choices.
• Airflow: While the tubers shouldn't be exposed to drying drafts, they do need a little bit of air so they don't become moldy.

Storage Containers and Media

You should never store dahlias in airtight plastic containers. Instead, use cardboard boxes, paper bags, or plastic crates with ventilation holes. To keep the tubers from drying out completely, we recommend packing them in a "medium" that regulates moisture.

Excellent storage mediums include:

• Peat Moss: Slightly dampened peat moss is a classic choice.
• Vermiculite: This holds moisture well and is very lightweight.
• Wood Shavings: Often sold as pet bedding, these are inexpensive and effective.
• Pine Bark: A fine-textured mulch can also work.

Layer the medium in the bottom of your box, nestle the tubers inside so they aren't touching each other, and then cover them with more medium. This prevents a single rotten tuber from "infecting" its neighbors.

Label Everything

Before you close the box, make sure each variety is labeled. You can write the name directly on the tuber with a soft pencil or a garden marker, or tie a tag around the stem. You will be very glad you did this come springtime!

Dividing Your Dahlias: Fall or Spring?

When you dig up a dahlia, you will notice that the single tuber you planted in the spring has multiplied into a large clump of several tubers. To get more plants for next year, you can divide these clumps into individual pieces.

The big question is when to do it.

Fall Dividing

Some gardeners prefer to divide in the fall because the tubers are softer and easier to cut. It also saves storage space because you aren't storing the bulky "core" of the clump. However, it can be very difficult to see the "eyes" (the small bumps where next year's growth will come from) in the fall.

Spring Dividing

For beginners, we highly recommend waiting until spring to divide. After a winter in storage, the tubers will begin to wake up, and the eyes will become much more visible. They look like tiny pimples or sprouts near the top of the tuber neck. If you wait until spring, you can be 100% sure that every piece you plant has a viable eye.

Simple Rules for Dividing

• Each division must have a piece of the "crown" (the part where the stem meets the tubers).
• Each division must have at least one visible "eye."
• Use a clean, sharp knife and sanitize it between different varieties to prevent the spread of disease.

Troubleshooting Common Winter Issues

Even with the best care, winter storage can sometimes present challenges. The best way to ensure success is to check on your tubers once a month during the winter.

If They Look Shrivelled

If the tubers look like a wrinkled raisin, they are losing too much moisture. This usually happens if the storage medium is too dry or the air is too arid. Give the packing material a light misting with water from a spray bottle. You don't want it wet—just slightly damp to the touch.

If You See Mold or Rot

If you find a tuber that has turned soft, black, or fuzzy with mold, remove it immediately and throw it away. Check the surrounding tubers for any signs of spread. This is usually caused by too much moisture or poor airflow. If the storage medium feels soggy, replace it with fresh, dry material.

If They Start Sprouting Early

If you see long white sprouts appearing in February or March, your storage area is likely too warm. Move the boxes to a cooler spot. Don't worry about the sprouts themselves; you can carefully trim them back or simply be extra gentle with them when it’s time to plant.

Preparing for Spring Replanting

As the days grow longer and the ground begins to thaw, it's time to start thinking about getting your dahlias back into the garden.

Wait until all danger of frost has passed and the soil has warmed to at least 60°F. How to Plant Dahlias can help if you want a refresher before you get started.

When you bring your tubers out of storage, they might look a little "sleepy," but once they hit that warm spring soil, they will quickly spring to life. If you find that a few didn't make it through the winter, don't be discouraged—it is a normal part of the process, and it gives you a great excuse to try a few new varieties!

Conclusion

Saving dahlia tubers is one of the most rewarding skills a gardener can learn. It turns a one-season display into a lifetime of beauty. By paying attention to the signals of the first frost, digging with a gentle hand, and providing a cool, stable winter home, you can enjoy your favorite blooms year after year.

At Longfield Gardens, our goal is to help you grow a garden you love. We stand behind the quality of our plants and want to see your landscape thrive. Remember that gardening is a journey of learning, and every season brings new opportunities to see what works best in your unique soil and climate.

What to do next:

• Check your USDA zone to see if digging is required.
• Gather your garden fork, labels, and storage boxes, then browse our dahlia collections when you start planning next year's display.
• Wait for that first frost to signal the start of the harvest, then browse our new dahlias for fresh ideas.
• Browse our dinnerplate dahlias for more tips on creating a stunning dahlia display.

We are here to support you with premium quality of our plants and practical advice every step of the way. If you ever have questions about your plants' performance, our team is ready to help. Happy gardening!

FAQ

Do I have to wait for a frost to dig up my dahlias?

While it is best to wait for a killing frost because it signals the tubers to go dormant and toughen their skin, you can dig them up earlier if your schedule requires it. If you must dig before a frost, try to wait until at least late October or early November so the tubers have had maximum time to grow and store energy.

Can I store dahlia tubers in the refrigerator?

While a refrigerator provides the right temperature (40-50°F), it is generally too dry for long-term tuber storage, and the lack of airflow can sometimes lead to rot. If you have a dedicated "beverage" or spare fridge, it can work, but you must monitor moisture levels very closely. Avoid storing them in the same fridge as ripening fruits, which release gases that can damage the tubers.

What happens if I accidentally slice a tuber while digging?

Don't worry! It happens to the best of us. If you slice a tuber but the neck and the connection to the crown are still intact, the tuber will usually heal itself. You can trim off the ragged edge with a clean knife and let it dry. As long as the "eye" on the crown is healthy, the plant can still grow next year.

Is it okay to leave dahlias in the ground in Zone 7?

Zone 7 is the "borderline" zone. In a mild winter with heavy mulching (6-12 inches of straw or leaves), dahlias may survive. However, in a particularly cold or wet winter, they are very likely to rot or freeze. If you have a variety you absolutely love and don't want to lose, digging them up is the only way to ensure their survival.