Introduction
There is nothing quite like the sight of a dahlia garden in full bloom during the late summer months. From the massive, pillowy petals of dinnerplate varieties to the intricate, geometric shapes of pompon types, these plants are the undisputed stars of the autumn landscape. After a season of enjoying such spectacular color, it is natural to want to protect that investment so you can enjoy the same beautiful flowers next year.
Whether or not you dig up dahlia bulbs—which are technically called tubers—every year is one of the most common questions we hear at Longfield Gardens. The answer depends largely on where you live and how much effort you want to put into expanding your collection. While dahlias are tender perennials, they are surprisingly resilient if you follow a few basic principles of winter care.
In this guide, we will help you determine if your local climate requires you to lift your tubers or if you can safely leave them in the ground. We will also walk you through the simple steps for digging, curing, and storing them so they stay healthy and ready for spring planting. Our goal is to make dahlia care feel like a rewarding part of your gardening rhythm rather than a difficult chore.
The Short Answer: Do You Need to Dig?
The decision to dig up your dahlias usually comes down to your USDA hardiness zone. Dahlias are native to the warm mountain regions of Mexico and Central America, which means they are not naturally equipped to survive freezing soil. They are considered "tender" because their thin-skinned tubers contain a lot of water, making them prone to freezing and rotting in cold, wet conditions. For zone guidance, start with our Hardiness Zone Map.
As a general rule, if you live in USDA zones 8, 9, or 10, your dahlias can typically stay in the ground all year. In these warmer climates, the soil rarely freezes deep enough to reach the tubers. However, if you live in zone 7 or colder, the ground will likely freeze deep enough to kill the plant, making it necessary to dig them up and store them indoors.
Even if you live in a warm area, you might still choose to dig them up every two or three years. Dahlia clumps grow larger each season, and eventually, they can become overcrowded. Digging them up allows you to divide the clumps, which keeps the plants healthy and gives you "extra" tubers to plant in other parts of your yard or share with friends.
Key Takeaway: Check your USDA hardiness zone first. If you are in zone 7 or colder, plan to dig your dahlias. In zone 8 or warmer, you can usually leave them in the ground with a little extra protection.
When to Dig: Timing is Everything
Timing is one of the most important factors in successfully overwintering your dahlias. It can be tempting to clear out the garden as soon as the weather turns chilly, but waiting for the right moment helps the tubers store the energy they need for next year’s growth.
The First Frost Rule
We recommend waiting until the first "killing frost" before you start digging. You will know this has happened when the lush green foliage of your dahlias turns black or dark brown overnight. While the top of the plant looks finished, this cold snap actually signals the tubers to go into dormancy. If you want a visual refresher on the plant forms you may be saving, our Dahlia Flower Forms guide is a helpful reference.
If possible, let the blackened plants sit in the ground for about a week to ten days after the frost. During this short window, the "eyes" (the small bumps where next year’s stems will grow) become more visible, and the skin of the tubers begins to toughen up. This makes them more durable for storage.
Watching the Weather
While waiting is beneficial, you must get the tubers out of the ground before the soil itself freezes solid. A light frost only affects the leaves and stems, but a deep freeze will turn the tubers into mush. If your local forecast predicts a week of temperatures well below freezing, it is time to get your garden fork and start digging.
What to do next:
- Keep a close eye on your local weather forecast starting in late September.
- Locate your garden fork and storage containers ahead of time.
- Label your dahlias while they are still in bloom so you know which variety is which after the foliage dies back.
How to Dig Up Dahlia Tubers Step-by-Step
Digging up dahlias is a straightforward process that requires only a few basic tools. The goal is to lift the entire clump without puncturing or snapping the individual tubers.
Step 1: Cut Back the Stems
Once the foliage has died back, use a pair of clean garden pruners to cut the main stems. We suggest leaving about 4 to 6 inches of the stem attached to the clump. This remaining stem serves as a convenient handle when you are lifting the tubers and helps you keep track of where the center of the clump is located.
Step 2: Loosen the Soil
Use a garden fork rather than a shovel if you have one. A fork is less likely to slice through the tubers. Start digging about 12 inches away from the center stem. Gently push the fork into the soil and rock it back and forth to loosen the earth. Work your way all the way around the plant in a wide circle.
Step 3: Lift the Clump
Once the soil is loose, slide the fork under the clump and gently pry it upward. Avoid pulling hard on the stem handle, as the "necks" of the tubers (the thin part connecting the tuber to the stem) are very fragile. If the neck breaks, that specific tuber may not be able to grow next year.
Step 4: Remove Excess Dirt
Gently shake the clump to remove large chunks of soil. You can use your hands to brush away loose dirt, but be careful not to skin the tubers. At this stage, many gardeners prefer to leave some soil on the tubers to protect them, while others prefer to wash them clean. In our experience, either method can work, provided the tubers are allowed to dry properly before storage.
The Importance of Curing
Curing is the process of letting the tubers dry out slightly so they can develop a "skin" that protects them from rot and dehydration. This is a vital step that shouldn't be skipped.
After you have lifted the tubers and removed the bulk of the dirt, move them to a protected area that is out of direct sunlight but has good air circulation. A garage, a shed, or a covered porch works well. Turn the clumps upside down so any water trapped in the hollow stems can drain out.
Let the tubers sit for 1 to 3 days. They should feel dry to the touch, and any remaining soil should be easy to brush off. Do not leave them out for too long, or they will begin to shrivel. The goal is "dry on the outside, plump on the inside."
Key Takeaway: Curing prepares the tuber for its winter nap. A few days in a dry, shaded spot helps prevent rot during the long months of storage.
Storing Dahlias for a Successful Spring
The biggest challenge with storing dahlias is finding the "Goldilocks" environment: not too cold, not too warm, not too wet, and not too dry. If you need a refresher on the digging and packing process, our How to Overwinter Dahlias article walks through the same basics in more detail.
The Ideal Storage Conditions
Dahlias prefer to be stored in a dark, cool place where the temperature stays between 40°F and 50°F. If the area is too warm, the tubers will think it is spring and start to sprout or shrivel up from dehydration. If it gets below freezing, the tubers will die. Unheated basements, crawl spaces, or insulated garages are often the best spots.
Choosing a Storage Medium
To prevent the tubers from drying out completely, we recommend packing them in a medium that holds a tiny bit of moisture. Popular options include:
- Peat moss: This is a classic choice that provides great insulation.
- Vermiculite: This holds moisture well and is very clean to work with.
- Wood shavings: Pine shavings (like the kind used for pet bedding) are excellent for airflow.
- Dry sand: A traditional method that works well in very dry climates.
Packing the Tubers
Place a layer of your chosen medium in the bottom of a cardboard box or a plastic bin. If using plastic, do not seal the lid tightly; the tubers need to "breathe" to prevent mold. Arrange the tubers in a single layer so they aren't touching, then cover them with more packing material. You can stack a second layer on top if needed.
Leaving Dahlias in the Ground: Tips for Warm Climates
If you are lucky enough to live in a region where the ground doesn't freeze (Zones 8-10), you can save yourself some work by leaving your dahlias in place. However, they still need a bit of winter preparation to ensure they return vigorously in the spring.
Mulching for Protection
Even in warm climates, a sudden cold snap can happen. After you cut the stems back in late autumn, cover the dahlia bed with a thick layer of mulch. Use 4 to 6 inches of straw, shredded leaves, or wood chips. This acts like a blanket, keeping the soil temperature stable.
The Danger of Winter Wetness
In many areas, winter is the rainiest season. While dahlias love water during the summer, they hate sitting in cold, soggy soil during their dormant period. If your garden has heavy clay soil or a spot that collects water, you may need to dig your tubers even if you live in a warm zone. If the tubers sit in a puddle all winter, they will almost certainly rot.
Winterizing containers
If you grow your dahlias in pots, we recommend moving the entire container into a garage or shed for the winter. Pots are much more exposed to the elements than the ground, and the soil inside can freeze much faster. Simply cut the stems back, stop watering, and move the pot to a cool, dark corner until spring.
Why Digging Every Few Years is a Good Idea
Even if you live in a climate where dahlias are hardy, there are several benefits to digging them up every two or three years. If you want to shop more varieties before deciding what to save, start with New Dahlia Collections.
Dividing for Health
A single dahlia tuber planted in the spring will grow into a massive clump by the end of the season. Over several years, these clumps can become so large that the tubers in the center struggle to get enough nutrients. This can lead to smaller flowers and weaker stems. By digging and dividing the clump into individual tubers, you rejuvenate the plant.
Expanding Your Garden
One of the best things about dahlias is that they are "the gift that keeps on giving." A healthy clump can often be divided into 3 to 5 new tubers, each capable of growing into a full-sized plant the following year. This is the most cost-effective way to fill your garden with your favorite varieties, like the classic yellow 'Kelvin Floodlight' or the stunning Dahlia Dinnerplate Cafe Au Lait.
Preventing Pests and Disease
Lifting the tubers gives you a chance to inspect them. You can easily spot any signs of rot or pest damage that might be hidden underground. It also allows you to refresh the soil with compost before replanting in the spring, ensuring your dahlias have the best possible start.
Understanding Tuber Anatomy: Necks, Crowns, and Eyes
When you are digging or dividing your dahlias, it helps to know a little bit about their anatomy. This ensures you don't accidentally throw away a perfectly good tuber or save one that won't grow.
- The Tuber: This is the fat, potato-like part that stores energy.
- The Neck: This is the narrow part that connects the tuber to the main stem. It is very easy to break, so handle it with care.
- The Crown: This is the area where the neck meets the old stem.
- The Eye: This is the most important part. The eye is a tiny, often pinkish bud located on the crown. It is the only part of the tuber that can grow a new sprout.
A tuber without an eye is "blind" and will never grow a plant, even if the tuber itself looks healthy. This is why we recommend waiting until after the first frost to dig—the cold helps those eyes swell and become easier to see.
Common Mistakes to Avoid
Gardening is a learning process, and we want to help you skip the most common pitfalls when it comes to dahlia winter care. If you plan to store tubers for shipment or compare season timing, the Shipping Information page is also useful.
Digging Too Early
If you dig your dahlias while the weather is still warm and the plants are actively growing, the tubers may be "green" and soft. These don't store nearly as well as tubers that have been allowed to cure in the ground after a frost. Patience is rewarded with much higher survival rates in storage.
Using Air-Tight Containers
It is tempting to put tubers in a sealed plastic bag to keep them neat, but this is a recipe for rot. Tubers are living things that release a small amount of moisture and gases even while dormant. Without airflow, that moisture gets trapped and encourages fungus. Always use breathable containers like cardboard boxes, paper bags, or plastic bins with the lids left slightly ajar.
Forgetting the Labels
It might seem like you will remember which clump is which, but by April, every tuber looks identical. Use a waterproof marker to write the variety name directly on the skin of the tuber or tie a tag to the stem. We at Longfield Gardens always suggest labeling as you dig to prevent any mix-ups.
When to Check on Your Stored Tubers
Your job isn't quite finished once the dahlias are in the basement. We recommend checking on your stored tubers once a month during the winter.
If you notice a tuber is starting to rot (it will feel mushy or smell bad), remove it immediately so the rot doesn't spread to the healthy ones. If the tubers look very shriveled and wrinkled like a raisin, they are too dry. You can give the packing medium a very light misting with water to restore a bit of humidity, but be careful not to make it wet.
A tiny bit of shrivelling is normal and usually nothing to worry about. As long as the tuber feels firm when you squeeze it, it is healthy and ready for spring.
Replanting in the Spring
When the days start to lengthen and the threat of frost has passed, it is time to bring your dahlias out of hibernation.
In most areas, you can plant your tubers directly in the garden once the soil temperature reaches about 60°F. If you want a head start on the blooming season, you can "start" your tubers indoors in pots about 4 to 6 weeks before the last frost date. This gives them a chance to develop roots and a few inches of growth so they are ready to take off as soon as they hit the warm garden soil.
Remember the simple rule of "Right Plant, Right Place." Dahlias need full sun—at least 6 to 8 hours a day—and soil that drains well. When you plant, place the tuber horizontally about 4 to 6 inches deep, with the eye pointing upward.
Conclusion
Digging up dahlia bulbs every year might seem like an extra step, but for many gardeners, it is a cherished part of the season. It marks the transition from the exuberant colors of summer to the quiet rest of winter. Whether you are lifting them to save them from a northern freeze or dividing them to share with neighbors in the south, the effort you put in now ensures a spectacular show next year.
At Longfield Gardens, we want you to feel confident in every step of your gardening journey. By matching your winter care to your local climate and following these simple steps for digging and storage, you can enjoy your favorite dahlia varieties for many years to come.
- Wait for the first frost to signal dormancy.
- Dig carefully with a garden fork to protect the tuber necks.
- Cure and store in a cool, dry place between 40°F and 50°F.
- Check monthly to ensure your tubers stay firm and healthy.
Growing dahlias is a journey that rewards patience and care with some of the most breathtaking blooms in the world. With a little winter preparation, you can look forward to another season of incredible color in your own backyard.
FAQ
Can I leave dahlias in the ground in Zone 7?
In Zone 7, leaving dahlias in the ground is a bit of a gamble. If you have very well-draining soil and provide a thick layer of mulch (6-8 inches), they may survive a mild winter. However, if the winter is particularly wet or cold, the tubers are likely to rot. Most gardeners in Zone 7 choose to dig them up just to be safe.
Do I have to wash the dirt off the tubers before storing?
You do not strictly have to wash them. Some gardeners find that leaving a bit of native soil on the tubers helps protect them from drying out. However, washing them makes it much easier to see the "eyes" and identify any signs of rot. If you do wash them, just ensure they are 100% dry on the surface before you pack them away.
What happens if I don't dig up my dahlias in a cold climate?
If the ground freezes several inches deep, the water inside the dahlia tuber will freeze, expand, and break the cell walls. Once the ground thaws, the tuber will turn into a soft, rotten mass. It will not grow back in the spring. In cold climates, digging is the only way to ensure the plant survives.
How do I know if a stored tuber is still alive in the spring?
A healthy tuber should feel firm, similar to a fresh potato. If it is slightly wrinkled but still firm, it is usually fine. Look for the "eye" near the stem end; if you see a tiny green or pink sprout beginning to form, the tuber is definitely alive and ready to be planted. If the tuber is mushy, hollow, or completely dried out like a piece of wood, it is likely dead.
