Introduction
The sight of a dahlia in full bloom is one of the most rewarding experiences a gardener can have. These plants are famous for their incredible diversity, offering everything from tiny pompons to massive dinnerplate varieties in nearly every color imaginable. Because they are so stunning, it is only natural to want that beauty to return to your garden every summer.
At Longfield Gardens, we want to help you enjoy these spectacular flowers year after year. While dahlias are often treated as annuals in many parts of the United States, they are actually perennials. This means the plants have the potential to grow, bloom, and return for many seasons if they receive the right care during the winter months.
This guide is designed for home gardeners who want to know exactly how to ensure their dahlias grow again next year. Whether you live in a warm southern state or a chilly northern region, we will walk you through the simple steps to protect your plants. With a little bit of planning, your favorite dahlia varieties can become a permanent part of your summer landscape.
Understanding the Dahlia Lifecycle
To understand how dahlias return, it helps to look at what is happening beneath the soil. Unlike many common garden perennials that have fibrous root systems, dahlias grow from tubers. These tubers look a bit like a bunch of sweet potatoes joined together at a central point, known as the crown.
Throughout the spring and summer, the tuber provides the energy needed to send up stems and produce flowers. As the season progresses, the plant actually works to grow new tubers and expand the existing ones. These tubers serve as a storage locker for nutrients and energy. This stored energy is exactly what the plant uses to sprout again when the weather warms up the following spring.
In their native habitat of Mexico and Central America, dahlias grow in a cycle of summer rain and winter dormancy. In these regions, the ground never freezes. For a dahlia to grow again next year in your garden, the tubers must be kept in conditions that mimic this natural cycle. They need a period of rest in cool, but not freezing, temperatures.
Determining Your Gardening Zone
Whether your dahlias will grow again on their own depends largely on your local climate. Gardeners use the USDA Plant Hardiness Zone Map to understand which plants can survive the winter in their specific area. Dahlias are considered "tender perennials," which means they are sensitive to freezing temperatures.
Success in Warm Climates (Zones 8 to 11)
If you live in USDA zones 8, 9, 10, or 11, you are in luck. In these warmer regions, winter temperatures rarely drop low enough to freeze the ground deeply. This means your dahlia tubers can usually stay right in the garden all year round. The soil acts as a natural insulator, keeping the tubers tucked away until spring.
Challenges in Cold Climates (Zones 3 to 7)
For gardeners in zones 3 through 6, and often zone 7, the ground will freeze hard enough to damage or kill the dahlia tubers. In these areas, the plants will behave like annuals and die off completely if left unprotected. To see them grow again next year, you must intervene by lifting the tubers from the ground and storing them indoors where they are safe from the frost.
Key Takeaway: Dahlias are perennial plants that store energy in tubers. Their ability to return next year depends on protecting those tubers from freezing winter temperatures.
Leaving Dahlias in the Ground
If you live in a warm climate where the ground does not freeze, letting your dahlias grow back naturally is a simple process. However, even in warm zones, a little bit of winter preparation helps ensure the best results for the following season.
Winterizing Your Garden Beds
Once the first frost hits or the plant begins to yellow and die back in late autumn, it is time to tidy up. Cut the stems down to about 3 or 4 inches above the soil level. This removes the old foliage which can sometimes harbor pests or diseases.
In Zone 7 and even Zone 8, adding a thick layer of mulch is a great way to provide extra insurance. Use about 4 to 6 inches of organic material like shredded bark, straw, or pine needles. This mulch layer acts like a warm blanket, regulating the soil temperature and preventing moisture from evaporating too quickly.
The Importance of Drainage
One of the biggest reasons dahlias might fail to return in warm climates isn't actually the cold—it is the water. "Drainage" refers to how quickly water moves through your soil. Dahlias prefer to stay relatively dry during their dormant winter months.
If your garden bed sits in a low spot where water collects, the tubers are likely to rot. If you have heavy clay soil that holds onto moisture, consider planting your dahlias in raised beds. This keeps the tubers above the water line and ensures they stay healthy and firm until spring.
How to Dig and Lift Dahlia Tubers
For gardeners in colder regions, lifting the tubers is the most reliable way to make sure dahlias grow again next year. This process might seem technical, but it is actually a straightforward garden task that can be done in an afternoon.
Timing the Harvest
The best time to dig up your dahlias is right after the first "killing frost." You will know this has happened when the lush green leaves of your dahlias suddenly turn black or dark brown overnight. This frost signals to the plant that it is time to go dormant.
Wait about a week after this first frost before you start digging. This short waiting period allows the tubers to "cure" slightly in the ground, which helps toughen their skins for storage. However, do not wait so long that the ground begins to freeze hard, as this can damage the tubers.
Step-by-Step Digging Process
- Cut the Stems: Use sharp garden shears to cut the stems down to about 4 inches above the ground.
- Loosen the Soil: Use a digging fork or a shovel to gently loosen the soil in a circle around the plant. Start at least 12 inches away from the main stem to avoid accidentally slicing into the tubers.
- Lift Carefully: Gently pry the entire root ball upward. It is often helpful to have a second person help lift the clump if the plant grew very large over the summer.
- Remove Excess Soil: Shake the clump gently or use your hands to brush away the largest chunks of soil. Do not wash them with a hose unless your soil is very heavy clay, as adding extra moisture right before storage can encourage rot.
Action Steps for a Successful Harvest
- Label each plant with its variety name using waterproof tape or tags before the frost hits.
- Use a garden fork instead of a shovel if possible, as the tines are less likely to cut the tubers.
- Work slowly to avoid snapping the "neck" of the tuber, which is the narrow part where it connects to the stem.
Drying and Curing for Storage
Before you put your tubers away for the winter, they need a short period of drying. This is often called "curing." Curing allows any small nicks or cuts from the digging process to heal over, creating a protective callus.
Place your lifted tubers in a cool, dry area that is protected from direct sunlight and frost. A garage, shed, or covered porch works well. Lay them out in a single layer on top of newspaper or cardboard. Let them sit for about 2 to 3 days.
During this time, the skin will dry out slightly. You want the tubers to feel firm, like a fresh potato. If they start to look shriveled or wrinkled, they have been drying for too long. Once they are dry to the touch, they are ready for their winter home.
Choosing the Right Storage Container
The goal of winter storage is to keep the tubers in a "Goldilocks" state: not too wet, or they will rot, and not too dry, or they will shrivel up and die. The container you choose plays a big role in maintaining this balance.
Cardboard Boxes and Paper Bags
These are excellent choices because they are "breathable." They allow a small amount of air circulation, which prevents moisture from building up around the tubers. You can layer the tubers in a box, separating each layer with newspaper.
Plastic Bins and Crates
If you use plastic storage bins, do not snap the lid on tight. Leave the lid cracked or drill several small holes in the sides of the bin to allow for air exchange. Many gardeners find success using open plastic milk crates lined with newspaper.
Storage Mediums
To keep the tubers from drying out completely, most gardeners pack them in a "medium." Common choices include:
- Peat Moss: Holds a tiny bit of moisture but stays fluffy.
- Vermiculite: A mineral that provides great insulation and moisture control.
- Wood Shavings: Often sold as pet bedding, these are inexpensive and effective.
- Dry Potting Soil: Simple and easy to find.
Key Takeaway: Proper storage requires a balance of humidity and airflow. Use breathable containers and a packing medium to keep tubers firm and healthy through the winter.
Finding the Perfect Storage Location
Where you put your containers is just as important as how you pack them. The ideal storage temperature for dahlia tubers is between 40°F and 50°F.
Ideal Spots
An unheated basement, a root cellar, or a crawl space are usually the best locations. These areas stay cool enough to keep the plant dormant but are insulated enough to prevent freezing. If you have an attached garage, it may stay within this temperature range, but be careful of spots near the garage door where cold drafts can sneak in.
Areas to Avoid
Avoid storage near a furnace, water heater, or any heat vents. These spots will be too warm and will cause the tubers to wake up early or dry out. Likewise, do not store them in a location that drops below freezing. A single night of freezing temperatures in your storage area can turn your tubers into mush, meaning they will not grow again next year.
Checking on Your Tubers During Winter
Think of your stored dahlias as sleeping guests. You don't want to disturb them too much, but it is a good idea to check on them about once a month.
When you check them, look for any signs of trouble. If a tuber feels soft, mushy, or has a foul smell, it is beginning to rot. Remove it immediately and throw it away so the rot doesn't spread to the healthy tubers nearby.
If the tubers look very wrinkled and feel light, they are getting too dry. You can lightly mist the packing medium with a spray bottle of water. You don't want the medium to be "wet," just slightly damp to the touch. This small adjustment is often all it takes to keep them in perfect condition until spring.
Dividing Your Dahlias
One of the most exciting parts of learning how to make dahlias grow again next year is that you will eventually end up with more plants than you started with. As a dahlia grows, the tuber clump expands. After a year or two, you can divide these clumps into several smaller pieces, each of which will grow into a brand-new plant.
When to Divide
You can divide your tubers in the fall right after digging, or in the spring before planting. Many beginners find it easier to wait until spring. During the winter, the "eyes" of the dahlia (the small bumps where new growth starts) become more prominent and easier to see.
Finding the Eye
An "eye" looks like a tiny pimple or a small green sprout located on the crown of the tuber. For a division to grow, it must have at least one eye. If you cut off a beautiful, fat tuber but it doesn't have an eye attached to it, that tuber will never sprout.
How to Make the Cut
Use a clean, sharp pair of garden snips or a small knife. Carefully cut a single tuber away from the main clump, making sure to include a piece of the crown where the eye is located. If the clump is very large, you can simply cut it into halves or quarters, ensuring each section has several healthy tubers and at least one visible eye.
Waking Up Your Dahlias in Spring
As the days get longer and the weather warms up, it is time to get your dahlias ready for the garden. About 4 to 6 weeks before the last expected frost date in your area, you can begin the "waking up" process.
Move your storage containers to a warmer spot, around 60°F to 65°F. This tells the tubers that spring is arriving. You will soon see the eyes begin to sprout and turn into small green shoots.
Potting Up Early
If you live in a region with a short growing season, you can give your dahlias a head start by planting them in pots indoors. Use a standard potting mix and a container with drainage holes. Place them in a sunny window or under grow lights. By the time the weather is warm enough to plant outside, you will already have a small plant ready to go. This often leads to earlier blooms in the summer.
Replanting in the Garden
The final step in ensuring your dahlias grow again next year is getting them back into the ground at the right time. Timing is the most important factor here.
Wait for Warm Soil
Dahlias love warm weather. Planting them in cold, wet spring soil can cause the tubers to rot before they have a chance to grow. Wait until the danger of frost has completely passed and the soil has warmed up to at least 60°F. A good rule of thumb is to plant your dahlias around the same time you would plant tomatoes or peppers.
Choosing the Spot
Select a location that gets at least 6 to 8 hours of direct sunlight. Sunlight is the "fuel" that dahlias use to produce those big, beautiful flowers. Ensure the soil is well-drained and enriched with a bit of compost.
Planting Depth and Spacing
Dig a hole about 4 to 6 inches deep. Lay the tuber horizontally in the hole with the sprout or "eye" facing upward. If you are planting several dahlias, space them about 18 to 24 inches apart. This gives them plenty of room to grow and ensures good air circulation around the leaves, which helps prevent mildew.
At Longfield Gardens, we recommend waiting to water your dahlias until you see the first green shoots poking through the soil. The tubers have plenty of stored moisture to get started, and overwatering early on is a common cause of rot. Once the plant is about 6 inches tall, you can begin a regular watering and fertilizing schedule.
Troubleshooting Spring Growth
If your dahlias don't seem to be sprouting as quickly as you expected, don't worry. Sometimes tubers take a little longer to wake up depending on the variety and the soil temperature.
Check the Soil Temperature
If the spring has been particularly cold and rainy, the tubers might just be waiting for more heat. You can check your soil temperature with a simple kitchen thermometer. If it is below 60°F, the plant is simply being patient.
Inspect for Firmness
If several weeks have passed and you see no growth, you can gently brush away a little bit of soil to check the tuber. If it feels firm, it is still healthy and will sprout eventually. If it feels soft or hollow, it may have rotted, and you should replace it with a fresh dahlia tuber.
Watch for Pests
Sometimes, slugs or snails will nibble on the very first shoots that emerge from the ground. If you see "disappearing" sprouts, look for silvery trails on the soil. Using a pet-friendly slug bait or a simple physical barrier can protect those tender new leaves as they grow.
Summary of the Yearly Cycle
Managing your dahlias so they grow again next year is all about following the natural rhythm of the seasons.
- Spring: Plant tubers in warm soil once the frost is gone.
- Summer: Enjoy the blooms, keep them watered, and remove spent flowers (deadheading) to encourage more growth.
- Fall: After the first frost, either mulch them heavily (warm zones) or dig them up (cold zones).
- Winter: Store tubers in a cool, dark, frost-free place and check on them monthly.
By following these simple steps, you transform a one-season flower into a long-term investment. Many gardeners find that their dahlia collection grows and improves every year, providing an even more spectacular display as the tubers mature and the clumps are divided.
Conclusion
Growing dahlias is a rewarding hobby that brings incredible color and joy to the garden. While the idea of "overwintering" might seem like a lot of work at first, it quickly becomes a satisfying part of the gardening year. Protecting your tubers ensures that your favorite colors and shapes will be back to greet you every summer.
At Longfield Gardens, we are committed to helping you succeed with every bulb and tuber you plant. Our 100% quality guarantee means we stand behind the health and variety of our plants, so you can start your dahlia journey with confidence. Whether you are trying to save your very first tuber or expanding a large collection, we are here to support you with practical advice and high-quality dahlia collections.
What to do next:
- Identify your USDA gardening zone to decide if you need to dig or mulch.
- Prepare your storage supplies (boxes, peat moss, labels) before the first frost.
- Enjoy your late-summer blooms and start planning where your divided tubers will go next spring!
Gardening is about patience and the excitement of seeing life return to the soil each year. With these simple techniques, you can look forward to a garden full of dahlias for many seasons to come.
FAQ
Do I have to dig up my dahlias every year?
This depends on where you live. If you are in USDA zones 8 through 11, you can usually leave your dahlias in the ground with a layer of mulch. If you live in zone 7 or colder, the ground will freeze deep enough to kill the tubers, so you must dig them up and store them indoors to keep them alive.
Will my dahlias come back if I just leave them alone?
In warm climates, yes, they will sprout again on their own in the spring. In cold climates, however, the tubers will rot or freeze over the winter, and the plant will not return. In those areas, dahlias act like annuals unless you provide winter protection by lifting and storing the tubers.
What is the best material to store dahlia tubers in?
The most successful storage mediums are peat moss, vermiculite, or wood shavings (pet bedding). These materials help maintain a steady moisture level around the tuber, preventing them from drying out too much while still allowing the tubers to breathe so they don't rot. For additional guidance, see this dahlia tuber storage guide.
When is the best time to replant my stored dahlia tubers?
Wait until the soil has warmed up to at least 60°F and there is no longer any danger of frost. This is usually in late spring, around the same time you would plant tomatoes. Planting too early in cold, wet soil is the most common cause of tubers rotting in the spring. For seasonal ordering details, review Longfield Gardens' shipping information.
