Introduction
There is a special kind of magic in the late summer garden when dahlias begin to bloom. These plants are famous for their incredible variety, offering everything from tiny pompons to massive dinnerplate blooms that can reach the size of a volleyball. For many home gardeners, the first season of growing dahlias is the start of a lifelong passion. The colors are so vivid and the flowers are so abundant that it is natural to want that same beauty to return next summer.
The short answer is that dahlias are perennials, meaning they are capable of growing back every year. However, because they are native to the warm mountain regions of Mexico and Central America, they are not naturally equipped to survive freezing winter temperatures. Whether they return on their own or require a little extra help from you depends largely on where you live.
At Longfield Gardens, we want to help you enjoy these spectacular flowers season after season. This guide will explain how the dahlia life cycle works and what steps you can take to ensure your favorite varieties come back even stronger next year. Whether you live in a warm climate or a region with snowy winters, you can successfully grow dahlias as a permanent part of your landscape.
Understanding the Dahlia Life Cycle
To understand if dahlias will grow every year in your garden, it helps to look at how the plant stores its energy. Dahlias grow from underground structures called tubers. These tubers look a bit like a bunch of narrow potatoes or carrots clustered together at the base of the stem.
The tuber acts like a storage battery for the plant. During the spring and summer, the leaves of the dahlia soak up sunlight and turn it into energy. Some of that energy goes toward producing those famous flowers, but the rest is sent underground to be stored in the tubers. This stored energy is what allows the plant to sprout again after its winter nap.
In their native environment, dahlias go through a period of dormancy during the cooler, drier months. The top of the plant dies back, but the tubers stay safe and snug underground. When the rains return and the soil warms up, the tubers send up new shoots. In the United States, we can replicate this cycle, though our "winter" often requires us to intervene to protect those energy-packed tubers from the cold.
Key Takeaway Dahlias are botanically classified as "tender perennials." This means they have a perennial life cycle but lack the hardiness to survive deep freezes without protection.
Do Dahlias Come Back on Their Own?
Whether your dahlias sprout again without any effort on your part depends on your local weather and soil conditions. This is where USDA Plant Hardiness Zones come into play. These zones are based on the average minimum winter temperature in your area.
Growing Dahlias in Warm Climates (Zones 8–11)
If you live in USDA zones 8, 9, 10, or 11, you are in luck. In these warmer regions, the ground rarely freezes deep enough to reach the dahlia tubers. For gardeners in these areas, dahlias typically behave like traditional perennials. After the flowers finish blooming in the fall, the foliage will eventually turn yellow or brown. You can cut the stems down to a few inches above the ground and leave the tubers right where they are.
In these zones, the biggest threat to dahlias is not the cold, but rather excessive moisture. If your soil stays very wet and soggy during the winter, the tubers may rot. Well-draining soil—which is soil that allows water to move through it quickly—is the secret to success for in-ground overwintering.
Growing Dahlias in Cold Climates (Zones 3–7)
For gardeners in zones 3 through 7, winter temperatures regularly drop well below freezing. If dahlia tubers are left in the ground in these regions, the water inside the tubers will freeze. This causes the cells to burst, and the tubers will turn into a soft, mushy mess by spring.
In these cooler climates, you have two choices:
- Treat them as annuals: Some gardeners choose to plant new tubers every spring. This is a great way to try out new colors and shapes each year without the work of winter storage.
- Lift and store the tubers: If you have a favorite variety that you want to save, you can "lift" (dig up) the tubers in the fall and keep them in a frost-free place until spring.
When to Move Dahlias Indoors
If you live in a cold climate and want your dahlias to grow every year, timing is the most important factor. You want to give the plant as much time as possible to store energy, but you must get the tubers out of the ground before the soil freezes solid.
The best signal to start this process is the first "blackening" frost. This is a frost heavy enough to turn the dahlia’s green leaves into a dark, wilted brown. While the foliage is ruined, this frost actually sends a signal to the tubers to go into deep dormancy.
Wait about a week after this frost before you start digging. This short waiting period allows the "eyes" (the small bumps where next year’s sprouts will come from) to become more visible. However, do not wait so long that the ground begins to freeze hard, as this can damage the tubers.
What to do next
- Keep a close eye on your local weather forecast in late autumn.
- Gather your supplies: a garden fork, labels, and storage containers.
- Wait for the foliage to turn brown after a frost before you begin digging.
How to Lift and Store Dahlia Tubers
Lifting tubers might sound like a big task, but it is a straightforward process once you get the hang of it. Think of it as putting your garden to bed for the winter. Following these steps will give your dahlias the best chance of returning next year.
Step 1: Digging with Care
Start by cutting the stalks down to about four to six inches above the ground. Use a garden fork rather than a shovel if possible. Shovels are more likely to slice through the tubers. Insert the fork into the soil about a foot away from the stem and gently pry upward. Work your way around the plant until the entire clump of tubers lifts easily out of the earth.
Step 2: Cleaning and Curing
Gently shake off the excess soil. You can use your hands or a soft brush to remove the dirt. Some gardeners like to wash their tubers with a garden hose, but if you do this, you must ensure they dry completely.
"Curing" is the process of letting the tubers dry out slightly so the outer skin can toughen up. Place your tubers in a cool, dry area that is protected from direct sunlight and frost. A garage or a covered porch works well. Let them sit for a few days until the surface feels dry to the touch.
Step 3: Packing for Winter
Once dry, place the tubers in a breathable container. Cardboard boxes, paper bags, or plastic bins with holes for ventilation are all good choices. We recommend nesting the tubers in a packing medium to keep them from drying out too much. Common choices include:
- Coarse vermiculite
- Peat moss
- Wood shavings (the kind used for pet bedding)
The goal is to keep the tubers slightly insulated but not airtight. Store the containers in a dark, cool place where the temperature stays between 40°F and 50°F. A cool basement, an unheated crawl space, or an insulated garage is usually ideal. For a detailed overview, see this guide to storing dahlia tubers in winter.
Step 4: Monthly Checks
About once a month, take a quick peek at your stored tubers. If they look shriveled like a dried raisin, mist them very lightly with water. If you see any soft or moldy spots, cut those sections away and discard them so the rot doesn't spread to the healthy tubers.
Dividing Tubers for More Flowers
One of the most exciting things about dahlias is that they don't just grow back; they multiply. A single tuber planted in the spring will often grow into a large clump of five to ten tubers by the fall. This means you can actually increase your dahlia collection every year for free.
Dividing can be done in the fall before storage or in the spring before planting. Most beginners find it easier to divide in the spring because the "eyes" are much easier to see. The eye is a tiny bump located on the "neck" of the tuber, near where it attached to the main stem. Every division must have at least one healthy tuber, a neck, and a visible eye to grow.
Using a clean, sharp pair of garden shears or a knife, carefully separate the individual tubers from the main clump. This simple step turns one plant into several, allowing you to fill your garden with even more color or share your favorite varieties with neighbors and friends.
Planting for Success the Following Year
When spring arrives and the threat of frost has passed, it is time to bring your dahlias back out into the sunshine. Getting the timing right is the secret to a fast start.
The 60-Degree Rule
Dahlias love warmth. Even if the air feels warm, the soil may still be chilly from winter. For the best results, wait until the soil temperature reaches about 60°F before planting your tubers. If you plant them in cold, wet soil, they may sit idle and are more likely to rot. A simple way to judge is to wait until you are ready to plant your tomatoes or peppers.
Choosing the Right Spot
To ensure your dahlias grow well every year, pick a spot that meets their three basic needs:
- Sunlight: They need at least six to eight hours of direct sunlight per day. More sun usually means more flowers.
- Drainage: Ensure the spot doesn't collect standing water after a rain.
- Space: Give them room to breathe. Depending on the variety, they should be spaced 12 to 24 inches apart.
Planting Depth and Care
Dig a hole about four to six inches deep. Lay the tuber horizontally (flat) in the hole with the eye pointing up. Cover it with soil, but wait to water until you see the first green shoots peeking through the ground. The tuber has enough moisture stored inside to get started, and extra water at this early stage can cause problems. For more detail, read about dahlia planting depth.
Once the plant is about a foot tall, you can begin a regular watering and fertilizing schedule. Deep watering once or twice a week is better than a light sprinkle every day. This encourages the roots to grow deep into the soil, making the plant more resilient.
Key Takeaway Success with dahlias comes down to timing and drainage. Wait for warm soil in the spring and provide a dry "nap" in the winter.
Common Reasons Dahlias Might Not Return
If your dahlias didn't come back this year, don't be discouraged. Gardening is a learning process, and even experienced growers occasionally lose a plant. Here are the most likely reasons a dahlia might not return, along with simple ways to get better results next time.
The Ground Got Too Cold
If you live in a cold zone and left your tubers in the ground, they likely froze. If you prefer not to dig them up, you can try adding a very thick layer (6–12 inches) of clean straw or wood chips over the planting area in the late fall. This acts like a blanket for the soil. However, in zones 6 and colder, lifting the tubers is the only way to be certain they survive.
The Tubers Rotted
This is the most common issue in both summer and winter. In the garden, rot usually happens because the soil is too heavy or the area is a low spot where water gathers. Adding compost to your soil can help improve drainage. In storage, rot happens if the tubers were put away while they were still wet or if they were stored in a plastic bag without any air.
Pests or Wildlife
Occasionally, hungry garden visitors like voles or gophers might find dahlia tubers to be a tasty winter snack. If you have a high population of burrowing animals, growing your dahlias in raised beds or large containers can help protect them.
Using Dahlias as Annuals
While many people enjoy the process of saving tubers, it is perfectly okay to treat dahlias as annuals. At Longfield Gardens, we see many customers who prefer this "fresh start" approach every spring.
Treating dahlias as annuals removes the need for digging, cleaning, and storing tubers during the busy fall season. It also gives you the freedom to redesign your garden every year. One year you might want a "sunset" garden with oranges and reds like 'Cornel' or 'HS Flame'. The next year, you might prefer a soft, romantic look with the creamy tones of 'Café au Lait' and 'Wizard of Pink'.
If you choose this route, you can simply leave the plants in the ground over winter. Once the spring soil warms up, remove the old, decomposed material and plant fresh, high-quality tubers. This approach ensures you start every season with vigorous, healthy plants that are true to their variety.
Growing Dahlias in Containers
If you have limited space or want to keep your dahlias closer at hand, they grow beautifully in pots. This can also make the "grow every year" process a little easier.
For large dahlias, use a container that holds at least five gallons of soil. For smaller "border" or "gallery" varieties, a smaller pot is fine. The most important thing is to ensure the pot has large drainage holes.
When winter comes, you don't necessarily have to dig the tubers out of the pot. If you have a frost-free area like a basement or a garage, you can simply move the entire container indoors. Cut the stems back, stop watering, and let the soil dry out. The soil acts as the storage medium. In the spring, you can tip the pot over, refresh the soil, and start the cycle again.
Why Quality Tubers Matter
Whether you are saving your own tubers or buying new ones each year, starting with quality is the best way to ensure success. A healthy tuber should feel firm, not shriveled or mushy. It should have a clear "neck" and a visible "eye" or sprout.
We work with experienced growers to ensure that the tubers we ship to you are healthy and ready to perform. Because we maintain our own trial garden, we only offer varieties that we know will provide beautiful results for home gardeners. When you start with a strong tuber, the plant has a much better chance of growing vigorously and producing a spectacular show of flowers.
What to do next
- Choose a mix of flower shapes, such as ball dahlias for longevity and "cactus" types for unique texture.
- Plan your garden layout with taller varieties in the back and shorter ones in the front.
- Order your favorites early in the year to ensure the best selection.
Conclusion
Dahlias are one of the most rewarding plants you can grow. Their ability to return year after year makes them a wonderful investment for your landscape. While they may require a little extra attention in colder climates, the reward is a garden filled with spectacular, high-impact color from mid-summer until the first frost.
At Longfield Gardens, we believe that gardening should be a source of joy and relaxation. By following a few simple steps—watching the weather, ensuring good drainage, and providing a safe winter home for your tubers—you can enjoy the beauty of dahlias every single year. Whether you are a beginner or a seasoned pro, there is always something new and exciting to discover in the world of dahlias.
- Dahlias are perennials but need protection from freezing temperatures.
- Zones 8–11 can usually leave tubers in the ground with good drainage.
- Zones 3–7 should lift and store tubers indoors for the winter.
- Timing is key: Wait for warm soil in spring and the first frost in fall.
Gardening is a journey of discovery. Every tuber you plant is a promise of beauty to come, and every year you bring them back is a testament to the wonderful cycle of nature. We are here to support you every step of the way as you create your most beautiful garden yet.
FAQ
Can I leave my dahlias in the ground if I live in Zone 7?
It depends on your specific microclimate and soil. While Zone 7 is on the edge of where dahlias can survive, they often struggle if the winter is particularly wet or if there is a prolonged deep freeze. To be safe, most gardeners in Zone 7 choose to lift their tubers or provide a very heavy layer of protective mulch over the planting area.
Do dahlias grow back bigger every year?
Yes, dahlia clumps naturally grow larger each season. As the underground tuber system expands, the plant often produces more stems and a higher volume of flowers. However, if the clump becomes too crowded after several years, the flowers may get smaller, which is a signal that it is time to divide the tubers.
How long can dahlia tubers live in storage?
Dahlia tubers are meant to stay in storage for one dormant season (typically 4 to 6 months). They cannot stay in a box for multiple years; they need to grow, soak up sun, and recharge their energy every summer. If you leave them in storage through the summer, they will eventually dry out and lose the ability to sprout. See this guide to how long dahlia tubers can be stored.
What is the easiest way to tell if a stored tuber is still alive?
A healthy, living tuber should feel firm to the touch, similar to a fresh potato. If you gently squeeze it and it feels hollow, brittle, or very mushy, it is likely no longer viable. In the spring, you should also look for "eyes" or tiny green sprouts starting to form near the neck of the tuber.
