Table of Contents
- Introduction
- The Short Answer: Do Dahlias Grow Back?
- Understanding Your Growing Zone
- How to Overwinter Dahlias in the Ground
- When to Dig Up Your Dahlia Tubers
- Step-by-Step Guide to Lifting Dahlias
- Curing Your Tubers for Storage
- How to Divide Dahlia Tubers
- Safe Storage Solutions for Winter
- Checking Your Tubers During the Winter
- Waking Up Dahlias in the Spring
- Simple Tips for Success
- Troubleshooting Common Issues
- Conclusion
- FAQ
Introduction
There is nothing quite like the first time a dahlia opens its petals in your garden. Whether it is a soft pastel Dinnerplate variety or a bright, geometric Ball dahlia, these flowers provide a sense of accomplishment that few other plants can match. At Longfield Gardens, we believe every gardener should experience the joy of seeing these spectacular blooms return season after season.
Dahlias are among the most rewarding flowers you can grow because they offer a high return on your investment. While they are often treated as seasonal highlights, they have the potential to live for many years. This article will explain how to care for your plants so they stay healthy and ready to bloom again. We will cover the basics of hardiness zones, winter storage, and simple ways to multiply your collection.
By understanding a few simple rules about how these plants grow, you can ensure your garden remains vibrant year after year.
The Short Answer: Do Dahlias Grow Back?
The simple answer is yes, dahlias can grow again next year. Botanically speaking, dahlias are perennials. This means they are programmed to live for more than two years. However, because they are native to the warm mountain regions of Mexico, they are sensitive to cold weather.
In many parts of the United States, the ground freezes during the winter. Since dahlias grow from fleshy, potato-like structures called tubers, they are full of water. When the water inside a tuber freezes, it expands and destroys the plant's cells. This causes the tuber to rot once it thaws.
Whether your dahlias grow back on their own or require your help depends on your local climate. In warm regions, they can stay in the ground all year. In colder regions, you simply need to lift the tubers and store them in a frost-free place until spring.
Key Takeaway Dahlias are perennials that can live for many seasons. Their survival through the winter depends on protecting their underground tubers from freezing temperatures.
Understanding Your Growing Zone
To decide how to care for your dahlias, you first need to know your USDA Plant Hardiness Zone. These zones are based on the average minimum winter temperature in your area. You can find your zone by looking at a map or using your zip code on most gardening websites.
In USDA Zones 8 through 11, the ground rarely freezes deep enough to reach dahlia tubers. Gardeners in these areas can usually leave their plants in the ground year-round. A simple layer of mulch is often enough to keep them cozy during a brief cold snap.
In USDA Zones 7 and colder, the winter weather is too harsh for dahlias to survive outdoors. Zone 7 is a "borderline" area where they might survive a mild winter in well-drained soil, but it is safer to dig them up. If you live in Zones 3 through 6, you must lift your tubers every autumn if you want to see them grow again next year.
How to Overwinter Dahlias in the Ground
If you live in a warm climate, letting your dahlias grow again is very easy. You do not need to dig them up every year. Instead, you can focus on protecting the crown of the plant where the stems meet the tubers.
Once the flowers have finished blooming and the foliage begins to yellow in late autumn, cut the stems back. Most gardeners in warm zones cut the stems to about 3 or 4 inches above the soil line. This tidy look makes it easier to manage the garden bed over the winter.
After cutting back the stems, apply a thick layer of mulch. Use materials like wood chips, straw, or shredded leaves. A layer about 4 to 6 inches deep acts like a blanket, keeping the soil temperature stable. This also helps with drainage, which is the way water leaves the soil. Dahlias like to stay relatively dry during their dormant period to prevent rot.
When to Dig Up Your Dahlia Tubers
For gardeners in cold climates, the process of saving dahlia tubers starts with the first frost. You will know it has happened when your vibrant green plants suddenly turn black or dark brown overnight. This might look disappointing, but it is actually a natural signal for the plant.
When the foliage dies back from frost, the plant sends a final burst of energy down into the tubers. This energy is what the plant uses to grow again the following spring. It also helps the skin of the tuber toughen up, which makes it easier to store.
We recommend waiting about a week after the first killing frost before you start digging. This short waiting period allows the tubers to "cure" slightly while still in the soil. However, do not wait too long. You want to get the tubers out of the ground before the soil itself freezes hard. If you have a very wet autumn, you may want to dig sooner to prevent the tubers from sitting in soggy earth.
Step-by-Step Guide to Lifting Dahlias
Lifting dahlia tubers is a straightforward process that requires a little bit of physical effort and a gentle touch. You will need a sturdy shovel or a garden fork. A garden fork is often preferred because it is less likely to slice through the tubers.
- Clear the foliage. Cut the stalks down to about 4 inches above the ground. This gives you a "handle" to hold onto while you work.
- Loosen the soil. Start digging about 12 inches away from the main stem. Dahlia tuber clumps can grow quite wide, and you want to avoid hitting them with your tool.
- Lift gently. Work your way around the plant, loosening the soil on all sides. Gently pry the entire clump upward.
- Remove excess soil. Once the clump is out of the ground, shake it gently. You can use your hands to brush away large chunks of dirt.
- Label your tubers. This is a vital step. Use a waterproof marker to write the variety name directly on the skin of a large tuber, or tie a plastic tag to the stem.
What to Do Next
- Gather your tools: a garden fork, pruning shears, and tags.
- Cut back blackened stalks after the first frost.
- Dig wide circles around the plant to protect the tubers.
- Label every clump immediately so you don't forget the colors.
Curing Your Tubers for Storage
Once the tubers are out of the ground, they need to dry slightly before they go into storage. This process is called curing. If you put soaking wet tubers into a box, they will likely grow mold or rot within weeks.
Find a cool, dry place that is protected from frost. A garage, a shed, or a covered porch works well. Spread the tubers out in a single layer. You can place them on cardboard, newspaper, or in plastic crates.
Let them sit for two to three days. During this time, the skin will firm up, and any remaining soil will dry out. Avoid leaving them in direct sunlight, as this can cause them to shrivel too much. You want them to be dry to the touch, but still feel firm like a fresh potato. If the tubers feel soft or squishy, they may already have rot and should be discarded.
How to Divide Dahlia Tubers
One of the most exciting parts of growing dahlias is that one tuber planted in the spring usually turns into a large clump by autumn. You can divide this clump into several individual tubers. Each one of these can grow into a brand-new plant next year.
To successfully divide a tuber, it must have three things: a "body," a "neck," and an "eye." The body is the fat part of the tuber that holds the energy. The neck is the thin part that connects the body to the old stem. The eye is a small bump or bud located on the "crown" (the area where the neck meets the stem).
The eye is where the new growth will start in the spring. If a tuber does not have an eye, it will never sprout, no matter how healthy the rest of it looks. Many gardeners at Longfield Gardens find it easiest to divide tubers in the spring when the eyes start to swell and become easier to see. However, you can also do it in the autumn to save storage space. Use a sharp, clean pair of snips or a knife to make your cuts.
Safe Storage Solutions for Winter
The goal of winter storage is to keep the tubers dormant, cool, and just moist enough that they do not turn into shriveled raisins. The ideal temperature for storage is between 40°F and 50°F. If the temperature drops below freezing, the tubers will die. If it stays too warm, they may try to grow too early or rot.
There are several ways to pack your tubers for the winter:
- Cardboard boxes or plastic bins: These are easy to find and stack. If using plastic, keep the lid slightly ajar to allow for air circulation.
- Packing material: Surround your tubers with slightly damp peat moss, vermiculite, or sawdust. This helps maintain a stable level of humidity.
- Plastic bags: Some gardeners use "breathable" bags or keep standard plastic bags open at the top.
- Newspaper wrap: You can wrap individual tubers in several layers of newspaper and tuck them into a crate.
Avoid using airtight containers. Tubers are living things that need a tiny bit of oxygen to stay healthy during their sleep.
Checking Your Tubers During the Winter
Storing dahlias is not a "set it and forget it" task. We recommend checking on your stored tubers once a month. This allows you to catch any issues before they spread to the whole collection.
When you check your tubers, look for two main things: rot and dehydration. If you find a tuber that is soft, smelly, or covered in fuzzy mold, remove it immediately. This prevents the rot from jumping 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 material with water to add some moisture back into the air. Do not soak the tubers; just a light spray is enough. If the packing material feels very wet or you see condensation on the sides of a plastic bin, leave the top off for a few days to let it dry out.
Waking Up Dahlias in the Spring
When the days start to get longer and the danger of hard frost passes, it is time to get your dahlias ready for the garden. This usually happens in April or May, depending on where you live.
About four weeks before your last expected frost date, move your tubers to a warmer spot. This "wakes them up" and encourages the eyes to start sprouting. You can even plant them in pots filled with potting soil and keep them in a sunny window or a greenhouse. This gives the plants a head start, which often leads to earlier flowers in the summer.
Do not plant your dahlias outdoors until the soil has warmed up to about 60°F. If you plant them in cold, wet soil, they may sit there and rot instead of growing. A good rule of thumb is to plant them at the same time you would plant tomatoes or peppers.
Simple Tips for Success
Growing dahlias successfully year after year comes down to getting a few basics right. Our trial gardens at Longfield Gardens have shown that consistency is more important than complicated tricks.
First, always choose the right spot. Dahlias need at least six to eight hours of direct sunlight to bloom well. They also need soil that drains quickly. If you have heavy clay soil, consider growing your dahlias in raised beds or large containers. For a sturdy cut-flower option, browse our Ball Dahlias collection.
Second, be patient with watering. When you first plant your tubers in the spring, do not water them until you see green sprouts poking through the soil. The tubers have enough moisture stored inside to get started. Adding too much water early on is a common cause of rot. Once the plant is growing vigorously, you can begin regular, deep watering.
Key Takeaway Success with dahlias comes from matching the plant's needs to your environment. Focus on sunlight, drainage, and proper timing to enjoy a spectacular display every year.
Troubleshooting Common Issues
If your dahlias did not grow back as expected, do not be discouraged. Gardening is a learning process, and even experts face challenges. Usually, the reason a dahlia fails to return can be traced back to one of three things.
The most common issue is moisture. If the tubers were too wet during the winter, they likely rotted. If they were too dry, they may have lost the energy needed to sprout. Adjusting your packing material or your monthly check-ins usually fixes this for the following year.
Another common issue is the "blind" tuber. This happens when a tuber is saved but does not have an eye. It might stay firm and look healthy for months, but it will never produce a stem. Always ensure a piece of the crown is attached to your tubers when dividing them.
Finally, keep an eye on pests. In some regions, slugs and snails love the tender new shoots of dahlias in the spring. If your plant seems to disappear as soon as it sprouts, look for silvery trails on the soil. Protecting young plants with simple barriers can help them get established. If you ever need extra reassurance, our 100% Quality Guarantee backs up what we sell.
Conclusion
Dahlias are a true gift to the garden, offering some of the most spectacular colors and forms in the plant world. While they require a bit more attention than a typical shrub, the reward of seeing them grow again next year is well worth the effort. By understanding your zone and following the simple steps for lifting and storing tubers, you can build a collection that lasts for decades.
- Dahlias are perennials that need protection from freezing.
- Dig tubers after the first frost in cold climates.
- Store tubers in a cool, dry place between 40°F and 50°F.
- Divide clumps in spring or autumn to grow your garden for free.
We invite you to explore the many beautiful Dahlia Dinnerplate High Summer Mix varieties available at Longfield Gardens to start your collection. With a little care and the right timing, your dahlias will be the highlight of your landscape every single summer.
- Dahlias are perennials that need protection from freezing.
- Dig tubers after the first frost in cold climates.
- Store tubers in a cool, dry place between 40°F and 50°F.
- Divide clumps in spring or autumn to grow your garden for free.
We invite you to explore the many beautiful Dahlia Collections available at Longfield Gardens to start your collection.
Ready to start your dahlia journey? The best way to learn is by doing. Pick a variety that makes you smile, follow these simple storage steps, and enjoy the magic of watching it return year after year.
For another crowd-pleasing mix, try the Dahlia Assorted Sangria Collection.
FAQ
Can I leave my dahlias in the ground if I live in Zone 7?
Zone 7 is often considered a "swing" zone for dahlias. If your soil is very well-drained and you apply a thick, 6-inch layer of mulch, they may survive a mild winter. However, because winter weather can be unpredictable, most experts recommend digging them up to be safe. If you want the most up-to-date shipping details for new orders, our Shipping Information page is the best place to check.
How do I know if my stored dahlia tubers are dead?
Healthy tubers should feel firm, like a fresh potato or a carrot. If a tuber is soft, squishy, or smells bad, it has rotted and will not grow. If it is extremely shriveled and snaps like a dry twig when you bend it, it has likely dehydrated beyond the point of recovery.
Do I have to wash the dirt off the tubers before storing them?
You do not have to wash them, and many gardeners prefer to leave a little bit of soil on the clump to protect it. However, if your soil is very heavy or wet, washing them makes it easier to inspect for rot and find the eyes. If you do wash them, ensure they are completely dry before putting them in storage.
Why didn't my saved tubers bloom this year?
If your tubers grew leaves but no flowers, they might not be getting enough sun. Dahlias need at least six hours of direct light to produce blooms. It could also be a sign of too much nitrogen in the fertilizer, which encourages leaves over flowers. Switch to a fertilizer with more phosphorus to encourage blooming. For a step-by-step refresher on better flowering, see How to Pinch and Stake Dahlias.