Table of Contents
- Introduction
- The Short Answer: Do Dahlias Come Back?
- Understanding Your USDA Zone
- Leaving Dahlias in the Ground (Zones 8–11)
- Lifting Dahlias in Cold Climates (Zones 3–7)
- Cleaning and Prepping for Storage
- The Best Storage Methods
- Mid-Winter Checkups
- Dividing Tubers: Getting More Flowers for Free
- Waking Your Dahlias Up in Spring
- Troubleshooting: Why Didn't They Come Back?
- Conclusion
- FAQ
Introduction
There is nothing quite like the moment a dahlia bud finally unfurls in late summer. Whether it is a giant dinnerplate dahlias variety the size of a dinner plate or a perfectly symmetrical pompon, these flowers are the crown jewels of the garden. Because they provide such a spectacular show of color from midsummer right up until the first frost, it is natural to want that beauty to return every year.
We often get asked by gardeners if their dahlias will come back on their own or if they need to be replanted. At Longfield Gardens, we want to help you enjoy these stunning blooms season after season with PomPon Dahlia. The answer depends mostly on where you live and how you care for the plants once the weather turns cold.
This guide will explain how dahlia tubers behave in different climates and how you can ensure they return even stronger next year. Whether you live in a warm southern state or a chilly northern one, you can keep your favorite dahlias part of your garden for years to come by exploring our dahlia collections. With a few simple steps, your initial investment in these beautiful plants will continue to pay off in abundance.
The Short Answer: Do Dahlias Come Back?
Dahlias are technically perennials, which means they are capable of living for many years. However, they are native to the warm mountain regions of Mexico and Central America. Because of their tropical origins, they have not evolved to survive freezing ground temperatures.
Whether your dahlias "come back" depends entirely on your local winter conditions. In the United States, we use USDA Plant Hardiness Zones to determine which plants can survive the winter in specific areas. These zones are based on the average minimum winter temperature.
For dahlias, the magic number is usually Zone 8. If you live in Zone 8 or warmer, your dahlia tubers can typically stay in the ground all winter and will sprout again when the soil warms up in the spring. If you live in Zone 7 or colder, the frozen soil will likely damage the tubers, meaning they will not return unless you take action to protect them.
Key Takeaway Dahlias are perennials in warm climates (Zones 8–11) but are treated as annuals or "lifted" for storage in colder climates (Zones 3–7).
Understanding Your USDA Zone
Before you decide how to handle your dahlias at the end of the season, it is helpful to know your hardiness zone. Most gardening success comes from matching the plant to the right environment.
- Zones 8 and Higher: These areas include much of the South, the Southwest, and the Pacific Northwest coast. In these regions, the ground rarely freezes deep enough to reach the dahlia tubers.
- Zone 7: This is a "transition" zone. In a mild winter with well-draining soil, dahlias might survive if they are heavily mulched. However, a particularly cold or wet winter can still cause them to rot or freeze.
- Zones 3 through 6: These regions experience deep freezes. In these areas, dahlias must be dug up and stored indoors if you want them to come back next year.
If you are not sure which zone you are in, you can easily find out by checking a hardiness zone map with your zip code. Knowing your zone takes the guesswork out of winter garden prep.
Leaving Dahlias in the Ground (Zones 8–11)
If you are lucky enough to garden in a warm climate, your dahlias can stay right where they are. This is the easiest way to ensure they come back, as the plant stays in its natural environment. However, "leaving them alone" still requires a little bit of autumn maintenance to keep the tubers healthy.
Cut Back the Foliage
Once the first light frost hits, the green leaves of your dahlias will begin to turn brown or black. This is a normal part of the plant’s life cycle. Use clean garden shears to cut the stems down to about 3 or 4 inches above the soil line. Removing the old foliage helps prevent pests and diseases from overwintering near the tubers.
Focus on Drainage
The biggest threat to a dahlia tuber in a warm climate is not usually the cold, but the moisture. Dahlias hate "wet feet." In the winter, dormant tubers are prone to rotting if the soil stays soggy for long periods.
"Drainage" simply means how fast water leaves the soil. If your garden spot tends to collect puddles after a rain, you might want to consider lifting your tubers even if you live in a warm zone. If your soil is sandy or well-drained, your dahlias will be much happier staying put.
Apply a Winter Blanket
Even in warm zones, an unexpected cold snap can happen. Applying a thick layer of mulch acts like a blanket for the soil. Use 4 to 6 inches of wood chips, straw, or shredded leaves over the spot where the dahlias are planted. This mulch regulates the soil temperature and keeps the tubers from experiencing sharp temperature swings.
Lifting Dahlias in Cold Climates (Zones 3–7)
For those of us in cooler regions, keeping dahlias alive through the winter requires a process called "lifting." This simply means digging the tubers out of the garden and moving them to a frost-free spot until spring. While it sounds like a lot of work, it is actually a rewarding part of the gardening cycle that allows you to inspect your plants and prepare for an even bigger display next year.
Timing is Everything
The best time to lift your dahlias is after the first "killing frost." This is a frost that is cold enough to turn the dahlia’s foliage completely black. This frost signals to the plant that it is time to go dormant.
For a fuller walkthrough, see When to Bring Dahlia Bulbs In. After the foliage turns black, it is helpful to wait about a week before digging. During this week, the tubers "cure" in the ground, which helps toughen their skins for storage. If a hard freeze (temperatures consistently below 28°F) is predicted, don't wait—get them out of the ground to keep them safe.
How to Dig Tubers Correctly
Lifting tubers is a gentle process. You want to avoid piercing or snapping the individual tubers, as wounds can lead to rot during storage.
- Cut the stems: Cut the stalks down to about 4 inches above the ground.
- Loosen the soil: Use a garden fork or a shovel. Start digging about 12 inches away from the stem all the way around the plant. This ensures you aren't hitting the tubers, which can grow quite wide underground.
- Lift gently: Pry the entire clump upward. You will likely see a large cluster of tubers that looks a bit like a bunch of sweet potatoes.
- Shake off the dirt: Gently brush away the excess soil with your hands. You don't need to get them perfectly clean yet, but removing the bulk of the mud helps the drying process.
What to Do Next
- Label your tubers immediately using a waterproof marker or garden tape.
- Group varieties together so you don't forget which colors are which.
- Move the clumps to a shaded, frost-free area like a garage or porch for a few days to dry out.
Cleaning and Prepping for Storage
Once your dahlias are out of the ground, they need a little bit of preparation before they go into their winter "sleep." This step ensures they stay healthy and don't succumb to mold or dehydration while they wait for spring.
To Wash or Not to Wash?
There are two schools of thought on washing tubers. Some gardeners prefer to wash all the soil off with a garden hose to inspect for pests or damage. Others prefer to leave a little bit of dry soil on the tubers to provide a natural protective layer.
If your soil is heavy clay, washing them is usually better so you can see what you are working with. If you have sandy soil, a simple brush-off is often enough. If you do wash them, make sure they dry completely before you pack them away. Moisture trapped against the skin of the tuber is the primary cause of rot.
Identifying the "Eyes"
If you want to ensure your dahlias come back, you need to make sure the tubers have "eyes." An eye is a small bump or growth point, much like the eye on a potato. This is where the new sprout will emerge in the spring.
For more about tubers and eyes, read Dahlia Tubers: What You Need to Know. Eyes are located on the "crown" of the tuber, which is the area where the tuber meets the main stem. If a tuber breaks off without a piece of the crown and at least one eye, it will not grow a new plant. When you are prepping your dahlias, be very careful to keep the neck of the tuber—the thin part connecting the body to the stem—intact.
The Best Storage Methods
The goal of winter storage is to keep the tubers in a "Goldilocks" environment: not too cold (which freezes them), not too warm (which wakes them up too early), not too wet (which rots them), and not too dry (which shrivels them).
Choosing the Right Container
You can store dahlia tubers in several types of containers:
- Cardboard boxes: These allow for good air circulation and are very affordable.
- Plastic bins: These hold moisture well, which is great if your storage area is very dry, but you must leave the lids slightly ajar to prevent mold.
- Paper bags: Good for smaller quantities, but they don't offer much protection against temperature swings.
Packing Material
Most gardeners find success by packing their tubers in a "medium" that regulates moisture. Popular choices include:
- Peat moss: Excellent at holding just enough moisture without being "wet."
- Vermiculite: A mineral that provides great insulation and moisture control.
- Wood shavings: Often sold as pet bedding, these are inexpensive and provide good airflow.
Layer the packing material in the bottom of your container, place the tubers inside (not touching each other if possible), and cover them with more material. This prevents one rotten tuber from spreading issues to the rest of the bunch.
The Ideal Storage Spot
Place your containers in a cool, dark place. A temperature between 40°F and 50°F is perfect. Many people use an unheated basement, a crawl space, or a corner of a garage that stays above freezing.
If you use a garage, keep the boxes off the concrete floor, as the cold can seep through. Placing them on a shelf or a wooden pallet is a simple win for tuber safety.
Mid-Winter Checkups
One of the most important steps in making sure your dahlias come back is checking on them once or twice during the winter. It only takes a few minutes, but it can save your entire collection.
Look for Shriveling
If the tubers look wrinkled and feel light, they are losing too much moisture. They are "thirsty." You can fix this by lightly misting the packing material with a spray bottle of water. You don't want to soak them—just a tiny bit of humidity is enough to plump them back up.
Look for Soft Spots
If a tuber feels mushy or looks fuzzy with mold, it has started to rot. Use a clean knife to cut away the affected part, or simply toss that individual tuber in the compost. Removing the problem early prevents it from spreading to the healthy tubers in the box.
Watch the Temperature
If your storage area experiences a sudden cold snap where temperatures drop below freezing, you may need to add an extra blanket over your storage boxes or move them to a slightly warmer room temporarily. Remember, a frozen tuber is a dead tuber.
Dividing Tubers: Getting More Flowers for Free
One of the most exciting things about dahlias is that they don't just come back—they multiply. When you plant one dahlia tuber in the spring, it grows into a large clump by the fall. If you divide this clump, you can turn one plant into three, five, or even ten new plants for the following year.
When to Divide
You can divide your dahlias in the fall right after digging, or in the spring before planting.
- Fall Dividing: This saves space in your storage boxes and the tubers are easier to cut while they are soft. However, it can be harder to see the "eyes" because the plant is dormant.
- Spring Dividing: In the spring, the eyes will begin to swell and turn pink or green, making them very easy to see. The tubers are tougher and harder to cut, but you are less likely to make a mistake.
How to Divide
Use a sharp, clean pair of garden snips or a knife. Cut the clump apart so that every individual tuber remains attached to a piece of the main stem that contains at least one eye. If a tuber breaks off without an eye, it won't grow, so take your time and be precise.
Sharing these extra tubers with neighbors and friends is a wonderful way to spread the joy of gardening. It also ensures that if you have a mishap with your own garden, a friend might have a "backup" of your favorite variety to give back to you.
Waking Your Dahlias Up in Spring
When the days start getting longer and the threat of frost passes, it is time to bring your dahlias out of storage. For a broader refresher on the whole growing cycle, read All About Dahlias. This is the most rewarding part of the process, as you see the first signs of life returning to the tubers you carefully tended all winter.
Pre-Sprouting
You can get a "jump start" on the season by waking your tubers up indoors about 4 to 6 weeks before your last frost date. Place the tubers in a shallow tray of damp potting soil in a warm, bright spot.
Once they sprout green shoots, they are ready to be moved to the garden as soon as the soil is warm. This can result in flowers several weeks earlier than if you planted the dormant tubers directly into the ground.
Planting Out
Wait until the soil temperature reaches about 60°F and there is no more danger of frost. In most parts of the country, this is around the same time you would plant tomatoes.
At Longfield Gardens, we recommend planting dahlia tubers about 4 to 6 inches deep. For more detail on planting depth, see How Deep Should You Plant Dahlia Bulbs?. Place the tuber horizontally in the hole with the eye or sprout facing upward. Cover it with soil and resist the urge to water it until you see the first green shoot emerge from the ground. The tuber has all the energy and moisture it needs to get started on its own.
Troubleshooting: Why Didn't They Come Back?
If you followed the steps but your dahlias didn't return, don't be discouraged. Gardening is a learning process, and even experts lose a few tubers occasionally. Here are the three most common reasons dahlias fail to return:
- Too Much Moisture: This is the number one killer of dahlias. If the soil in your garden is too heavy or if your storage box was too airtight, the tubers will rot. Focus on better drainage or more breathable storage next time.
- Freezing Temperatures: If the ground froze deep enough or the storage area dropped below 32°F, the water inside the tuber turned to ice and destroyed the plant's cells.
- Missing Eyes: If you divided your tubers and they didn't sprout, they likely didn't have an eye. Remember that the tuber is just a battery—the eye is the "on" switch. You need both for the plant to grow.
Every season is a fresh start. If you lose a variety, it is simply an opportunity to try a new color or shape that you haven't grown before, like Dahlia Dinnerplate Islander.
Conclusion
Dahlias are incredibly rewarding plants that offer a level of beauty and variety that few other flowers can match. While they do require a little bit of extra attention in the winter, the process of helping them come back is a satisfying part of the gardener's journey. By understanding your zone, managing moisture, and protecting the tubers from the cold, you can enjoy these spectacular blooms year after year.
Whether you leave them in the ground under a cozy layer of mulch or tuck them away in a box of peat moss in your basement, your dahlias are waiting to dazzle you again next summer. We at Longfield Gardens are here to support you with quality tubers and the practical advice you need for a successful season, plus the big-blooming Dahlia Dinnerplate High Summer Mix.
Next Steps
- Identify your USDA zone so you know whether to mulch or lift.
- Prepare your storage containers and packing material before the first frost.
- Label your plants while they are still in bloom so you know what you are saving.
- Check your stored tubers once a month to ensure they stay healthy until spring.
FAQ
Can I leave dahlias in the ground in Zone 7?
Yes, you can leave dahlias in the ground in Zone 7, but it is a bit of a gamble. To increase their chances of coming back, make sure they are planted in a spot with excellent drainage and cover them with at least 6 inches of mulch. If you have a particularly rare or favorite variety, lifting it for the winter is the safest way to ensure it survives, and next season you might want to try Dahlia Dinnerplate Cloud Nine Collection.
How long do dahlia tubers last in storage?
Dahlia tubers will last through the winter dormancy period, typically 4 to 7 months, depending on your climate. They are not meant to be stored for years at a time. They need the natural cycle of growing in the summer and resting in the winter to remain healthy and viable.
Do I have to water my dahlias while they are in storage?
You should not "water" them in the traditional sense, as this will cause rot. However, you should monitor the humidity. If the tubers look shriveled like a raisin, a light misting of the packing material (not the tuber itself) can help. The goal is to keep them plump but dry to the touch.
What happens if I don't dig up my dahlias in a cold climate?
In Zones 6 and colder, the water inside the dahlia tuber will freeze as the ground temperatures drop. When water freezes, it expands and bursts the plant's cells. Once the ground thaws, the tuber will turn into a soft, mushy pile that cannot grow. In these regions, digging them up is essential if you want them to return.