Table of Contents
- Introduction
- Understanding the Dahlia Lifecycle
- Perennial vs. Annual: How Dahlias Compare
- The Role of Hardiness Zones
- When to Expect Your Dahlias to Return
- How to Help Dahlias Survive the Winter in the Ground
- The Step-by-Step Guide to Digging and Storing
- Why Some Dahlias Don't Come Back
- Dividing Your Dahlias: Growing More for Free
- Preparing for Spring Replanting
- Starting Fresh: When to Buy New Tubers
- Managing Pests and Growth as They Return
- Dahlias in Containers
- The Long-Term Beauty of Dahlias
- Conclusion
- FAQ
Introduction
There is nothing quite like the feeling of seeing your first dahlia bloom of the season. These spectacular flowers offer an incredible range of colors and shapes, from tiny pom-poms to massive dinnerplate varieties. Many gardeners fall in love with their late-summer beauty and immediately wonder if they can enjoy the same plants again next year. At Longfield Gardens, we believe every gardener should experience the reward of watching these stunning flowers return season after season.
The short answer is that dahlias are perennials, but they are "tender" perennials. This means they can live for many years, but they do not like the cold. Whether your dahlias grow back on their own or need a little help from you depends mostly on your local weather.
In this guide, we will explain how to ensure your dahlias return to your garden. We will cover how climate affects their lifespan and the simple steps you can take to protect them during the winter months. By understanding a few basic rules, you can turn a single season of color into a lifetime of beautiful blooms. If you're ready to shop, start with our dahlia collections.
Understanding the Dahlia Lifecycle
Dahlias are unique plants that grow from underground structures called dahlia tubers. These tubers look a bit like a bunch of sweet potatoes. They act as a storage system for the plant, holding all the energy and nutrients needed to grow tall stems and heavy flowers. Because the energy is stored underground, the plant has the potential to grow back every year.
In their native home of Mexico and Central America, dahlias grow in a cycle that matches the weather. They sprout when the rains arrive and go dormant when the weather turns dry or cool. In a home garden, we replicate this cycle by allowing the plants to rest during the winter. This resting phase, or dormancy, is essential for the plant's long-term health.
When a dahlia goes dormant, the parts of the plant above the ground will turn brown and die back. This is a natural part of the process. While the stems may look finished, the tubers underground are still very much alive. As long as those tubers stay healthy and do not freeze or rot, they are ready to produce a brand-new plant when spring returns.
Perennial vs. Annual: How Dahlias Compare
In the gardening world, plants are usually divided into two groups: annuals and perennials. Annuals live for only one growing season and then die completely. Perennials are plants that live for three years or more. Dahlias fall into the perennial category, but with a specific distinction: they are "tender perennials."
A hardy perennial, like a hosta or a peony, can stay in the frozen ground all winter and sprout again in spring without any help. A tender perennial like the dahlia lacks the "antifreeze" properties of hardy plants. If the ground freezes where the tubers are located, the water inside the tuber expands and destroys the plant cells. This causes the tuber to turn into a soft, mushy mess that cannot grow back.
Because of this sensitivity, many gardeners in cold climates treat dahlias like annuals. They plant them in the spring, enjoy the flowers all summer, and let them go when winter arrives. However, you do not have to let them go. With a little bit of effort, you can save those tubers and replant them. This makes dahlias one of the best investments for your garden, as a single tuber can provide flowers for a decade or more.
The Role of Hardiness Zones
To decide if your dahlias will grow back on their own, you need to know your USDA hardiness zone. These zones are based on the lowest average winter temperature in your area. You can find your zone by looking at our Hardiness Zone Map.
Zones 8 and Warmer
If you live in USDA zone 8, 9, 10, or 11, your dahlias are very likely to grow back each year without being moved. In these regions, the ground rarely freezes deep enough to reach the tubers. You can simply leave them in the garden. In the spring, you will see new green shoots pushing through the soil as the weather warms up.
Zone 7 and Colder
If you live in USDA zone 7 or lower, the winter temperatures are usually cold enough to freeze the soil. In these areas, dahlias will not grow back unless you take action. For a step-by-step guide, see our How to Lift and Store Dahlia Bulbs.
When to Expect Your Dahlias to Return
If you live in a warm climate or have replanted your stored tubers, timing is everything. Dahlias are not fans of cold soil. They prefer to wait until the ground is consistently warm before they start their growth.
In most parts of the country, this means you won't see growth until late spring or early summer. If you left your tubers in the ground in a warm zone, they might begin to sprout in April or May. If you are planting stored tubers, we recommend waiting until the danger of frost has passed and the soil is about 60°F. If you need planting instructions, see our How to Plant Dahlias.
Once the tubers start growing, they move quickly. You will see a small green "eye" or sprout first, followed by sturdy leaves. From that point, it usually takes about 90 to 100 days for the first flower to appear. Because they grow back from a tuber rather than a tiny seed, they have a "head start" that allows them to reach heights of four or five feet in just one season.
How to Help Dahlias Survive the Winter in the Ground
If you live in a border-line zone like zone 7 or 8, you can increase the chances of your dahlias growing back by giving them some extra protection. This is often called winter storage for tender bulbs and tubers.
The most important step is to provide insulation. After the first frost kills the top of the plant, cut the stems down to about three or four inches. Then, cover the entire area with a thick layer of mulch. You can use straw, shredded leaves, or wood chips. A layer that is 6 or 8 inches deep acts like a warm blanket for the tubers.
Another critical factor is drainage. Drainage refers to how fast water leaves the soil. Dahlias hate sitting in cold, soggy dirt. Tubers are much more likely to rot in wet winter soil than they are to die from the cold. If your garden has heavy clay soil that stays wet, it is often safer to dig the tubers up, even if your climate is relatively warm.
Key Takeaway: In warm climates, dahlias return easily if the soil stays dry and frost-free. Use a thick layer of mulch to protect them from occasional cold snaps.
The Step-by-Step Guide to Digging and Storing
For those in colder climates, digging up tubers is the only way to ensure they grow back. While it sounds like a lot of work, the process is quite simple and can be done in a single afternoon.
Step 1: Wait for the First Frost
Do not be in a rush to dig up your dahlias. The tubers do a lot of their growing and energy storage in the cool days of autumn. Wait until a hard frost has turned the foliage black or brown. After this happens, wait about a week. This short waiting period tells the tuber it is time to go to sleep for the winter.
Step 2: Cut Back the Stems
Use a pair of clean garden pruners to cut the stems. Leave about 4 to 6 inches of stem sticking out of the ground. This "handle" will make it easier to find the clump and give you something to hold onto as you lift it.
Step 3: Dig Carefully
Dahlia tubers grow outward from the center. To avoid slicing through them, start your shovel or garden fork about 12 inches away from the stem. Gently loosen the soil all the way around the plant before trying to lift it. Lift the whole clump out of the ground and shake off the excess dirt.
Step 4: Clean and Dry
Wash the remaining soil off the tubers with a gentle stream of water from a garden hose. This helps you see any damage and prevents soil-borne diseases from traveling into storage. Once they are clean, let the tubers dry in a shaded, frost-free area for one to three days. This "curing" process toughens the skin so they don't rot in storage.
Step 5: Pack Away
Store your tubers in a breathable container like a cardboard box or a plastic bin with holes. Surround them with a medium that holds just a tiny bit of moisture, such as peat moss, vermiculite, or pine shavings. Store the box in a cool, dark place that stays between 40°F and 50°F. An unheated basement or a crawlspace is usually perfect.
Why Some Dahlias Don't Come Back
It can be disappointing when a favorite plant doesn't return, but there is usually a simple reason. Understanding these factors can help you succeed next time.
The most common reason for failure is rot. This happens when the tubers get too wet during their dormant period. Whether they are in the ground or in a storage box, they need to stay relatively dry. If you are storing them, check them once a month. If they look shriveled, mist them with a tiny bit of water. If they feel soft or mushy, remove the affected parts immediately.
Another reason is freezing. If the storage area gets below 32°F, the tubers will die. On the other hand, if the storage area is too warm (above 60°F), the tubers might think it is spring and try to sprout too early. They will use up all their energy in the dark and won't have enough left to grow when you finally plant them.
Lastly, some tubers simply reach the end of their natural life if they aren't divided. A dahlia clump that grows too large can become crowded and lose its vigor. Dividing your clumps every few years keeps the plants young and energetic.
Dividing Your Dahlias: Growing More for Free
One of the most exciting parts of growing dahlias is that they multiply. A single tuber planted in May will usually become a clump of five to ten tubers by October. This means that if you save your tubers, you will have more plants every single year.
Dividing is the process of cutting that clump into individual tubers. Each new piece must have an "eye" to grow back. The eye is a small bump located on the "neck" of the tuber, where it connects to the main stem. It looks very similar to the eye on a potato.
You can divide your tubers in the fall before you store them, or in the spring before you plant them. Many beginners find it easier to wait until spring because the eyes start to swell and turn pink, making them much easier to see. Use a sharp, clean knife to make your cuts. As long as each tuber has a body, a neck, and an eye, it will grow back into a full-sized plant.
Preparing for Spring Replanting
When the birds start singing and the grass begins to turn green, it is time to check on your stored dahlias. This is the moment when all your winter work pays off.
Take your tubers out of their storage boxes about two to four weeks before your last frost date. Inspect them one last time. It is normal for them to look a little bit wrinkled, like a potato in a pantry. As long as they are firm and have a visible eye, they are ready to go.
Some gardeners like to "pre-sprout" their dahlias. To do this, place the tubers in a shallow tray of moist potting soil in a warm, bright room. This wakes the plant up and encourages roots to start forming. By the time the weather is warm enough to plant them outside, you will already have a small green plant. This can give you flowers up to three weeks earlier than planting dry tubers directly into the garden.
What to do next:
- Check your local frost dates to plan your planting time.
- Prepare your garden beds with compost to provide nutrients.
- Ensure you have stakes ready for tall varieties.
- Inspect your stored tubers for any signs of early sprouting.
Starting Fresh: When to Buy New Tubers
Even though dahlias can grow back, there are many reasons why you might want to start fresh with new tubers from Longfield Gardens. Sometimes a winter is unexpectedly harsh, or perhaps you simply want to try a new color palette in your garden.
Buying new tubers is a great way to ensure you are starting with healthy, high-quality stock. We work with experienced growers to provide tubers that are guaranteed to be true to their variety and ready to perform. If you are a beginner, starting with fresh tubers is often the easiest way to learn the ropes before you try the overwintering process.
New tubers also give you the chance to explore different flower forms, including single dahlias. If you grew tall "cactus" types last year, you might want to try a cactus dahlia like My Love. These shorter varieties stay under two feet tall and are perfect for the front of a flower bed or in containers. They are just as likely to grow back as the big ones, making them a versatile addition to any yard.
Managing Pests and Growth as They Return
When your dahlias start growing back, they are at their most vulnerable. New green shoots are like candy to garden pests like slugs and snails. Because the plant is small, a few hungry slugs can eat the entire sprout overnight.
To ensure your dahlias make a strong comeback, keep a close eye on the soil as they emerge. Using organic slug bait or simple physical barriers can protect the tender new growth. Once the plant is about a foot tall, it becomes much tougher and can usually handle a bit of insect nibbling without any trouble.
As the plants grow, remember the "right plant, right place" rule. If your dahlias grew back but didn't bloom well last year, they might need more sun. Most dahlias need at least six to eight hours of direct sunlight to produce those famous flowers. If they are in the shade, they will grow tall and spindly but won't have the energy to create big blooms. For more support tips, see our How to Pinch and Stake Dahlias.
Dahlias in Containers
Can dahlias in pots grow back each year? Absolutely. In many ways, growing dahlias in containers makes the overwintering process even easier. For a compact option, try these border dahlias.
If you live in a warm zone, you can leave the pots outside. If you live in a cold zone, you don't even have to dig the tubers out of the dirt. Once the foliage has died back, simply move the entire pot into a frost-free garage or basement. The soil in the pot acts as an insulator.
In the spring, bring the pot back out into the sun and give it a good drink of water. However, keep in mind that dahlia tubers grow quickly. After a year or two, the clump will become too big for the pot. When this happens, the plant will stop blooming well. Every two years, it is a good idea to tip the pot over, take the clump out, divide it, and replant a single fresh tuber with fresh potting soil.
The Long-Term Beauty of Dahlias
Gardening is a journey, and dahlias are one of the most rewarding companions you can have along the way. There is a special kind of pride in seeing a plant return to your garden year after year. It connects you to past seasons and makes your garden feel more established and personal.
Whether you choose to leave them in the ground or carefully pack them away in boxes, the effort is always worth it. The sight of those massive, colorful blooms in August is a reminder of the cycle of growth and the resilience of nature. With the right care, your dahlias will become a permanent part of your summer tradition.
At Longfield Gardens, we want to help you make these beautiful flowers a success in your yard. Whether you are planting your very first tuber or dividing a prized clump you've had for years, we are here to support your gardening goals. We stand behind our 100% Quality Guarantee.
"Dahlias are nature's way of showing off. By helping them return each year, you are preserving a piece of that beauty for your future self to enjoy."
Conclusion
Dahlias are truly remarkable plants that offer a huge return on a small amount of effort. While they may be tender, their ability to grow back from tubers makes them a favorite for gardeners who value both beauty and longevity. By matching your winter care to your specific hardiness zone, you can ensure that these vibrant stars of the summer garden return to dazzle you again and again.
As you plan your garden, remember these key steps for success:
- Know your zone to decide if tubers can stay in the ground.
- Provide deep mulch and excellent drainage for overwintering.
- Dig and store tubers safely if you live in a cold climate.
- Divide your clumps to keep plants healthy and multiply your collection.
If you are ready to add more color to your life, we invite you to explore our selection of premium dahlia tubers. For shipping details, see our shipping information.
FAQ
Do I have to dig up my dahlias every year?
It depends on where you live. If you are in USDA zone 8 or warmer, you can usually leave them in the ground with a thick layer of mulch for protection. If you are in zone 7 or colder, the tubers will likely freeze and die if left outside, so digging them up is the best way to ensure they grow back.
Will dahlias grow back if the frost kills the leaves?
Yes, a light frost that kills the leaves actually helps the plant! It signals to the tuber that it is time to go dormant and store energy for the winter. As long as the ground itself doesn't freeze deep enough to reach the tubers, the plant will be perfectly fine to grow back the following spring.
How many years will a dahlia tuber live?
Dahlia tubers can live for many years, often a decade or more, if they are properly cared for and divided. Over time, a clump can become "woody" or less productive, which is why dividing the tubers every two to three years is recommended to keep the plants vigorous and blooming heavily.
Can I grow dahlias from the seeds they produce?
You can, but they may not look like the parent plant. Dahlias grown from tubers are clones, so they will always look exactly like the original flower. Dahlias grown from seeds are "surprises" and will often have different colors or shapes. Seed-grown dahlias will also form tubers by the end of their first year, which you can then save to grow that specific new variety again.