Are Dahlias Perennials or Annuals? What You Need to Know by Zone
If you’ve ever fallen in love with dahlias and wondered whether you’ll get to enjoy them again next year, the answer depends entirely on where you live. Here’s what you need to know for your zone.
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Dahlias are technically tender perennials, which means whether they return year after year is determined by your climate and USDA hardiness zone. If you have ever wondered whether you need to dig them up each fall or if they can stay in the ground, this guide will walk you through exactly what to do based on your growing zone.
Quick Answer: Are Dahlias Perennials?
- Dahlias are tender perennials.
- They grow as true perennials in USDA hardiness zones 8 through 11, where winters are mild. In colder climates, zones 3 through 7, dahlias are typically grown as annuals unless the tubers are dug up and stored over winter.
If you’re planning to replant or overwinter tubers, I walk through the full process in my post on dividing and storing dahlia tubers.
Are Dahlias Perennials or Annuals?
The short answer is that it depends on your hardiness zone.
Dahlias grow from tuberous roots. These tubers cannot tolerate freezing soil. In warm climates, the tubers survive winter dormancy underground and send up new growth in spring. In colder regions, frozen soil will damage or kill the tubers if they are left in the ground.
This is why dahlias are described as tender perennials. They behave like perennials in warm climates and like annuals in colder ones.
USDA Hardiness Zones Explained
Your USDA hardiness zone tells you the average minimum winter temperature in your area and is the key factor in determining whether dahlias will return the following year.
Dahlias grow well in zones 6 through 11, but they are only reliably winter hardy in zones 8 and warmer.
If you are unsure of your zone, you can look it up using the USDA Hardiness Zone Map by entering your zip code.
Where Dahlias Grow as Perennials (Zones 8–11)
In USDA hardiness zones 8 through 11, dahlias can be grown as perennials. This means the tubers can remain in the ground over winter and return the following spring.
In these warmer climates, the soil does not freeze deeply enough to damage the tubers. Many gardeners successfully leave their dahlias in the ground year after year, especially when soil drainage is good and winters are mild.
However, perennial does not mean maintenance-free.
In warm climates, dahlia tubers tend to multiply quickly and form large clumps. Over time, overcrowding can lead to smaller blooms, weaker stems, and reduced flowering.
Because of this, many experienced gardeners choose to dig up and divide their dahlia tubers every one to three years. Dividing helps rejuvenate the plants, improves airflow, and encourages stronger growth and better blooms.
If you prefer a lower maintenance approach, dahlias can stay in the ground, but it is important to watch for signs of overcrowding or declining flower production. Adding a light layer of mulch during winter and ensuring good drainage will also help protect the tubers.
I garden in zone 10b, and while my dahlias can remain in the ground, I have found that dividing them every couple of years keeps the plants healthier and more productive.
Tip from wendy’s garden:
If your dahlias start producing lots of foliage but fewer flowers, that’s often a sign the tubers are overcrowded. Mark those plants at the end of the season so you remember which clumps to lift and divide next year. It’s an easy way to keep perennial dahlias blooming their best in warm climates.
Where Dahlias Grow as Annuals (Zones 3–7)
In USDA hardiness zones 3 through 7, dahlias are typically grown as annuals.
Winter temperatures in these regions drop low enough to freeze the soil, which can rot or kill dahlia tubers if they are left underground. Because of this, dahlias will not reliably return the following year unless the tubers are dug up and stored.
Many gardeners in colder climates plant fresh tubers each spring and enjoy dahlias for a single growing season.
That said, dahlias can absolutely be grown year after year in cold climates with a little extra effort. Before the first hard frost, allow the foliage to die back, then cut the plants down and carefully lift the tubers. After drying for a few days, the tubers can be stored in a cool, dry place until spring.
When replanted the following season, those same tubers will grow and bloom again. If you would like step by step instructions, I cover the full process in my post about dividing and storing dahlia tubers.
Some gardeners in zone 7 and occasionally zone 6 experiment with leaving tubers in the ground under heavy mulch. Results vary depending on winter severity, soil drainage, and moisture levels. In most cases, lifting and storing tubers is the most reliable option.
Should You Dig Up Dahlias for Winter?
Zones 8–11: Dahlias can stay in the ground, though dividing every few years helps keep plants strong
Zones 3–7: Dahlias should be dug up and stored before winter for reliable regrowth
Whether or not you need to dig up your dahlias depends on your climate.
In zones 8 through 11, tubers can stay in the ground, although dividing every few years improves plant health and flowering.
In zones 3 through 7, tubers should be dug up and stored before winter if you want them to return the following year.
Knowing your zone removes the guesswork and makes caring for dahlias much easier.
How to Grow Dahlias
Types of Dahlias
Dahlias are commonly categorized by their flower shape and bloom size, which makes choosing varieties both fun and a little overwhelming. With thousands of dahlia varieties available, understanding the main types can help you select plants that fit your garden space and design style.
Some of my favorite dahlia types include Dinner Plate Dahlias, Anemone Dahlias, Ball Dahlias, and Star Dahlias. Each brings a different look to the garden, from oversized statement blooms to smaller, more structured flowers.
Other popular dahlia types include single flowered dahlias, waterlily dahlias, collarette dahlias, pompon dahlias, cactus dahlias, decorative dahlias, and fringed or fimbriata dahlias.
If you enjoy learning about specific varieties, the National Dahlia Society is a great resource with detailed information on classifications and cultivars.
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Choosing The Right Dahlia Varieties for Your Garden
When choosing dahlias for your garden, personal preference plays a big role, but there are a few practical considerations that will help set you up for success.
Think about the size of your garden, how much sun it receives, and how you plan to use your dahlias. Whether you are planting for cut flowers, containers, or mixed borders, selecting varieties that fit your space will make growing dahlias much easier.
Dahlia Size
Dahlia size is one of the most important factors to consider when planning your garden.
Depending on the variety, dahlias can range from compact plants around 15 inches tall to towering plants well over six feet. Bloom size also varies widely. Dinner plate dahlias are known for their enormous flowers, which can reach up to 15 inches across, while pompon dahlias produce much smaller blooms closer to one or two inches wide.
Before planting, take a look at the mature height and bloom size listed for each variety and make sure your garden has enough room to support it comfortably.
Dahlia Color
Dahlias come in nearly every color imaginable except true blue and black, and many varieties feature beautiful bi-color or blended petals.
When choosing colors, think about the overall look you want in your garden or flower arrangements. Some gardeners prefer soft, cohesive color palettes, while others enjoy mixing bold shades for a vibrant display.
I tend to gravitate toward pink dahlias, but honestly, it’s hard to go wrong. Choosing colors you love makes the garden feel personal and pulled together.
Tips and Tricks for Choosing Dahlias for Your Garden
Beyond size and color, there are a few additional factors that can help you choose the right dahlias for your space.
Dahlias grow best in full sun and need at least six hours of direct sunlight each day. They also prefer well-draining soil that is rich in organic matter. If your soil tends to stay wet, improving drainage before planting will make a big difference in plant health.
It is also helpful to consider bloom time and plant height so your dahlias work well alongside other plants in your garden. Thoughtful planning at the start leads to stronger plants and more consistent blooms throughout the season.
Where to Buy Your Dahlia Seeds and Tubers
There are many places to purchase dahlia tubers, from large retailers to small specialty farms. I personally love supporting small growers and enjoy the unique varieties they often offer.
One of my favorite sources is Sarah’s Cottage Creations Flower Farm, a family owned farm in Minnesota that releases their dahlia tuber sale once a year, typically toward the end of January.
You can also find quality tubers from larger suppliers such as Swan Island Dahlias, Holland Bulb Farms, and Breck’s.
Wherever you choose to buy, ordering early gives you the best selection.
What Growing Conditions Do Dahlias Need?
Dahlias thrive when they are planted in the right conditions from the start.
They prefer well draining soil that is rich in organic matter, with a soil pH between 6.0 and 7.5.I break down exactly how I prep and amend my beds in my post on the best soil for dahlias. Soil that holds too much moisture can lead to rot, so improving drainage is especially important.
Dahlias are sun loving plants and grow best with six to eight hours of direct sunlight each day. Adequate sun encourages strong stems and abundant blooms.
If you are unsure of your soil pH, a simple soil test can help you determine whether amendments are needed before planting.
tip from wendy’s garden:
If you have no idea what the ph of your garden soil is, you can purchase a soil tester to check it and then amend your soil to get your dahlias off to a great start. I like to add perlite to my soil to improve drainage and keep tubers healthier.
When to Plant Dahlias
Dahlias prefer warm soil and should be planted outdoors after the danger of frost has passed.
In colder climates, wait until your average last frost date before planting tubers in the ground. The Farmer’s Almanac is a helpful tool for estimating last frost dates based on historical data.
Some gardeners choose to start dahlia tubers or seeds indoors or in a greenhouse up to 45 days before the last frost to get a head start on the growing season.
How to Plant Dahlias
Planting Dahlia Seeds
Dahlia seeds can be started indoors using seed trays filled with moist seed starting soil. Make a small indentation in the soil, place the seed inside, and gently cover it.
Keep the soil evenly moist and warm, ideally around 70 degrees. Using a humidity dome or greenhouse cover can help speed germination, which usually occurs within one to two weeks.
Once seedlings grow large enough that their leaves touch, transplant them into larger containers and gradually harden them off before planting outdoors.
Planting Dahlia Tubers
Dahlia tubers should be planted once soil temperatures reach at least 55 degrees.
Dig a hole four to six inches deep and place the tuber horizontally with the eye facing up. Cover it with soil and avoid watering until you see growth above the soil line, as watering too early can cause rot.
Once the plant has sprouted, water deeply and consistently. Drip irrigation or soaker hoses work well for maintaining even moisture.
If you want a full step-by-step with photos, you can read my complete guide to planting dahlia tubers.
Watering and Fertilizing Dahlias
During the growing season, dahlias benefit from regular feeding to support strong growth and abundant blooms.
I prefer using a fish emulsion fertilizer, applied according to the directions on the bottle. Consistent watering is also important, especially during hot or dry weather.
I also share my thoughts on using coffee grounds and other natural fertilizers in this post. Are coffee grounds good for Dahlias.
Mulching around plants helps retain moisture and keeps soil temperatures more stable.
Staking and Supporting Dahlias
Many dahlia varieties grow tall and produce heavy blooms that need support.
Staking plants early helps prevent stems from breaking and improves air circulation. Proper support also keeps plants upright during wind or rain and helps them bloom more efficiently.
Pinching Dahlias for Better Blooms
Pinching dahlias encourages bushier plants and more flowers.
Once the plant reaches about 10 to 12 inches tall, pinch off the top growth on the main stem. This encourages lateral branching and results in more blooms over the course of the season.
Protecting Your Dahlia Flower Plant from Common Pests and Diseases
Common garden pests such as slugs, snails, earwigs, caterpillars, and thrips are often attracted to dahlias.
Healthy plants are more resilient, but regular inspection is important. Early morning is a good time to check for pests. Many can be removed by hand, or controlled with gentle, garden-safe treatments.
Good spacing between plants improves airflow and helps prevent fungal issues. If you notice signs of disease, remove affected leaves promptly and treat as needed.
Having healthy plants is your best defense. However, at times you need a bit of help to keep the pests at bay.
tip from wendy’s garden:
Don’t forget to collect and discard the cut stems and foliage. Properly disposing of any diseased or infested plant material helps prevent the spread of pests or diseases.
Deheading Your Dahlias
Deadheading is an important part of keeping dahlias blooming throughout the season.
Removing spent flowers encourages the plant to produce new blooms instead of putting energy into seed production. Deadheading also keeps plants looking tidy and healthy.
Cut spent blooms back to the point where the flower stem meets a set of leaves. Regular deadheading every few days or weekly, depending on bloom rate, will keep plants flowering consistently.
If you grow dahlias in containers, I share pot-specific tips in my post on deadheading dahlias in pots.
Harvesting Your Dahlias
The best time to cut dahlias for arrangements is early in the morning when temperatures are cool.
After cutting, placing stems in hot water and allowing them to cool can help extend vase life. Refresh vase water daily and add flower food to keep blooms looking their best.
One of my favorite things about growing dahlias is all of the stunning floral arrangements you can create from them.
When to Cut Back Your Dahlias
After flowering has finished and the foliage has died back naturally, it is time to cut plants back.
Wait until after the first frost or until the foliage turns brown. Cut stems back to a few inches above the soil. This allows tubers to finish maturing before winter.
Remove and discard plant debris to help prevent pests and disease from overwintering in the garden.
How to Propagate Dahlias
Dividing Dahlia Tubers
Dahlia tubers can be divided in spring to propagate new plants.
Each division should include at least one visible eye. Allow freshly cut tubers to dry for a few days before planting to reduce the risk of rot.
Dividing tubers not only creates new plants but also helps maintain strong, productive growth.
How to Propagate Dahlias
Dividing Your Tubers
When you are ready to divide your tubers for the spring, be sure to cut each piece with an eye.
Allow each piece to dry for a few days before you plant them.
Other Dahlia Posts from WM Design House
If you love this post, you might also enjoy some of my other posts about growing and caring for dahlias.
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Wrapping Up
Now that you know everything there is to know about Dahlias, I hope you grow some in your garden. They make the most beautiful cut flowers you will enjoy all summer.
Happy planting!
More about me!
Hello, I’m Wendy – a dedicated homemaker with a deep passion for decorating, gardening, cooking, and crafting. I find joy in harmonizing beautiful elements to fashion a space that is both comfortable and inspiring. I will help you create a beautiful home, one project at a time.
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Quick Answer………
- Dahlias are tender perennials. They come back every year in USDA zones 8–11, where winters are mild. In colder climates (zones 3–7), dahlias are grown as annuals unless you dig up and store the tubers over winter.
Love your garden! Your Dahlias are beautiful and I love your planting instructions! Patty Lake
Thank you, Patty. Dahlias are my favorite. I’m glad the instructions are helpful!
They are absolutely gorgeous! I think I will have to give them a try. I am pinning this post so I have the information.
Wendy
I’ve wanted to plant these but just haven’t done so. I’m pinning for future reference.
You will love growing dahlias if you have not tried them before. They make such great-cut flowers to take in the house and enjoy.