Are dahlias annual or perennial? The answer depends on what climate you live in!
Dahlias come in myriad colors, shapes and textures. They are a stunning flower that bloom prolifically into late fall when deadheaded properly (read our guide to pruning for blooms here!). Generous and flamboyant, dahlias are a florist favorite and a powerhouse for cutting gardens.
If you are new to growing dahlias, you may be wondering if they are an annual or a perennial.
The answer is nuanced: they can be either, depending on climate. Join us today as we explore how dahlias tend to perform in different zones. We’ll also discuss what you can do to help your dahlia tuber thrive… and even act like a perennial!
Are Dahlias A Perennial? The Short Answer
Dahlias act as a perennial in zones that have a milder winter: zones 8-10. They are treated as an annual in zones 1-7. Because they survive as a perennial only in specific zones, they are considered a tender perennial.
A tender perennial simply means that the plant can act either as an annual or perennial, depending on the conditions in which it is grown. Tender perennials need help to survive zones with cold winters.
You can see what growing zone you live in here.
If you want to find a dahlia acting like a perennial in her native habitat, you’d travel to Central America. Being a heat loving plant, dahlias originally hail from areas such as Mexico and Guatemala, where they bask in the mountain heat and spring to life each year with colorful blooms.
Read our complete guide to growing dahlias right here!
How Climate Affects Dahlia Lifespan
Originating from just 35 species, dahlias are a perennial bloomer in the ideal climate.
If you live in a location that has a moderate climate, you’ll be able to easily grow dahlias as a perennial, though you may need to mulch the ground to ensure the survival of your dahlia tuber during winter months. When cooler weather occurs, the plant will die back, but the tuber will remain healthy in the ground and ready to grow again when temperatures warm up the following year.
If you are growing dahlias in a colder climate, however, cold frosts and snow will kill the dahlia tuber in the ground, making your dahlia an annual.
Continue reading to learn how to care for dahlias in your specific zone.
Overwintering Dahlias By Mulching
If you live in zone 10 or above, you are in luck… your dahlia plant will need no special care to winter over. Dahlias in zone 10 are blessed with just the right climate to thrive.
In zones 8 and 9, you will need to take special care to ensure your dahlias come back, taking steps to overwinter your dahlias in the ground.
First, cut back your plant once frosts begin, then mulch heavily.
How to Mulch Dahlia Plants
Mulching dahlia plants is very simple. Wait until the foliage of the dahlia plant dies back after the first frost in fall. Once this happens, trim your dahlia foliage back to a couple of inches above ground level.
Next, you can add a thick layer of mulch on top of the dahlia tuber to protect the plant.
Best Mulch For Dahlias
A heavy mulch is needed to protect the dahlia plant. This gives a layer of protection between the fleshy tuber from which the dahlia sprouts, and the cold winter frost. You can use wood chips, peat moss, pine needles, or straw. Layer the mulch at least 4 inches thick to protect the dahlia tuber.
A Note From Our Readers: Vicky is an avid dahlia gardener living in zone 8 of Southwest Washington and says; “I have mulched my dahlia plants for years with a thick layer of wood chips. Usually, my dahlias come back. But we do have the occasional hard winter where I lose a few dahlias. Since I love them, I just keep buying and planting more!”
Overwintering Dahlia Tubers
In zones 7 and below, dahlia flowers do not survive winter in the ground. In these zones, a dahlia plant can either be grown as an annual, or the tuber can be removed from the ground and replanted. If you choose to dig up the dahlia tuber, you will essentially be preserving and re planting it, making it a perennial with a little elbow grease. 😉
The tuber resides beneath the dark soil of the dahlia plant. This tuber stores the energy the plant needs every year to grow, thrive, and create a root system.
Unfortunately, the dahlia tuber is just not cut out to survive cold winters. In zones 7 and below, dahlia tubers must be gently removed from the ground and stored for winter.
How To Dig Up And Overwinter Dahlia Tubers:
- Label your dahlia plants well before frost hits so that you know what tuber you are pulling out of the ground. Place your label down near the bottom of the plant so that it is not lost when cutting back. Trust us on this one!
- Once the first frost hits, cut your dahlia back to the ground, leaving 3 to 4 inches of plant in tact. You will want to do this when you are ready to dig up your dahlia tubers.
- Gently dig up the root ball which contains your tuber. To avoid breaking your tuber use a pitch fork instead of a shovel, and gently loosen the soil all around the tuber. Avoid damaging the dahlia tuber as cuts and breaks can make the susceptible to rot.
- Leave your dahlia tuber encased in dirt, and let air dry for a few days.
- Store the dahlia tubers in cardboard boxes that are well ventilated and contain peat moss or growing mix. Overwinter them in a cool, dry place, such as a basement. The goal is to keep the tubers from getting moisture laden and rotting, or from getting dried out. Check on tubers regularly to ensure health.
Overwintering dahlia tubers can be tricky, so go slow and regularly check on your tubers.
It may take some time to get the hang of preserving your dahlias year after year, but doing so can allow you to preserve and re plant your favorite dahlia plants!
Will Dahlias Come Back Every Year?
Dahlias, a delightful flower that come in hundreds of delicious hues, are heat loving and weary of frosts. Because of this, they only come back every year in zones 8 and above.
Zones 8 and 9 require thick mulching to keep dahlia tubers alive. Zones 7 and below require a little work in digging up and overwintering dahlia tubers in a cool, dry place. Dahlias are a generous plant with amazing blooms, so we think the extra work is worth the effort!
Happy planting and enjoy the dirt! – The Green Garden Cottage Crew