Growing Dahlias in Hot Climates

Can dahlias be grown in hot climates?

Dahlias originated in the mountains of Mexico and Central America, where summer days are warm and nights are cool. This is why dahlias do best in USDA Zones 4-7 (as well as on the West Coast where summer nights are typically cooler). Dahlias can indeed be grown in hot places where nights are warm, but there are a few tricks.

Experiment!

In this post, I share some tips and tricks to help you be successful. However, do not be afraid to experiment with different combinations of practices, varieties, and planting locations. If misting dahlias during the day sounds like too much work, don’t let that stop you from planting and experimenting.

'Fidalgo Julie' is an example of a tested dahlia variety for growing in hot climates

‘Fidalgo Julie’

Start with Heat Tolerant Dahlia Varieties

The first thing you can do to ensure dahlia success in hot climates is start with heat tolerant dahlia varieties. Some varieties of dahlias can simply handle the heat a bit better than others. Every dahlia variety is different. Thankfully, people have been experimenting with varieties and putting together lists to help future hot-weather dahlia enthusiasts succeed.

The best list of heat tolerant dahlia varieties is put together by the Dahlia Society of Georgia. They offer two different lists in PDF form:
The first is sorted alphabetically.
The second list is sorted by bloom size.
(The Dahlia Society of Georgia also offers a Dahlia Growing Guide for Southern Gardeners).

Old House Gardens also has an abridged list of heat tolerant varieties.

Sad that a dahlia you want to grow is not on any of these lists? Keep in mind, not all dahlia varieties have been tested for heat tolerance. There are an estimated 4,000-5,000 dahlia varieties currently alive and maintained. More are being bred by professionals and home gardeners every year. This means that just because a variety is not on a “heat tolerant” list, it does not mean it is not heat tolerant… It simply may not have been tested for heat tolerance yet. Consider doing your own experiments and sharing the results with others.

‘Valley Porcupine’

Microclimate

If you live in a place with warm nights (over 70 degrees Fahrenheit), pay close attention to where you plant your dahlias. Different parts of your yard will be cooler at night than others. Buildings, rocks, and concrete tend to absorb more heat during the day which can increase the surrounding soil temperature at night.

Plant Where There’s Light Afternoon Shade

Dahlias need at least 6 hours of sunlight per day, but prefer 10-12+ hours per day. Some people say that the secret to successful dahlias in hot climates is to plant them where they get a little bit of dappled shade in the hottest part of the day. Some people will even set up a structure to hold shade cloth over their dahlias. It is important to strike a balance between providing your dahlias with enough sun, while giving them some relief from the hottest part of the day.

Mulching Dahlias to Keep Roots Cool

Dahlia’s feeder roots are shallow: usually within the top one inch of the soil. Mulching dahlias in warmer climates can help keep the plant cool. Apply mulch about 2-3 inches deep. Arborist chips are my personal favorite mulch for dahlias. Wood chips, straw, hazelnut shells, or leaves will also work. Avoid bark dust as it can pack tightly and resist water.

Misting Dahlias for Afternoon Heat Relief

Dahlias can benefit from a misting or light shower with the garden hose during the hottest part of the day. Interestingly, the water evaporating from the leaves will help to cool the plant down.

Water Consistently

Of course, a consistent watering schedule will be important when growing dahlias in hot climates. Water deeply and less often, whenever possible. Usually, people water their dahlia garden 1-2 times per week.

Healthy Soil and Balanced Fertility

Finally, the stronger and healthier your dahlias are, the better they will do battling the heat. Fluffy, organic matter-rich soil will hold onto water while allowing sufficient drainage. Dahlias love compost. Keep in mind that too much nitrogen in the soil will lead to giant green plants with fewer blooms, so apply composted manure only in moderation.

Some Additional Information

Growing Dahlias in Hot Climates by Growing Kindness

Proof Dahlias Thrive in Heat by Once Upon a Dahlia

The Dahlia Society of Georgia

For information most relevant to your particular microclimate, consider reaching out to your local Master Gardener program, University Extension, or Garden Club.

Some verified heat-tolerant dahlia varieties I offer:

Alloway Candy
Amorous
Belle of Barmera
Fidalgo Julie
Honka
Penhill Dark Monarch
Penhill Watermelon
Rip City
Spartacus
Urchin
Valley Porcupine

Visit my store, here. Dahlia tubers are available March 1st through June every year. 
Again, do not be afraid to experiment, because not all 4,000-5,000 dahlia varieties in existence have been tested for heat tolerance. Let me know how your dahlias do in the heat! Contact me here.

Happy gardening,

Eve