Growing Dahlias in Hot Climates
Will dahlias grow in hot climates?
While I do not personally experience growing dahlias in hot climates, I commonly receive this question: I researched online and also learned some interesting tips from customers… Hope this helps!
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). Many dahlias can indeed be grown in hot places where nights are warm, and there are a few tricks that will increase your odds of dahlia growing success.
My number one tip: 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.
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. Of course, every dahlia variety is different. Thankfully, people are constantly experimenting with varieties, and create 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).
Here is a short list of heat tolerant varieties by Old House Gardens.
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.
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. Also, some people construct a structure to hold shade cloth over their dahlias. It is important to strike a balance between providing your dahlias with enough sun, while providing a little relief from the hottest parts 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, bark, herbicide-free straw, hazelnut shells, sawdust, or leaves will also work well.
Misting Dahlias for Afternoon Heat Relief
Dahlias are said to 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 supposedly will help to cool the plant down.
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. Send your soil into a professional soil testing lab periodically to determine what your soil contains, what it needs, and what amendments to add to make it better.
Some Additional Information
Growing Dahlias in Hot Climates by Growing Kindness
Proof Dahlias Thrive in Heat by Once Upon a Dahlia
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:
Belle of Barmera
Hollyhill Black Beauty (A top performer in a reader’s yard in Mesa AZ!)
Penhill Dark Monarch
Visit my store, here. Dahlia tubers are available March 1st through June (0r until sold out) every year.
Again, do not be afraid to experiment, because not all of the 4,000-5,000+ dahlia varieties in existence have been tested for heat tolerance. Also, please let me know how your dahlias do in the heat! Do you have any advice or resources for growing dahlias in hot climates? Contact me here.