“You know, dahlias won’t grow here” - said many a gardener with good intentions, killing my dreams and causing a minor panic attack, upon my move from Atlanta, GA to Wilmington, NC.
As a garden designer and backyard florist - dahlias are sort of the star of the show from mid summer through late fall in the garden and arrangements. I source and sell dahlia tubers through my gardening business, Hearts and Spade, in effort to share the magic of these beauties with others. There just isn’t another flower that stands up to their hype. They come in every color and hue imaginable and seemingly endless forms, shapes and sizes: from lollipop-like pompons to giant dinner plate-sized blooms. And for all that show, they really don’t ask much.
The first year I planted dahlias it was sort of on accident. A squash borer took out my zucchini plants overnight, and I needed a replacement crop. I ordered a handful of dahlia tubers from 3 Porch Farm on a whim and decided to give ‘em a go. I was richly rewarded for my little investment and enjoyed the most beautiful and prolific blooms from mid-summer until late fall. If I had a penny for every neighbor that stopped in their tracks to ask “What are those flowers?!” …
Safe to say, I was hooked, and wasn’t ready to accept the unsolicited “advice” without digging deeper...
If there’s one thing I've learned from my Master Gardener training it's “right plant, right place”... so is growing dahlias in hot climates an uphill battle? Or worth the effort?
In this post we’ll cover what I learned on my deep dive and through experimenting (when it comes to the garden "when in doubt, test it out" is my motto):
Understanding Dahlias and Heat Stress
Tips for Growing Dahlias in Hot Climates
Top Heat-Resistant Varieties
Understanding Dahlias and Heat Stress
Dahlias are native to Mexico, Central America, and northern South America where they grow in full sun, fertile, well-drained soil, and enjoy warm days and cool nights. Like me, they prefer temperatures around 72 degrees - who can blame them. Here in the sub-tropical climate of coastal NC, we face hot summers and high humidity. While average summer highs climb to 90 in July, it’s the hot nights that really stress plants out. Some dahlia varieties just won’t thrive here without a relief in temps. But some will.
Heat-tolerant dahlia varieties can be grown all over the South - even in Florida!
In order to do so successfully, it’s important to understand more about what these plants want and how to deal with challenges to growing dahlias in hot climates.
How to Grow Dahlias in the South
Select heat-tolerant dahlia varieties
Some of my favorite varieties are listed below - many of these are offered in our shop. There are great resources out there like this article from the Dahlia Society of Georgia, listing a plethora of tested heat-resistant dahlia varieties that grow well in the South. Ball forms seem to have better success overall.
Grow from tubers, not from seed (which are not true to type).
Find the right site
While dahlias love sun, position them in a spot with some afternoon shade to protect them from the scorching southwest sun of hot climates, or consider a shade cloth if shade is not naturally available
Plant at the right time
Toss recommended timelines out the window, and plant when soil temps are around 60 degrees (end of March/beginning of April here in Wilmington)
Mulch
Mulch the ground below dahlias heavily to keep soil cool and moist.
Keep mulch away from directly touching the base of the plant.
Mulch also insulates tubers during winter from freezing temperatures so they can be overwintered in ground (in zones 7 and up)
Mist
Mist dahlia plants on hot days - the evaporating mist helps cool plants
Monitor
Regularly monitor for pests and disease
Avoid fertilizing stressed plants
Don’t fret if plant growth is stunted or flower production slows or halts during the hottest time of the year - as temps cool down, production should pick back up.
Keep plants well watered and don't apply fertilizer when dahlia plants are heat stressed
Water deeply and infrequently
Water deeply and infrequently (~2-3 times a week) for established, in-ground plantings to encourage deep and healthy roots.
If your dahlias are planted in pots or grow bags, water at a higher frequency, making sure the pot does not dry out.
Take rainfall into account and when in doubt, feel it out.. AKA stick your finger in the soil. If it’s dry - water.
***(Note: do NOT water tubers before they sprout - they are very prone to rot and though I’ve read this tip in many a book/article, I have learned this reality the hard way by not heeding this piece of advice)
Harvest regularly
Harvest blooms regularly to keep them blooming
Enjoy and share with friends!
Best Heat-Resistant Dahlia Varieties by Color
Here are a few of my favorite dahlia varieties known to do well in hot climates.
White Dahlias
Red/Maroon Dahlias
Rip City
Cornel
Mingus Alex
Spartacus
Prince Noir
Purple/Lavender
Blackberry Ripple
Peach/Coral
Belle of Barmera
Pink
Otto’s Thrill
Penhill Dark Monarch
Orange
Hamari Gold
Ben Hutson
Ferncliff Copper
This list is in no way exhaustive and there are many great resources out there to be explored. If you’ve had luck growing certain varieties in hot climates - I’d love to know.
Whether you're new to the South, new to dahlias, or not ready to give up on failed attempts - this is your year to grow these gorgeous flowers. By choosing the right varieties, and giving them a little TLC, southern gardeners can enjoy the magic of Dahlias in their own backyard.
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