Heat Tolerant Dahlias

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I live in the northern part of North Carolina in plant hardiness zone 7b where we have temperatures in the 90's during the summer with nighttime lows in the 70's.  Growing dahlias in the south can be a challenge since the humidity is very high during the summer with dew points in the upper 60's to 70's.  My dahlia field is in full sun with no shade so I grow heat tolerant dahlias.  In 2022, I did add a shade structure over 4 rows that blocked 30% of the sun.  It did make a difference.  The color of the dahlias were more intense and dahlia cultivars that tend to show an immature green center did not under the shade structure.  I do find that dahlias do benefit with afternoon shade if you live where the summers are very hot and humid.

I tried to keep this list of dahlias that I have grown to fully double dahlia varieties that hold their center and keep their form in the summertime when grown in full sun. In our hot summers, some dahlia varieties show a green center or immature center especially in "all day" full sun gardens. The hot temperatures are causing the dahlia to open before the center has time to mature.  Dahlias may change color due to the weather but that does not seem to be such an issue like the green centers or oblong centers.  I grow Jomanda, Sweet Nathalie, Rock Run Ashley, and Bracken Rose; however, they tend to show immature centers for me in my full sun dahlia garden during the hot, humid summer.   In late September, these dahlia varieties hold their form and are beautiful like most dahlias do in the fall with cooler temperatures and the sun is not as intense. I find that some dahlia varieties that are grown where they receive late afternoon shade hold their form throughout the summer when these same dahlia varieties grown in full sun all day do not hold their form.

When growing dahlias in the south for exhibition, growers cut them back in early July so they bloom in late September and October when the weather is cooler.  I do find that ball dahlias do tend to have more of a formal decorative form due to the heat and humidity in my area.

This list is fully double dahlias as anemones, collarettes, orchids, and singles usually do very well in our hot, humid summers.  You do have to keep your dahlias watered weekly if you do not receive any rain. Also, your weather conditions and your soil can affect the growing conditions of dahlias.  Dahlias do like well drained soil with a pH around 6.5 or so.  Try to keep damaging insects under control. If dahlias are under a lot of stress from insect pressure or extreme heat, they can show immature centers and not have a great vase life.

There are thousands of dahlias so it is hard to grow them all; however, this is a list of heat tolerant dahlias that have done well for me in my dahlia garden in northern North Carolina (plant hardiness zone 7b). I tried to keep the list to dahlia varieties that you can find in the American Dahlia Society Composite Listing of Dahlias 1976 – 2022.  I used to sell dahlia blooms to local florists so most of the dahlias that I have grown are for cut flowers.  I just started exhibiting dahlias in September of 2021.  Most of these dahlias bloom within 80 to 90 days from planting and bloom throughout the summer.  If you grow the giant dahlias (AA over 10" across), they are usually late bloomers and take around 120 days to bloom.

20th Ave Ingrid, MB L

20th Ave Memory, BA PK

20th Ave Old Major, BA L

AC Ben, AA SC LB, late bloomer

AC Casper, A ID W

AC Jeri, AA SC Y, late bloomer

AC Tara, BA Y

Amelia Jay, BB SC DP

American Beauty, B ID DR

American Dawn, B FD OR

Belle of Barmara, AA ID DP

Black Satin, BB FD DR

Blizzard, M FD W

Bloomquist Barbara, BB FD Y

Bloomquist Jean, B ID OR

Bloomquist Joel, B LC R, (benefits from afternoon shade)

Blyton Softer Gleam, BA LB

Bonadventure, AA FD BR, (benefits from afternoon shade)

Bracken Rose, BB FD PK, (benefits from afternoon shade)

Bracken Sarah, B FD LB

Brian R, B FD L

Bride To Be, WL W

Camano Buz, MB PK

Camano Zoe, MB PK

Center Court, B FD W

Clearview Blaze, M FD FL

Clearview Butterscotch, M FD LB, (benefits from afternoon shade)

Clearview Daniel, BA Y

Clearview Del Sol, ST Y

Clearview Jonas, A SC LB

Clearview Peachy, BA PK

Clearview Sarah, BB SC W

Clyde's Choice, AA FD OR

Cornel, BA RD, (benefits from afternoon shade)

Cornel Bronze, BA BR

Crazy 4 Ieashia, M FD DR

Crazy 4 Sophie, BB LC DP

Crazy Legs, NX OR

Crazy Smalls, M FD DR

David Howard, BB FD OR

Diva, BB FD PR

Elma Elizabeth, A FD L, late bloomer

Ferncliff Copper, BB FD BR

Ferncliff Spice, MB Y

Gitts Attention, BB ID W

Gitts Crazy, ST DB, late bloomer

Gloriosa, B FD V

Hamari Gold, A ID BR

Hamilton Lillian BB FD OR

Hilltop Lost Treasure, B SC LB, (benefits from afternoon shade)

Hollyhill Black Beauty, BB ID DR

Hollyhill Kris Kringle, BB ID BI

Hollyhill Rudolph, MB R

Hollyhill Taboo, M ID DR

Honeymoon, B ID OR

Innocence, WL PK 

Islander, A ID DP

Jomanda, BB FD OR, (benefits from afternoon shade)

Jersey Beauty, B FD PK

Jessie G, BA PR

KA's Cloud, A ID W

Kelvin Floodlight, AA FD Y, late bloomer

Ketchup & Mustard, A FD FL

Kidd’s Climax, A FD LB

L'Ancresse, BA W

Lavender Ice, M FD L

Little Scottie, P Y

Maarn, BB FD OR

Manor Jubilee, BB ID DR

Miss Amara, BB FD LB

MM Buttercream, BA Y

My Forever, WL OR

Mystique, BB FD DP

Neon Splendor, B ID FL

Nick Sr., AA ID OR, late bloomer

Nicholas BB ID OR, late bloomer

Oh Honey, BA OR

Orange Globe, B FD OR

Pam Howden, WL OR

Parkland Tribute, BB FD DP

Peaches N Cream, M FD BI

Penhill Watermelon, AA ID LB

Rip City, BB ID DR

RobAnn Butterscotch, BB ID LB

Robin Hood, BA DB

Rock Run Ashley, M FD PK,  (benefits from afternoon shade)

Rose Toscano, M FD OR

Sandia Susan, WL OR

Show N Tell, A LC DB

Snoho Doris, BA DB

Snowbound, A ID W

Spartacus, A ID DR

Sugartown Sunrise M FD LB

Sweet Nathalie, BB FD LB, (benefits from afternoon shade)

Sylvia Craig Hunter, B FD OR

Valley Porcupine, NX LB

Valley Rust Bucket, MB BR

Vassio Meggos, A ID L, late bloomer

Verrone's Obsidian, O PR

Verrone’s Sandra J, BB FD OR

Windhaven Blush, A SC Y (benefits from afternoon shade)

Woodland Wild Thing, B SC OR

Zorro, AA ID DR, late bloomer

*Benefits from afternoon shade (in full sun, they can show an immature green center, until temperatures cool down in the fall).