Some parts of the country have a different understanding of what the word “hot” means. A hot climate is one where garden retailers regularly throw out the plant care instructions and replace “full sun” with “morning sun,” because very, very few plants can take the blistering heat of a summer’s day in these regions.
With that in mind, we gathered the top performers from four different field trials in undeniably hot climates: South Florida’s Costa Farms; sweltering Louisiana State University; and two Texas sites — Texas A&M University and Dallas Arboretum.
Check out a photo gallery of all the top performers. Also, here are a few notes about weather conditions and trial rules at each site:
“We conduct trials year round that include annuals, perennials and bulbs, with roughly 3,000 entries per year,” says Dallas Arboretum director Jenny Wegley. “This year’s weather has been one for the record books. We had several snow and ice events this winter followed by record breaking rainfall and very little sunshine in the spring. The rain stopped once summer hit and during July and August there were multiple weeks with highs well over 100 degrees. This year we added quite a few vegetables to our trial line up including tomatoes, peppers, squash and watermelon. Our trial gardens are open to the general public that visit the Arboretum, and edibles are always a crowd favorite. We evaluate each entry every two weeks and rate them on a scale of 1-5 in the following areas: leaf color and quality, plant vigor, floral stock display and flowering uniformity. We believe this gives an accurate representation of how the plant performed throughout the season.”
Planting dates: Trials were planted in the field starting in late April for crops like trailing petunias, and through late May for crops like vinca.
Number and kind of entries: More than 500 entries were trialed of more than 70 species. Most were annual bedding plant species, but a significant number of herbaceous perennials were included.
Climate conditions: Conditions cool and wet through May. “We had a record 14 inches of rain in May, which took us over our average annual rainfall for the year,” says Brent Pemberton, Professor and Regents Fellow at Texas A&M. “June continued to be warm and wet. July began a six-week period with no significant rainfall. The latter part of July and the first half of August were very hot and dry. Late August September were seasonably warm, but with long periods between limited rain events. Weather details can be found here.”
“A new approach that I have tried the past couple of years with geraniums, that I have expanded to dahlias, is to put one replication in full sun and two replications under 30% shade,” Pemberton says. “I have found that trialing these two species in shade is more representative of how we would grow these species in this part of the country. For example, plants would be sited with morning sun only or in containers on patios with protection from the heat of the day.”
Louisiana State University
The trials take place at Louisiana State University’s AgCenter at the Hammond Research Station, which is located in Hammond, LA. The gardens experienced excessive rainfall March through early June, but was then followed by July and August with 43 days of 96 degrees or warmer with 0.60 inches rainfall.
Every spring the Costa Farms’ research and development team trials some 500 varieties of annuals, perennials, and tropical plants from plant breeders around the world. All varieties are tested in Miami.
The trial season was relatively dry, with less than 4 inches of rain until late April. Then there was a heavy rainfall of close to 5 inches in less than a week. Temperatures hit the mid to upper 90s around the same time. After mid February, temperatures were primarily in the 80s, with a dip in late March to the low 70s.
You can read more about Costa’s trail detail in its online publication, which also includes some consumer-friendly features like a personality test that links consumers to their ideal garden.