One of the great things about summer is growing fresh tomatoes. It is also among summer’s gardening challenges because tomatoes prefer mild temperatures in the 70s to mid 80s. Hot temperatures can cause an otherwise healthy tomato plant to quit bearing fruit in mid-summer, or the plants can be shy about setting fruit when summer bears down hard.
Throughout the state, the average summer highs are nearly 90 F, with plenty of days that push higher. When daytime temperatures are above 90 F and night temperatures above 70 F, pollination and fruit set on tomatoes are compromised. This is due to the physiology of the plant, and most gardeners find blossom booster spray (a fruit- setting hormone) doesn’t help much in the heat.
Thankfully, plant breeders have been working on a fix: heat-tolerant tomato varieties sometimes called “heat-set” types that are better about setting fruit in hot weather. These will behave even when the temperature is in the low to mid 90s. Their names include Heatwave, SunMaster, Sure Fire, Florida 91, Heatmaster, Phoenix, Solar Fire and Summer Set. They are all hybrids of medium to large, red, round slicing types. They can be planted now and later in the summer for a fall crop.
Plants can be started from seed now, or purchase the biggest plants available. This time of year, garden centers often carry plants in 3-gallon containers. These have a root system big enough to help handle the demand for water in Alabama heat until the roots grow in a new location. Handle them gingerly when transplanting from a nursery pot into the ground or larger container. If the nursery pot is not too thick, it may be easier to cut the pot away from the roots with a utility knife.
No matter what tomatoes are in the garden, be patient if they pause in the heat this summer. Keep plants watered and healthy so they can begin bearing again as soon as the weather cooperates. Bite-sized tomatoes don’t seem as bothered by the heat. Some popular cherry and grape varieties include Sweet Million, Sweet 100, Super Sweet 100, Sungold, SunSugar, Grape, Black Cherry, Chocolate Cherry and Yellow Pear.
If unproductive plants are under a strong patio light that stays on all night, the continuous illumination may be affecting the plant’s ability to set fruit. Virginia Tech reports that fruit set can be retarded under continuous light.
Even though it’s June, there is still time to plant and enjoy tomatoes. Start with the heat-set or cherry types and enjoy a great harvest in late summer and into fall.