A long, late winter coupled with what seemed like months of rain has finally given way to the hot, humid weather most of us are accustomed to in summer. I don’t look forward to it, but I do know it’s coming. A lot of home veggie gardens got a late start this year. I know I started picking a few ripe tomatoes about two weeks later than last year. Just when they are starting to take off and produce, early summer heat may have something to say about it.
Tomato fruit set is a common problem when temperatures start to rise. The extension office takes many calls from gardeners wondering why the pretty yellow flowers on their tomato plants dry up and fall off, leaving no fruit behind. This is called “blossom drop” and it’s a problem with tomatoes, as well as peppers and eggplant.
When daytime temperatures exceed 85 F and night temperatures exceed 72 F, tomato flowers will abort. A couple of days of these temperatures and blossom drop may not be a problem. But the longer plants are subjected to these temperatures, the longer the effects on the blossoms will last. Nighttime temperatures that exceed 72 have more of an ill effect on blossom drop than daytime temperatures.
The best thing to do in this situation is to keep your plants as healthy as possible. Keep the plants watered well (MULCH!) and keep an eye out for pests — diseases and insects. Diseases and insects are annual occurrences. Even the healthiest vegetable plants become affected when environmental conditions are unfavorable. Healthy plants will survive the heat until temperatures become more favorable for fruit set.
Unfortunately we cannot do anything to change the weather, but we can plan for next year. I always include a few heat-tolerant varieties of tomatoes so I’ll have at least a few bearing plants when temperatures get rough. Heatmaster, Solar Fire, Talladega and Florida 91 are great hybrid varieties to withstand summer heat. Heirloom tomatoes are a little fussier. But again, there are some that will set tomatoes in the heat like Arkansas Traveler, Yellow Pear, San Marzano and Cherokee Purple.
Tomato blossom drop is not the only problem associated with hot weather. The ripening of green tomatoes is also affected. The optimum temperature range for tomatoes to ripen is in the upper-70s to mid-80s. When air temperatures rise too far above this, carotene and lycopene production by the tomato plant starts to slow down. The longer the temperature remains above favorable levels, the longer it will take for a tomato to ripen. Have patience.
A quirk that’s often encountered when rain is scarce is cracking. Some varieties of tomatoes are just more prone to cracking than others — especially cracking around the top of the tomato. Fruit cracking and splitting occurs when the fruit absorbs water and expands at a faster rate than the fruit wall can withstand. This causes the outer skin to split. It occurs most often in rainy periods following an extended dry period, and when temperatures are relatively high. Another reason to mulch and keep the soil evenly moist.
For help on other home and garden questions, call the Master Gardener Horticulture Helpline at 1-877-ALA-GROW (1-877-252-4769) or visit us online at www.aces.edu.