Troubleshooting Tomato Plant Problems

Master gardener Paul James tackles one of summer's most puzzling garden problems: why don't my tomato plants set fruit? A tomato plant's failure to set fruit can be caused by several things, but there are some common causes.

Hot weather may be the culprit behind fruitless plants. Although tomatoes are true warm-season crops and need plenty of sunshine to maximize fruit production, temperatures above 85 degrees may cause them to stop flowering. Without flowers, there won't be any fruit.

Blossom drop, where flowers form but drop prematurely, is another reason why tomato plants might not fruit. Blossom drop can be caused by the weather (rainy and cool or hot and dry) or a magnesium deficiency, which can be corrected by either spraying the plant with a seaweed extract or by applying Epsom salts to the soil at a rate of two to three tablespoons per plant. Too much high-nitrogen fertilizer is another fairly common problem, which leads to lots of foliage, but little or no fruit.

Remember, too, that there are two types of tomatoes. Indeterminate types can grow quite tall and produce fruit over a long period of time, and determinate types are much shorter and produce fruit over a much shorter period of time.

"Thankfully, the factors that affect a tomato's ability to set fruit are fairly easy to control, with the exception of weather," Paul says. "And if you provide a tomato plant with everything it needs, such as good soil enriched with plenty of compost and aged manure, lots of sun, and a nice layer of organic mulch, you should have a substantial harvest and plenty of BLTs!"