My tomato plants are flowering, but aren’t setting fruit. Why?
Unfavorable weather conditions are the primary reason for blossom drop on tomatoes. High daytime temperatures (above 85 degrees Fahrenheit) and low nighttime temperatures (below 55 degrees Fahrenheit) interfere with pollination, causing blossom drop. Optimal growing conditions for tomatoes are daytime temperatures of 70 to 85 degrees Fahrenheit. (Cherry tomatoes set fruit over a wider temperature range than most large-fruited tomato cultivars.) Strong winds and dry soil conditions may also contribute to blossom drop. Strong winds desiccate flowers, while dry soil conditions stress tomato plants.
Nothing can be done about the weather. Deeply water tomato plants once a week during dry weather. Fruit set should increase when temperatures moderate.