Even the best gardeners can still fall short of the perfect red, delicious tomato. Aspects of fertilization, water, and temperature can stand in the way of a perfect tomato.
Failure to set fruit can be caused by a number of problems, including nighttime temperature. Nighttime temperatures outside of a range between 55 and 70 degrees make it difficult for the tomato flower to be pollinated. Also, fruit set is lowest when there are daytime temperatures exceeding 90 degrees.
Other problems include soil that is too dry. Blossoms will dry up and drop. Too much nitrogen produces too much leaf growth at the expense of fruit, flower, and root growth. Failure to ripen can be a temperature issue. Compacted soil, overly wet soil, and low potassium can lead to a failure to ripen.