Answer: If your tomato plants are producing flowers, they're probably healthy enough to produce fruits. The most common reasons for non-fruiting even though they produce flowers is 1) high temperatures (pollen can become sterile in temps over 90F) or 2) lack of insect activity to transfer pollen. Tomato flowers are for the most part self-fertile but the pollen still needs to move from the male to the female parts of the flower. You can try shaking the branch gently when a flower is fully opened.
Best wishes with your tomatoes!
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