Answer: When a tomato or an eggplant has flowers but no fruit, this is due to one of two issues. The first is lack of sufficient water and the other is a lack of pollination.
When a tomato or an eggplant plant is stressed, its blossoms will dry up and drop off without producing fruit. Your plants need at least 2? of water a week, more in very hot weather. Deep watering encourages olants to grow deep roots, which helps it to find water deeper in the ground which will even out its water needs so it will be less likely to drop flowers.
Both tomato and eggplant flowers are normally wind pollinated, meaning they do not rely on insects like bees and moths for pollination. A pollination problem can occur when the weather conditions are very wet or very humid or are very hot. When the air is very humid, this causes the pollen in the flower to become very sticky and it cannot fall down onto the pistil to pollinate the flower. When the weather is very hot, the pollen becomes inactive because the plant thinks that it cannot support the stress of an additional fruit along with the hot weather. In a sense, the plant aborts the blossom so as not to stress itself further.
If you suspect your tomato and eggplant flowers fall off due to a lack off pollination, then you can hand pollinate. All you need to do is take a small, clean paintbrush and move this around the inside of the flower.
Hope this information is helpful.
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