Several conditions can cause tomatoes to not set fruit:
- too much nitrogen fertilizer,
- nighttime temperatures over 70 degrees F,
- low temperatures below 50 degrees F,
- irregular watering,
- insects such as thrips, or
- planting the wrong variety may result in poor fruit set.
Any of these conditions can cause poor fruit set, but combinations can cause failures. Tomato plants will also fail to set fruit if they are not planted where they can receive eight to 10 hours of direct sunlight daily. Any less direct sunlight will result in a spindly growing, nonproductive plant with healthy foliage.
