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Hot night temps delaying tomatoes PDF Print E-mail

By Robert Tigner
UNL Extension Educator
If tomatoes, or other vegetables, are not setting fruit it is likely due to hot night temperatures and humid days.
Tomatoes are wind, not insect pollinated. Tomato plants shed the most pollen between 10 a.m. and 4 p.m. when days are dry and sunny.
Optimum fruit set in tomatoes occurs when night temperatures are between 60 and 70 degrees F.
When night temperatures are lower than 55 degrees or above 75, this interferes with the growth of pollen tubes and fertilization. High daytime temperatures or prolonged humid conditions also reduce tomato fruit set.
If humidity is too low, pollen will be too dry to stick to flower stigmas. If humidity is too high, pollen will not shed readily and pollen grains stick together, resulting in poor pollination. Once night temperatures cool and humidity levels lower, fruit set increases.