K-State Research and Extension

Q: My neighbor has begun harvesting vegetables already and I don’t seem to have anything but blossoms yet. What’s going on?
A: If you have vegetables that are blooming but not setting fruit, you may have a problem with flower pollination. There are several possible reasons for this that usually vary by species. One condition that can affect several species at the same time is overfertilization. Too much nitrogen causes the plant to emphasize vegetative growth, often to the detriment of fruit production. Overfertilization can lead to a delay in flower production and a decrease in fruit set among the flowers produced. Tomatoes are very sensitive to this. If you have nice, large plants but no fruit, check your fertilization.
Squash, cucumbers, watermelon, and muskmelon can have a couple of other problems. First, the early flowers on these plants are usually all male. The production of both male and female flowers becomes more balanced as time passes. You can easily tell the difference between the two because only the female flower has a tiny fruit behind the blossom. If you have both, have not overfertilized. You still have a problem, so make sure you have pollinators. Look for the presence of bees visiting the plants. If you don’t see any, try hand-pollinating several flowers. Use a painter’s brush to transfer pollen from the anther of the male flower to the stigma of the female flower. If you get fruit on only those flowers you pollinated, you need more pollinators.
Make sure you aren’t killing the pollinators with overuse of insecticides. Tomatoes are wind pollinated and therefore not dependent on pollinators. Another possible problem is temperature. Tomatoes normally won’t set if the night temperature is below 50 due to sparse pollen production. This, of course, is only a problem early in the season. However, they also won’t set when nighttime temperatures are above 75 degrees F and daytime temperatures are above 95 degrees F with dry, hot winds.