Yard and Garden: When Cucumbers, Tomatoes, Peppers Don't Set Fruit


June 29, 2017, 8:31 am | Richard Jauron, Greg Wallace

AMES, Iowa – Summer is the right time for garden plants to bloom and produce a great harvest, perfect for preparing in the kitchen and enjoying at the dinner table. But when such plants don’t produce fruit, what can a gardener do?

Iowa State University Extension and Outreach horticulturists can answer questions about how to best handle low-producing garden plants. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

My cucumber plants are blooming, but aren’t producing many fruit. Why?

Cucumbers and other vine crops are monoecious. Monoecious plants have separate male and female flowers on the same plant. Male and female flowers are similar in appearance. However, female flowers have small, immature fruits at their base. Pollen is transferred from the male to the female flowers by bees and other pollinators. When properly pollinated and fertilized, the female flowers develop into fruit. The first flowers to appear on cucumbers and other vine crops are predominately male. As a result, fruit production is poor when the vines begin to flower. The cucumber vines should start producing a good crop within a few weeks as the number of female flowers increases.

Poor weather and the use of insecticides also can affect fruit set on cucumbers. Cold, rainy weather during bloom reduces bee activity. Fewer bees visiting the garden results in poor pollination and poor fruit set. Apply insecticides in the garden only when necessary to avoid harming bees and other pollinators.

Tomatoes

My tomato plants are flowering, but aren’t setting fruit. Why?

Unfavorable weather conditions are the primary reason for blossom drop on tomatoes. High daytime temperatures (above 85 degrees Fahrenheit) and low nighttime temperatures (below 55 F) interfere with pollination, causing blossom drop. Optimal growing conditions for tomatoes are daytime temperatures of 70 to 85 F. (Cherry tomatoes set fruit over a wider temperature range than most large-fruited tomato cultivars.) Strong winds and dry soil conditions also may ontribute to blossom drop. Strong winds desiccate flowers, while dry soil conditions stress tomato plants.  

Favorable weather and good care should result in good fruit set. Deeply water tomato plants once a week during dry weather.

Why are my pepper plants blooming but not setting fruit?

Peppers (especially bell peppers) are sensitive to high and low temperatures during bloom. Pollination and fruit set typically don’t occur when daytime temperatures rise above 85 F or when nighttime temperatures drop below 60 F. (Hot peppers tolerate high temperatures much better than bell peppers and often produce well in hot weather.) Dry soil conditions and windy weather during flowering also can inhibit pollination and fruit set.  

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