Tomato plants don’t produce as much fruit

Tomato plant stress

Q. Last year, my tomato plants didn’t produce as much fruit as in past years. Why is this and is there anything that I can do about it?

A. There can be several reasons to explain low fruit production:

• Sometimes flowers drop off the plant during periods of fluctuating temperatures. Temperatures above 90 degrees Fahrenheit during the day can cause the blossoms to drop without setting fruit. If evening temperatures fall below 55 degrees, remain above 75 degrees, or if the humidity is too high, blossoms can also drop prematurely.

• Tomatoes are pollinated by wind or insects. During extreme weather conditions, there can be low populations of insects, which will result in low fruit production.

• Shallow watering can stress and weaken tomato plants. Soil kept uniformly moist will promote the development of a large, healthy root system and will result in good fruit production.

• High nitrogen fertilization encourages vegetative growth and can inhibit flower production, resulting in poor fruit set. Low nitrogen produces spindly vines that cannot support proper plant development.

• Fungal problems, such as early blight and Septoria leaf spot, can also prevent high yields as well as high quality fruit, especially during seasons with periods of heavy rainfall. Gardeners may need to apply fungicide sprays if these diseases threaten to severely defoliate plants. Contact Plant Information Service at (847) 835-0972 or plantinfo@chicagobotanic.org to request a list of approved fungicides.