09/03/2026
🙁Disappointing or delayed vegetable yields this year?
SDSU Extension Master Gardeners have been fielding many questions this summer about reduced yields in the vegetable garden.
One factor to note is that many parts of South Dakota experienced excessive heat for our area (high heat and and humidity with temperatures above 90°F lasting for at least two to three days).
Hot day and nighttime temperatures can cause flowers to drop. Flower abortion occurs when flowers form but then die and fall off the plant before they can develop into fruit. You may see this in tomato, tomatillo (pictured), vegetables, and other flowering garden plants. Flower abortion can happen at temperatures ranging from 75°F to 95°F.
Pollination is also affected by excessive heat. If flowers are not pollinated, no fruit results. Tomatoes produce new flowers frequently, and these flowers have a 50-hour window in which they can be pollinated. When tomatoes are exposed to sustained hot temperatures (more than 85°F during the day and 70°F at night), the tomato plant's flowers are less likely to be pollinated. During 50-hour periods with hot days and especially hot nights, a round of tomato flowers is likely to drop off without pollination. Green beans can also abort flowers in hot temperatures (over 95°F), especially if the soil is dry.
Did you know that many bees don't like hot temperatures? The ideal range for pollination for many species of bees is between 60°F and 90°F, with hotter temperatures in this range promoting more pollination. Once the temperature reaches 90°F, many bees slow down and pollinate less. You may especially notice this in cucumbers, whose small flowers aren't that attractive to many bees. Have you seen some deformed cucumbers or summer squash this year? These plants may have incomplete or partial pollination - odd and uneven shapes occur when flowers are not fully pollinated.
The good news?
Cooler nights are coming and these will help with tomatoes ripening. The optimum temperature range for tomato maturation is between 68°F and 77°F, while the pigments that turn ripe tomatoes red aren’t produced above 85°F. Once you start to experience some cooler nights, tomatoes will again have several hours within their ideal ripening temperature range, allowing them to fully ripen and redden.
--Another Factor--
Drought can reduce both vegetable yields and quality. Most vegetable crops are 80-95% water, and many have relatively shallow root systems. Most of South Dakota is in drought. Only 11% of South Dakota is classified as drought free. The northeastern corner of the state - from Brown to Roberts counties - seems to have dodged the drought this year. The center of the state, around Pierre, has escaped most of the drought. About 12% of the state is under ‘Extreme Drought.” The entire Black Hills - from Lawrence to Fall River counties -has been under this drought intensity for most of the year. Extreme drought intensity is dotting the rest of the state - from Harding to Corson to Moody counties.
--Suggestions--
🔹Consider using shade cloth to cool vegetable crops. Shade covers help the soil and plants stay a few degrees cooler while also reducing the amount of moisture lost. For most vegetable crops, a 30 to 50 percent shade cloth is recommended. Shade cloth should stay above the plant and should not touch the plant, as that can result in potential leaf burn. Shade cloth can be particularly effective for cool season crops like broccoli, kale, lettuce, and spinach.
🔹Take notes on how your vegetable varieties are performing, and consider trying a new heat-tolerant variety in the future.
🔹Mulching with organic mulches such as straw can keep soil temperatures down and retain moisture.
🔹Water consistently and in early morning if possible.
How Excessive Heat Affects the Vegetable Garden from UMN Extension: https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/yard-and-garden-problems/how-excessive-heat-affects-the-vegetable-garden
📷Hot weather can cause tomatillo flowers to brown and wither and fall off the plant. Photo courtesy of Prairey Walkling
