Summer has been extremely hot in Kit Carson County this year and I have been fielding a lot of calls regarding tomatoes that are not setting on blossoms. Tomatoes do not need a specific day length in order to flower. Temperature is the determining factor. The optimum temperature for fruit set is 65 to 80 degrees F. Wide swings in temperatures from day to night such as we are experiencing (95+ day to 65 night) have an adverse effect on blossom set, sometimes causing plants to drop their blossoms.
Tomatoes, eggplants and peppers are all affected by the high temperatures with a condition called “sticky pollen”. The heat changes the shape of the pollen proteins and makes it difficult for the pollen to leave the anthers (the part of the plant where it is produced). Even though it seems like we have plenty of wind to move pollen around, the plants will do well with a gentle shake from the gardener! The best time to shake your tomatoes, eggplants and peppers is early morning or late evening. Coincidentally this is also the best time to be watering in the garden.
Keep in mind that fruit production in the garden requires more nutrients. Approximately 40 to 50% of the nitrogen requirements for tomatoes can be added to the soil before you even plant the garden. But if your soil is less than 3% organic material, you may need to add nitrogen during the growing season. Now is a good time to feed the garden with a water-soluble nutrient, especially one that includes potassium. Potassium will improve the quality of the produce as well as help the plants better utilize the water you are applying. Follow the instructions on the package for proper application.
Since the fruit is about 95% water, tomatoes use large volumes of water during fruit set. As much as 1.5 to 2 quarts of water per plant per day may be needed from fruit set to harvest! Irregular watering may result in cracked fruit. Mulching and regulated lengths of watering time can help with this important aspect of gardening.
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Article by Lisa Brewer, Colorado Master Gardener