Tomato Problems Related to High Heat

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Tomatoes in basket

When we have high temperatures we can experience problems with vegetable fruit set and quality. Tomatoes are one of the most common plants that we get questions about in the Extension Office.

Daytime temperatures over 90° F and night temperatures over 70° F reduce fruit set in tomatoes. Flowers die and drop due to a lack of pollination or the pollen not being viable.

Another problem with tomatoes during high temperatures is internal white tissue. The white tissue is only noticeable when the fruit is cut. The hard, white areas tend to be in the outer walls of the fruit, although it can also appear in the center of the fruit. High temperatures during the ripening period seem to trigger the symptoms. The darker red varieties are more resistant to this problem.

Blossom end rot is a common problem on tomatoes related to calcium deficiency in the developing fruit. It is most often related to feast and famine when it comes to soil moisture. Blossom end rot is worsened by dry soils that don’t allow the calcium that is present in the soil to be in the soil solution and to be taken up by plant roots. Using an organic mulch can help keep the soil from becoming overly dry and help to reduce the incidence of blossom end rot.

As always, and especially during hot temperatures when you irrigate, make sure the garden soil is wetted to a depth of 6-8 inches. Poke a long-handled screwdriver into the soil until it becomes hard to push. Remove it from the soil and you can measure how deep the soil is wetted. With experience, you will know how long it takes to water your soil to the desired depth, once the top of the soil starts drying out.