Managing weather-related problems in vegetable garden

AMES — Not all problems in the vegetable garden are caused by insect pests or diseases. Hot temperatures and heavy or inconsistent rainfall can lead to deformed fruit and low yields.

According to Aaron Steil, consumer horticulture extension specialist, high temperatures, particularly those above 90°F during the day or 75°F at night, can cause blossom drop in crops such as tomatoes, peppers and green beans. Flowers may fail to form or fall off before pollination, leading to reduced yields.

“Temperatures above 85°F can delay ripening in vegetables like tomatoes, peppers and eggplant, causing fruit to remain green longer. Cool-season crops like lettuce, spinach and peas often stop growing altogether,” said Steil.

“While soil is typically cooler than the air temperature, if it exceeds 86°F, potato tubers stop forming. Heat also causes incomplete or poor pollination in vine crops like cucumbers and squash, resulting in misshapen produce.”

Flavor is also affected by hot weather. Cucumbers may taste bitter, and crops like melons and carrots may have reduced sweetness as sugars are used at a higher rate in the heat, Steil said.

Managing heat stress in crops is challenging, but Steil recommends deep weekly watering when conditions are dry to reduce plant stress and promote deep, resilient roots. Adding a layer of mulch helps lower soil temperatures and reduces water lost to evaporation.

Heavy or inconsistent rainfall can also cause problems in the vegetable garden.

“Tomatoes, particularly large-fruited varieties, may crack from rapid growth, especially under high temperatures and direct sunlight,” said Steil. “Cabbage heads can split after heavy rainfall as excess water creates internal pressure from quick uptake.”

Inconsistent rainfall can lead to blossom end rot in tomatoes, peppers and summer squash. This begins with a brown or black spot on the fruit's blossom end (bottom) because of a calcium deficiency.

“The deficiency is caused by wide fluctuations in soil moisture, which impairs calcium uptake by the roots, Steil said. “Secondary infections follow, causing the fruit to rot.”

While rainfall cannot be controlled, consistent soil moisture can reduce these issues. During dry periods, water deeply once a week. Mulch can also help reduce evaporation from the soil surface. If fruit shows signs of blossom end rot, discard it.

Damaged produce with no signs of decay is still edible, but ensure it is used or processed quickly, as it will not store well.