Avoid blossom-end rot on tomatoes

Blossom-end rot is among the most common issues gardeners encounter with homegrown tomatoes. This physiological disorder is characterized by the development of a depressed, brownish, rather dry rot the size of a dime to a half dollar on the blossom-end of the maturing tomato. As the fruit grows larger, so does the affected area until the whole tomato becomes unusable, said a University of Missouri Extension horticulture specialist.

Blossom-end rot is caused by a lack of calcium uptake by the plant. "This does not necessarily mean there is a calcium deficiency in the soil, so application of calcium to the garden often does little to resolve the problem," said Marlin Bates. Most gardeners will notice blossom-end rot when tomato plants begin to produce fruit. The first few weeks of production usually coincide with the onset of hot, humid weather, so the soil's moisture status can swing quite widely. Training and pruning may increase the prevalence of blossom-end rot.

"There are a couple of key practices that can lessen the incidence of blossom-end rot in the garden," said Bates. First, be sure that tomatoes are planted in a loose, well-drained soil to encourage maximum root development. This will help ensure that water and calcium uptake occurs at a sufficient rate. Next, gardeners can slow evaporation of water in the soil by applying a layer of mulch 2 to 3 inches thick around the plants. Finally, when weeding the garden, be sure to avoid cultivating too deeply around the base of the plants. This will help preserve root systems and reduce blossom-end rot symptoms. Remove affected tomatoes so other fruit on the plant will develop normally.

Avoid the use of ammonia fertilizers.