Regardless of the plant, the cause and symptoms are the same. Calcium deficiency results from insufficient calcium in the soil or the inability of plants to absorb enough calcium, Goldberg said. As the weather warms and the plants begin to grow more rapidly, the requirements for water and calcium increase. Blossom-end rot does not spread from one plant to another, Goldberg said. But it can develop in plants grown under the same conditions.
Gardeners can recognize blossom-end rot by the brown discoloration on the blossom end of the fruit.
The spot enlarges as the fruit matures. The lesion tissue becomes sunken and leathery with age. Eventually, secondary fungi or bacteria invade the tissue, resulting in a black or watery appearance. Blossom-end rot is best controlled by following a management program before and after planting. Moderate amounts of additional fertilizer can be used to adjust pH levels enough to keep tomato and pepper plants green and vigorous, but not too lush.