Blossom End Rot
The ends of my tomatoes are turning black. This happens every year. What am I doing wrong?
Blossom end rot causes the damage you describe. It is a common problem caused by a temporary calcium deficiency. Most soils have sufficient calcium. The deficiency often occurs when soil is too wet or too dry and the plant is unable to absorb the needed calcium. The good news is the fruit is still edible. Cut out the blackened portion and enjoy. Reduce the problem by mulching plants to maintain even soil moisture. Always stake or tower the plants at time of planting to avoid root injury. Do not cultivate near plants. This can damage shallow roots, reducing moisture and calcium uptake. Fortunately, the plant usually corrects the problem and the remaining fruit will be fine. If not have a soil test to find out if and how much calcium should be added to the soil.
Photo: David B. Langston, University of Georgia