– Garth Ruff, OSU Extension Henry County
Blossom end rot. Photo: University of WI fact sheet
This is the time of year when we hear about the bottom of tomatoes rotting, this is actually called blossom-end rot. This is not a disease but a disorder which affects tomato, pepper, squash, and eggplant, and occurs when soil moisture is uneven. It is easily recognized by the flat, leathery, discolored area on the blossom end of the fruit.
Blossom-end rot occurs when there is a calcium deficiency in the blossom-end of the fruit. If demand for calcium exceeds the supply during rapid fruit development, deprived tissues break down, leaving the leathery-looking blossom end to the fruit. It may be due to lack of calcium in the soil; however, this is not usually the case. The real culprit is usually drastic changes in weather (cool to hot) or uneven or extreme soil moisture fluctuations. When these situations are prevalent during fruit development, calcium uptake is limited, or non-existent and blossom end rot can occur.
What is a gardener to do? Avoid wide fluctuations in soil moisture. Calcium sprays for the fruit are sometimes recommended, but are of little value due to poor absorption and movement of the calcium to the fruit. Long term solution is to make sure the pH is at acceptable levels by adding lime to the soil (this fall will be an excellent time to apply lime). Soil test kits are available at the Extension office to help determine your garden nutrient needs. The good news is if the fruit is ripe, the undamaged portion should be fine to eat.