KC Gardens

Blossom end rot of tomatoes can be a disappointing surprise

Blossom end rot
Blossom end rot

From Dennis Patton:

The cool May and June has slowed the growth of tomatoes in local gardens. But a few lucky gardeners are starting to harvest tomatoes. Many times the picking of the first ripe tomato of the season turns into a disappointment as these early red fruits have been hit by a problem called blossom end rot.

Fruits afflicted with blossom end rot develop a sunken, leathery lesion on the blossom end or base of the fruit. As the problem progresses it turns black and results in a flattening of the fruit. Often secondary organisms invade the fruit leading to rot.

Blossom end rot is actually a physiological disorder, not an insect or disease. Basically it is a result of weather or environmental patterns. The disorder occurs most commonly during periods of cool and moist or hot, dry weather. I guess we cannot win either way!

The rot results from a shortage of available calcium in the rapidly developing fruits. The problem can happen even though the soil has an abundance of calcium. The disorder is associated with rapid plant growth and quick fluctuations in soil moisture, either too much or too little water. Typically the problem is most severe during periods of hot daytime temperatures, low humidity and windy conditions but it would seem our cooler conditions have led to problems. Over-fertilization can also increase the likelihood of the rot.

The incidence of blossom end rot can be reduced by providing even and adequate soil moisture, especially during fruit set in the spring. Mulching and a balanced irrigation schedule will achieve more uniform soil moisture. Over-fertilization of the plant should be avoided.

The good news is that the environmental disorder normally only effects the first one or two clusters of fruit that develop. After that the plant tends to grow out of the problem. The entire season is not lost, just the prized early tomatoes. Continued good care of the plants should help ensure a bountiful harvest for the rest of the summer. Now if only my tomatoes would ripen, as I am in the mood for a BLT.