I think my tomato plants have Blossom End Rot. How do I get rid of it?

Blossom End Rot is a destructive disorder of tomatoes. It occurs under condition of high water stress and heavy plant load. The first abnormal indication is a small, water-soaked area around the blossom end of the tomato (opposite the stem). This may appear when the fruit is either green or ripening. As the lesion increases in size, it becomes flattened and black. The disorder is not a pathogen and cannot be prevented with chemical treatment. It is the result of poor calcium distribution within the plant, which is in turn the result of fluctuations in soil moisture. To control it, give plants an inch of water per week, fertilize correctly (avoid over fertilization) and consider mulching to stabilize soil moisture.

Fertilizing before planting will get your tomatoes off to a good start. A high phosphorous fertilizer with an analysis of 5-10-5, 4-12-4, or 5-10-10 is recommended. Apply about 1 heaping teaspoon of fertilizer in a 1-foot diameter circle where each plant will be set and mix into the top ½ inch of soil with a rake. Fertilize at this same rate after the first fruits set and once every month afterwards while the fruits are developing until they reach mature size.

Tomatoes may be left on the ground or they may be staked or caged. Leaving plants untrained requires less work and causes more fruit to be produced per plant; however trained plants have cleaner fruits, are easier to pick and do not have losses of fruit due to soil rot.

Whether your tomatoes are trained or not, it is a good idea to mulch around the base of the plant and under the vines which grow along the ground. Corncobs, leaves or peat moss are all suitable mulches and will help eliminate weeds, conserve soil moisture and keep the fruits clean.

An average tomato plant can be expected to produce 8-10 pounds of fruit during the growing season so ten plants are more than adequate for the fresh tomato needs of a family of 4. If there are frost warnings, mature green fruits can be picked and ripened by wrapping them in newspaper and storing them in a dark place at 55-60 degrees F.

The Macomb County MSU Extension Office Hotline provides research-based information to answer consumer questions on trees and shrubs, lawn and garden care, pest identification and management, & soil testing. The hotline is available Monday, Wednesday, & Friday from 9 a.m until 4 p.m. The telephone number is 586-469-5063.