Watch out for blossom-end rot on your tomatoes

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By Dennis Morgeson


Have you strolled through the tomato patch this summer and out of the corner of your eye you spot that perfectly red ripe tomato?

You then rushed over to pick it only to find that it was rotten on the bottom or blossom end. You are not alone!
Lately I have been receiving calls about this strange disease, as some call it, and what to do about it.
Many want to know what to spray to stop it and many just want to know what is causing it and if they will ever get any tomatoes to eat.
The answer is blossom- end rot and it can occur on many vegetables, but most often it is on tomatoes.
Blossom-end rot is not a disease, and contrary to popular belief and chemical companies, a fungicide is not needed, nor will it work.
It is caused by a lack of calcium in the tomato plant.
When tomatoes grow quickly, or when they have inadequate or fluctuating moisture, they can’t take up enough calcium to support vegetative growth, so they take it out of the tomato fruit skin.
Calcium is an essential part of plant cells, acting kind of like the glue that holds them together.
Without it, the calcium cells pull apart and die, thus causing a black, rotten spot on the fruit.
Most of the time there is plenty of calcium in Central Kentucky soils due to the limestone.  
This means the culprit is generally due to water.
With the high heat and drought, most of us are watering our tomatoes, but generally aren’t doing as good of a job as we thought. (I have had a few blossom- end rotted fruit, too).
The best thing you can do to stop blossom-end rot is to use a soaker hose or other method that will give your tomatoes a slow, deep soaking.
This will allow the plants to have even moisture, and will stop or slow the feast and famine cycle we have provided when watering daily, but never enough to get the plant through without stress.  
You should only need to soak your tomatoes once per week.
If they can’t get through a week, then you haven’t watered enough.
Mulch is another thing that will help.
Mulch slows evaporation and shades the soil, allowing it to hold on to water longer, thus giving the plants an even source of water.
It is also a good idea to have a soil test done just to make sure you don’t have a soil that is low in calcium, which is unlikely.   
Lastly, if you give your plants a weekly dose of water-soluble plant food, you will also be giving it a little dose of calcium, which will also help slow or stop blossom-end rot.
Primarily just giving the plants a constant supply of moisture by watering once per week deeply will take care of the problem.
If you would like to become a Kentucky Master Gardener, give me a call at the extension office at 859-336-7741.
Classes start in September, continuing into November, each Wednesday morning from 9 a.m. until noon.  
Happy Gardening!