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Blossom End Rot

End Rot

End Rot

Blossom end rot is a black, sunken area at the blossom end of tomatoes or peppers. The blossom end is the end of the fruit opposite the stem. Blossom end rot is most often seen on green fruits, usually the first fruits to appear on the plant.

Blossom end rot is caused by calcium deficiency in the fruit. That deficiency can be caused by a lack of calcium in the soil or the plant’s inability to draw up calcium from the soil–most often caused by a lack of water. Blossom end rot is aggravated by drought or uneven soil moisture. Soil moisture taken up by plant roots delivers calcium to plant cells or by the excessive application of fertilizer, usually nitrogen or potassium.

Keeping the soil evenly moist, not allowing it to dry out between watering, is the first step to controlling blossom end rot. As well, avoid cultivating too closely to plant roots; damaged roots may not take up water and, in turn, calcium from the soil.

The excessive application of nitrogen or potassium can alter soil chemistry and “lock up” calcium so that it is chemically not available to plant roots. Feeding tomatoes and peppers with compost tea is one of the best ways to make sure plants are well fed but not over-fertilized.

A soil test will tell you if the soil is calcium deficient. If that is the case, add agricultural lime to the soil.

Beside blossom end rot, calcium deficiency results in the die back of growing tips and scorching of new leaves. Calcium deficiency in cabbage and Brussels sprouts will cause internal leaves to brown, in carrots oval pits will form on roots, and in celery leaf growth is stunted.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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  1. Am growing several different varieties of tomatoes and peppers for the first time. I find myself looking for solutions to plant problems on the web and have especially enjoyed the Harvest to Table site.

    • Blossom end rot can result from the inconsistent uptake of water; the soil is dry and then becomes soaked. As well, blossom end rot commonly plagues the first fruits of tomatoes, peppers, eggplants, squash, and melons. Warming soil often solves the problem. Make sure your soil is rich in compost–which is well draining while at the same time moisture retentive. You can add calcium to the soil–calcium helps build strong plant cell walls.

  2. Fantastic. I have not had this problem with my tomatoes before and assumed it was a bug. We are currently in drought conditions and it is difficult to keep up to the watering at the moment. I was just about to give them another top up of nitrogen fertilizer as they are starting to turn red, good timing on finding this article!

  3. Thanks for the info! I have blossom end rot on a couple of my tomato plants (out of 50 plants) and in my case I believe it could have been too much nitrogen fertilizer. I’ve since cut way back and only give a little once a month and all my plants are doing fine now. Whew.

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