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How to Stop Tomato Bottom Rot

Tomato bottom rot, also called blossom end rot, appears as a black sunken spot on the tomato's end opposite of the stem. This disorder may become disastrous to your tomato crop, with a loss of 50 percent or more of your crop, estimates the Ohio State University Extension. It begins as a small area that looks water-soaked, but gets larger and turns black and leathery. It's not a parasitic organism, but instead a physiologic disorder caused by a low calcium concentration. Stopping the condition involves applying a quick dose of calcium and following with measures you should take each season to prevent bottom rot.

Things You'll Need

  • Calcium chloride solution product
  • Mulch
  • Soil test
  • Fertilizer


    • 1

      Spray the tomato plant foliage with a calcium chloride solution product in the morning or late afternoon about once a week. Follow the specific application instructions provided with the product, especially since calcium chloride is toxic to plants when applied too frequently or excessively.

    • 2

      Water your tomato plants once or twice a week when they are not receiving sufficient rainfall. Water deeply to provide sufficient water. Tomato plants require about 1 inch of moisture per week for sufficient growth.

    • 3

      Add a layer of mulch around your tomato plants to hold in moisture.

    • 4

      Test your soil pH with a pH tester or have your soil analyzed. Purchase a soil test from any garden center or have your local extension office test the soil for you. Aim for a soil pH around 6.5.

    • 5

      Fertilize your tomato plants with a fertilizer based on the results from your soil test. Follow the specific application directions provided with the fertilizer. Do not use a high nitrogen fertilizer; instead use one that has more potassium, such as a 5-5-15. Avoid over-fertilizing, as that can cause additional problems.