University of Maryland Extension

Blossom End Rot - Vegetables

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blossom end rot

Blossom-end rot is a common nutritional disorder of tomato, pepper, eggplant, pumpkin, squash and watermelon that is caused by a shortage of calcium in enlarging fruits. Calcium is taken up constantly by plant roots as a dissolved nutrient and travels first to the growing points- new leaves and shoots. Fruits may experience a shortage of calcium if water becomes less available to plant roots (drought).

This nutritional disorder typically occurs when plants are growing rapidly and the first fruits are developing. As fruit cells breakdown due to a lack of calcium, dark blemishes appear on the blossom-end of affected fruits. These may enlarge until the entire bottom of the fruit becomes dark, shrunken and leathery. Factors that encourage blossom-end rot include low soil pH and low levels of calcium, inconsistent watering, shallow watering or droughty conditions, and excessive use of nitrogen fertilizers. Symptoms are rarely seen in cherry tomatoes and are most often seen in large plum or paste-type tomato cultivars and long pepper fruits.

blossom end rot tomato 
Blossom end rot of tomato

blossom end rot on pepper
Symptoms on pepper


The following steps can be taken to prevent this problem:

  1. Maintain soil pH in the 6.3-6.8 range.
  2. Mix in a handful of ground limestone with the soil from each planting hole prior to transplanting.
  3. Keep plants well mulched and watered through the growing season. Water deeply at least once per week if rainfall is lacking. A mature tomato plant may require 2-3 gallons of water per week.
  4. Avoid high nitrogen fertilizers like ammonium nitrate.

Where symptoms appear, remove fruits immediately. Spraying affected plants with a calcium chloride solution may offer some temporary relief. Regular, deep watering will alleviate the problem if calcium levels in the soil are adequate.

dark blemish of bottom of tomato
As fruit cells breakdown due to
a lack of calcium, dark blemishes
appear on the blossom-end of affected fruits

affected watermelons
Blossom end rot on watermelon

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