rotting of the bottom end of tomatoes

Blossom end rot on tomatoes. Photo: Brenda Kennedy, University of Kentucky, Bugwood.org

Updated: July 19, 2021

Blossom end rot is a common nutritional disorder of tomato, pepper, eggplant, pumpkin, squash, and watermelon 

Key points 

  • Blossom-end rot (BER) is a common nutritional disorder of tomato, pepper, eggplant, pumpkin, squash, and watermelon that is caused by a shortage of calcium in enlarging fruits.
  • This nutritional disorder typically occurs when plants are growing rapidly and often affects the first developing fruits. Dark blemishes appear on the blossom-end of affected fruits as cells break down. They 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 on pepper
Blossom end rot - peppers

Preventing blossom end rot

  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.

the beginning of blossom end rot on plum tomatoes
As fruit cells breakdown due to a lack of calcium, dark blemishes
appear on the blossom-end of affected fruits