Blossom end rot

blossom end rotBlossom end rot, or BER for short, is a complex physiological problem that is the result of a calcium (Ca) deficiency. Calcium is not very mobile within the plant and it is required in relatively large amounts when the fruit is rapidly growing. If demand for calcium exceeds supply, tissues lacking this mineral break down leaving a characteristic leathery, brown to black area on the blossom end of fruit such as tomato, pepper, squash, eggplant and watermelon.

Factors leading to the development of BER include:

  1. sharp changes in temperature from cool to hot weather
  2. extreme temperature fluctuation
  3. drought stress
  4. waterlogged soils (i.e. over irrigation or too much rain)
  5. excessive growth due to too much nitrogen fertilization
  6. root damage due to deep cultivation or disease

In Colorado BER normally occurs in the first fruit set of the season.

If BER occurs in tomatoes or other fruit, the solution is often as simple as waiting for temperatures to warm up and evening out irrigation. Otherwise, the following steps may be necessary:

  1. plant tomatoes and other susceptible plants in an area with good drainage; poorly drained soils cause roots to "smother" leading to reduced Ca uptake
  2. avoid wounding roots when hoeing weeds
  3. maintain even soil moisture by using mulches
  4. avoid excess nitrogen fertilizers

For more information, see the following Colorado State University Extension fact sheet(s).

For more information, see the following Planttalk Colorado™ script(s).

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Updated Tuesday, November 19, 2013