Blossom End Rot - U of I Extension

News Release

Blossom End Rot

This article was originally published on July 9, 2018 and expired on July 16, 2018. It is provided here for archival purposes and may contain dated information.

Growing your own vegetables is fun and rewarding. However, when a perfect tomato or pepper develops a large black end just before picking, gardeners get quite frustrated.

Rhonda Ferree, Horticulture Educator with University of Illinois Extension, explains that blossom-end rot is a common problem on various vegetables, particular tomatoes and peppers. Although it looks like a terrible disease, the problem is related to soil moisture levels, not a disease.

As the name suggests, blossom-end rot develops at or near the bottom (or blossom end) of the fruit and appears as a slight, water-soaked area. Ferree warns that this disorder can be very damaging, with losses of 50% or more in some years.

“On tomatoes, the area enlarges, darkens, and becomes dry, sunken, flat, leathery, and dark brown to black.” Various molds and fruit rots may develop within the sunken area. Pepper, summer squash, and other cucurbit crops may also experience this problem.

 “Blossom-end rot is not a disease, but rather thought to be caused by insufficient calcium when the fruit is forming,” explains Ferree. Calcium deficiency usually results when nitrogen levels are high, when plants grow rapidly, and when extremes in moisture occur (heavy rains, drought, root injury, etc.).

 When soil moisture is limited, plant growth slows, and nutrient uptake by the roots is reduced. If water becomes available again, the plant begins to grow rapidly, but the uptake of calcium lags behind. Thus, the rapidly expanding fruit tip does not have enough calcium available to develop properly, even though there is plenty of calcium in the soil.

  Although there is nothing you can do to help the affected fruit, good horticultural practices can help manage the problem on future fruit.

1.        1. Water your plants consistently with one inch of water per week.

2.        2. Use mulch to maintain more even moisture levels.

3.         3. Maintain the soil pH around 6.5. Use a soil test to determine soil if amendments are needed.

4.         4.  Don’t over fertilize, particularly with nitrogen.

5.         5.  Foliar applications of calcium are not generally recommended.

6.  Do not add Epsom salt, which contains magnesium sulfate. It creates more rot since magnesium and calcium ions compete for uptake into the    plant. The more magnesium in the soil, the less chance that calcium will be absorbed.

For more information on common vegetable crop problems go to


Source: Rhonda J. Ferree, Extension Educator, Horticulture,

Pull date: July 16, 2018