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What Is the Cause of Blossom-End Rot on Tomatoes and How to Fix it?

Updated: Mar 28

Blossom-End Rot on Tomatoes is something that most gardeners have perhaps experienced at some point, and is not a pleasant experience. The same problem can occur in pepper, squash, cucumber, or melon fruits. Apple and pear trees also experience a very similar problem that is called “bitter pit”.

Figure 1. Blossom end-rot on tomatoes is a disorder caused by calcium deficiency.

So what is Blossom-End Rot?

It’s important to know it is not a disease. It’s a physiological disorder caused by calcium deficiency.

What causes Blossom-End Rot?

There are several culprits here to mention, but the most important ones are:

1) soil moisture fluctuations that are not within plant tolerance (soil that is too wet or too dry), and

2) applying too much nitrogen,

Applying too much water and/or applying fertilizers rich in nitrogen stimulate more foliage growth. Fruits and foliage then compete for calcium and fruits end up with not enough calcium and end rot happens.

Applying too little water also leads to plant water stress and negatively affects the ability of plant roots to absorb calcium from the soil.

How to get rid of end rot?

A balanced relationship of available water and calcium is essential to be able to predict and manage blossom-end rot.

Monitoring water status during the growing season using a soil moisture sensor can help maintain plants well-watered. This can decrease the occurrences of blossom-end rot and improve fruit size and quality.

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