Blossom End Rot

Posted by Sunset Garden Experts on

blossom end rot

Blossom End Rot

What is it?

Blossom end rot is a problem most commonly associated with tomato plants, though it can also affect peppers, eggplant, squash and melons.  This problem can be attributed to low levels of calcium in the soil or an inability for the plant to draw the calcium from the soil due to water shortages, poor uptake of calcium through the stem, or excessive usage of potassium or nitrogen based fertilizers.

This problem will be more common with the first few fruits if you planted in cold soil.  It’s also common when the soil in your garden experiences extremes in soil moisture (too dry or too wet). 


On tomatoes and peppers blossom end rot starts at the blossom end of the fruit, furthest away from the stem.  The affected area will become discoloured and sunken.  It will start off small and grow larger and darker as the fruit continues to grow.

blossom end rot in tomatoes and peppers



There is no defined cycle for blossom end rot.  You should examine each fruit for signs of rot.  If you are experiencing the same problem year after year you should test your soil to check the calcium level.  If you don’t generally have this problem, review your watering practices.

What causes it?

Blossom end rot is caused by calcium deficiency.  This may be the result of low calcium levels in the soil but more often than not it is the result of erratic watering practices.  If a plant is allowed to get too dry or given too much water over a period of time its ability to absorb calcium from the soil is reduced.

How to treat it

If your soil is low in calcium, the easiest way to treat it is to add lime to your soil several times a year based on the results of your soil test.

If the problem is a moisture issue here are some suggestions:

1. Pay closer attention to watering - Try to keep a consistent soil moisture level, making sure that your soil isn’t allowed to dry out.

2. Mulch – Adding a 3 inch layer of mulch on top of your soil will help maintain adequate moisture levels in your soil even during dry spells.  This is best done after your soil has warmed up in the spring.

3. Plant crops that are susceptible to blossom end rot (such as tomatoes, peppers, eggplant, squash and melons) in well draining, deep soil that has been amended with lots of organic matter.  This will better retain moisture in your soil and supply plenty of nutrition (including calcium) to your plants.

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