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Blossom End Rot on Tomatoes

By February 24, 2016 July 24th, 2020 Pests & Troubleshooting

Blossom End Rot on Tomatoes 

Blossom end rot is a common issue with tomatoes and it can seem dire when you see it in your own garden. But don’t panic! There are a few great ways to prevent blossom end rot and to curb it if you do see it on your first tomatoes of the season.


What is blossom end rot and what causes it?

Blossom End Rot is a physiological disorder in tomato plants that causes the blossom end of the tomato fruit (the bottom of the tomato away from the stem, where the blossom falls off) to become leathery, black or brown in color, and rotten. It has long been said that blossom end rot comes from a calcium deficiency in the tomato plants.

Research shows that although blossom end rot is indeed a calcium issue, it typically results from inconsistent watering or having plants that are over-watered or under-watered.

The inconsistency in watering stresses the plants, making them more susceptible to things like end rot. Also, a lack of or an excess of water can make calcium in the soil unavailable to the plant, thus resulting in a Ca deficiency (which is key for tomato health). Blossom End Rot is particularly common in CO after exceptionally wet springs that are followed by very dry periods when the plants are beginning to produce fruit.

Blossom end rot is not a disease that will spread among tomato plants, so there is no need to pull out plants or fear that it will spread on its own.


How do I prevent blossom end rot?

  • In the first 2-3 weeks after your tomatoes have been transplanted, encourage deep and wide root growth by watering deeply and then letting the soil dry out a little more than usual between watering (without letting the soil dry up completely). This will set your tomatoes up for success by encouraging them to develop a lot of feeder roots and deep tap roots to find all the necessary nutrients.
  • Consider mulching your tomatoes to keep your soil hydration more consistent.
  • Tomatoes are one of the most over-watered garden vegetables! So more than likely your issue is OVERWATERING.


I did all that (or not) and I still have blossom end rot! So now what should I do about it?

  • Don’t panic! It is very common to get blossom end rot on your first tomato fruit set, but tomato plants will typically self-correct after their first fruits, so typically you’ll see beautiful healthy fruit come next. Just be patient.
  • Monitor your soil moisture and make sure that your tomatoes are getting adequate water, but not too much. Refer to our Irrigation 101 blog post to get an idea about how often to water and how to tell if your soil is moist enough.
  • Pull of the affected tomato fruits off the plant and compost them. Check your irrigation to make sure you are not over or under watering significantly. Get a good soluble (liquid) Calcium amendment or a general tomato fertilizer with Calcium in it from any nursery or online and apply to your plants, according to the product specifications.


If minor, many gardeners simply cut the black affected area of the tomato off, leaving the remaining 80% of the tomato delicious and ready to eat!


About bryantm251


  • Robin says:

    Awesome advice! Not giving up… Going to try this this year.

  • Who gives you good pure oxygen, shade, fruits and flowers? Plants are just great. I like reading the blogs on growing and benefits of plants. Even watching images of the plants gives a sense of peace to our mind. Keep posting more.

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