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Lots of red tomatoes

Blossom End Rot on Tomatoes

What’s with the name?

A common issue, when growing your own tomatoes in Florida, is blossom end rot (BER). With Blossom end rot, tomatoes begin to rot while still on the plant, opposite of where the stem is connected to the fruit, and where the blossom was once attached. This is where blossom end rot develops. This end of the tomato, at some point in its development, starts to become discolored and finally rots. Unfortunately, blossom end rot often happens to your tomato within weeks or even days of the harvest. Peppers, squash, cucumbers, and melons can also suffer from BER.

A Green Tomatoe shows early signs of Blossom End Rot

A green tomato shows early signs of Blossom End Rot. Discoloration may appear on the sides of the fruits. Photo from UF Plant Pathology Dept.

Why are they rotting?

The culprit is a calcium deficiency. Because the fruit is deficient in calcium, it weakens the cells within the fruit, which is followed by secondary fungus or bacterial rot. Too little available calcium in the soil, over-fertilization with nitrogen and not keeping the plant evenly watered are common reasons for this condition.

Is there a solution?                  

First, you want to make sure your plant has plenty of available calcium. This needs to happen throughout the growth of the plant not when you see a problem. Once the problem has manifested itself, fixing this condition with soil or even foliar calcium applications is generally not effective. There are some products for homeowners that contain liquid forms of calcium that can be sprayed regularly on your plants.  The condition is easier to prevent than to cure.  If your problem comes in April you won’t be able to correct it before the tomato season ends in the middle of May. By then, night temperatures above 70 degrees hamper pollination, warm daytime temperatures cause excessive growth, and insects and disease become unmanageable.

Watering plays a crucial role

It’s important that watering is kept at an even level. Alternating wet and dry irrigation applications and letting plants dry out by the evening make them very susceptible to BER. Overfertilization can cause excessive growth and redirection of water resources to the leaves and away from the fruit. When water doesn’t make it to the fruit, the calcium it carries also fails to make it there. Paying attention to these cultural practices should help you avoid BER.

Advance stage of BER on an almost ripe tomato

Advanced stages of blossom end rot. Fungal and bacteria rot become prevalent. Photo from UF Plant Pathology Dept.

Learning Florida’s Lessons

Learn more about growing vegetables in Florida at my online fall vegetable gardening workshop on August 15th .  You’ll be able to pick up a 100-page starting on August 10th at the Extension office.  Learn more on Eventbrite or for more information call the UF/IFAS Extension office of Highlands County at 863 402-6540 or email me at That’s the news from the Hometown Gardener. You can find and “Like” my page on Facebook at Hometown Gardener.

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4 Comments on “Blossom End Rot on Tomatoes

  1. We haven’t planted a large garden in years, and this year’s garden is a newly-tilled area of the yard not previously used. We now have blossom end rot in our tomatoes. We are applying Rot Stop but I don’t know if we will be able to save our crop. Is is too late to replant, will any treatment to increase the calcium content of the soil work in time, or are we done until next year?

    Thank you?

    • Hello Henry. It is too late, in my estimation, to start tomatoes in Florida now. I would start them mid-August and they should be ready to fruit by October when the night temperatures are below 70 and cool enough for successful Pollination. Blossom End rot is really hard to reverse and pretty much impossible by this time of year. The tomato fruit that are just starting might be saved but I don’t think it is worth your time. Thank you for reading my blogs. I hope you will follow me on Facebook too
      at Hometown Gardener.

  2. Hi Henry,
    After reading your article about BER I know it is too late in the season to stop it. What product do you recommend for next year’s crop?

    • Keeping your plants evenly watered (not letting them dry out between waterings)is important as well as not over fertilizing them. Check the pH is proper (5.5-6.8) some people claim to put a tums in the ground next to them when planted. If the cultural practices are not right it may not matter how much fertilizer you use.

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