Tomato Blossom Rot, what to do, and how to prevent it

This has been the first year when I have had any issues with tomatoes. Since I started growing tomatoes 5 years ago, I have been fantastically fortunate, producing more than we can consume. The first issue we had was that my cages blew over from a tropical storm and broke off some of the flowering branches, not quite ready to pick. I then soon discovered horned worms while cutting off the broken branches eating away at the plant. Now that the tomatoes are starting to ripen, I have noticed that the bottoms are black.

At first, I thought that the horn worms had something to do with this, but I only found two of them and the problem did not go away. My first notion was to simply get rid of this year’s tomatoes and plant a fall crop in its place. But what lesson would I learn? Could this have been prevented? Plus, there are quite a few healthy-looking tomatoes on the vine that could be saved.

I took a photo of the black tomato bottom and presented it to one of the retail associates at Agway and my questions were tomato blossom rotanswered.

The associate explained to me that the cause of the tomato bottom rot is that the tomato plant is not getting enough calcium. Calcium is important because it helps build the tomato skin which protects the fruit from disease and bacteria. If the skin is not tough enough, then bacteria can penetrate the fruit which causes it to rot.

Tomato blossom rot can also be caused by a water deficiency in which the plant cannot take up calcium through its root system.

Applying Garden Lime

There are a few products out there that specifically target tomato blossom rot. The Agway that I stopped by was out of these products, but the retail associate stated that I could use plain garden lime which comes in a 40-pound bag. I did not need that much for my garden, but I plan on patching up dead spots on my lawn soon and I know that I am going to need lime. If you do not need a big heavy bag of lime, the store associate stated that “Bonide” makes a good product as well (it is concentrated).


To apply the lime to my tomato plants I scooped out about 3 big cups of lime and dumped it into a gallon of water, mixing it until it became a slurry. I took the same cup and fill it up with the slurry and poured about 3 full cups around the bottom of the tomato plants. I also picked off all the bad tomatoes. I then let this sit overnight.


Testing the Soil

Fortunately, the next day my three-way meter arrived that I had ordered on Amazon. I wanted to make sure that I was watering the right amount so that the tomato plant could absorb the calcium it needed.

This device is really simple to use. Stick the probes deep enough to where the root system of the plant is located and let it sit for about 10 minutes.

Make sure the switch is at “Moist”. My soil was dry, between 1 and 2 (I checked this in the evening which is why it could have been so dry).


After watering the meter read at 8, which is pretty good.

I then switched it over to “pH”. The meter read a little over 7, which is a little too alkaline, tomatoes like the soil acidic between 6.0 and 6.8. I think I will be OK though as the season is coming to an end. Hopefully, the soil will level out a bit for next year.

In the end, I am glad that I did not discard the tomato plants and used this as an opportunity to learn about tomato blossom rot. Before I plant tomatoes next year, I will test the soil pH level to see if I need to add lime. I will also keep a better eye throughout the season and add more if pH drops below 6.

As always, I would love to hear any comments or questions.

Thanks for reading … My Fantasy garden!

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