Black Spots on Tomatoes - Knowledgebase Question

Cohasset, CA
Avatar for NRogers781
Question by NRogers781
December 26, 1997
All of my tomatoes this last summer had a mushy black area at the blossom end of the fruit. What causes this? What can I do to prevent it?

Answer from NGA
December 26, 1997
Sounds as though your tomatoes developed blossom-end rot. This is caused by a calcium deficiency which is aggravated by fluctuating soil moisture and high temperatures.

It would help to know your soil's pH (tomatoes grow best within the range of 6.8 to 7.2). When watering, make sure you apply enough to soak all the way down into the root zone, and water only every 7 to 10 days. Try not to fertilize, unless the leaves look yellowish, and mulch your plants to help maintain soil moisture (a 6" layer of straw is good).

The fruits are still edible after you cut off the black area. If you leave it on, it will infect the rest of the tomato and bacterial soft rot will take over the entire fruit.

Better luck next year!

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