University of Hawaii at Manoa
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Tomato – Blossom End Rot

Blossom end rot from calcium deficiency. Photo: Dr. Scot Nelson

Blossom end rot on tomato caused by calcium deficiency
Photo: Dr. Scot C. Nelson, CTAHR


The blossom end of the fruit (where the fruit attaches to the stem) is discolored and appears to be water-soaked. As the disease progresses, the discoloration grows larger and turns brown or black.


Blossom end rot is caused by calcium deficiency induced by uneven watering.



Blossom end rot is a physiological disorder rather than a disease. To prevent it from occurring, you must control the amount of water your tomatoes receive. Water the plants regularly in dry weather and protect from too much rain. Mulching the plants can help, as well as growing tomatoes under cover or in a greenhouse in rainy areas. You may want to add calcium or lime to the soil before planting.

Kendal Lyon, Hawaii Island Master Gardeners