BLOSSOM-END ROT IN TOMATOES: How to Identify, Control & Prevent

Blossom-end rot is a condition that affects tomatoes, peppers, squash, melons, and eggplant. This is a fairly common problem in western Oregon.  A classic symptom of blossom-end rot is the development of a depressed water-soaked spot that appears on the blossom end of the fruit. This can occur on either green or ripening fruit.  The spot will enlarge, becoming sunken and turns a leathery brown or black color. The spot can encompass the lower half of the tomato in time. Many gardeners believe this problem is caused by a disease. However, it is not disease caused. Blossom-end rot is a physiological condition that can be caused by a number of different factors during plant growth that are easily remedied.


-A lack of calcium in the soil. Low soil calcium is common in western Oregon.

-Extreme fluctuations in soil moisture. Very wet to very dry.

-Rapid growth in early season followed by extended dry weather.

-Excessive rain/irrigation smothers the plants fine root hairs.

-Cultivating too close to the plant, damaging the root system.

-Excess soil salts.


-Lime the garden well before planting in spring to add the necessary calcium to the soil. A rate of 50lbs. per 500-1000 sq. ft. is desirable. Also, put 1-2 extra handfuls of lime in each planting hole to give each tomato a little extra calcium.

-Maintain uniform soil moisture by watering regularly, but not to excess. Perhaps 2, maybe 3 times per week depending on soil type.

-Avoid using high nitrogen fertilizer or large quantities of fresh manure that can promote too rapid or excessive growth.

-Don’t cultivate deeper than 1” within 1 foot of the plant.

-If soil has excess salts, provide more water to leach the salts from the soil.

Plants with fruit that develop blossom-end rot can be treated with a liquid calcium spray solution to stop further development of the condition. This is to be used only as a stop-gap measure to save your crop. The solution can be applied 2-3 times per week, directly to the plants foliage. Ferti-lome Yield Booster is product Burns Feed Store recommends for foliar treatment. It comes in a concentrate and a ready to use form.