Calcium deficiency



Blossom end rot or black spot is a symptom found in developing tomato fruit. Tomato plants easily move most nutrients around the plants, particularly nitrogen and potassium; calcium however, an essential element of tomato growing, is a different ball game. If tomatoes are not watered properly and get dry around the roots when in flower (critically between 16 and 21 days after pollination after the first sign of a tomato fruit has formed), the problem begins.

When the plant is left too dry it struggles to move calcium around to the fruit and will take it instead to the foliage first, leaving a lack of calcium within the fruit, hence the problem. In simplistic terms the plant is taking action to save itself and in so doing is prepared to abort the fruit.

Identifying Features
Developing fruit show a black area on the bottom of the fruit, beginning opposite the stalk. This area is often infected by other bacteria.

Treatment
None.

Prevention
Continue to water and liquid feed the plant regularly but also add a level teaspoon of Calcium Nitrate to a gallon of water and add about a pint to each plant once every 10 days or so.