Calcium deficiency in plants: how to identify and correct it

Lack of calcium can especially affect young tissues and developing fruits. In tomatoes and peppers, one of the best-known symptoms is the appearance of a dark spot at the end of the fruit, on the side opposite the stem. This problem is known as blossom end rot. The spot may start small and progressively increase in size until the affected area becomes dry, dark and sunken. 

The main symptoms are: 

• Brown, dark or black spot at the blossom end of tomatoes and peppers. 

• Lesion appearing on the part of the fruit opposite the stem. 

• Spot that progressively increases in size. 

• Affected area that becomes sunken and develops a dry, leathery appearance. 

• Fruits with a dark and deteriorated area on the bottom. 

• Deformities or deterioration of young tissues in other plants. 

• Young shoots showing weak or deformed growth. 

Do not confuse with water stress. 

Lack or excess of water can contribute to the appearance of blossom end rot because it makes it difficult for calcium to reach the fruit correctly. However, the most characteristic symptom remains the dark and dry lesion at the blossom end of the fruit. 

Do not confuse with salinity or excess fertilizer. 

Burns caused by salinity or excess fertilizer mainly appear on the tips and edges of leaves, which can turn yellow, become brown and eventually dry out. Blossom end rot, on the other hand, mainly appears at the end of the fruit. 

Do not confuse with rots caused by fungi or bacteria. 

Rots caused by fungi or bacteria can appear on different parts of the fruit and usually produce soft, wet tissues that deteriorate quickly. In blossom end rot, the lesion normally begins as a dry, dark and sunken area at the end of the fruit.