Chlorosis

Chlorosis is the loss of green color in leaves caused by a decrease in chlorophyll. It is most often a symptom of nutrient deficiency—especially magnesium, iron, or nitrogen—but it can also result from root damage or abnormal soil pH. The yellowing of leaves itself is not a disease, but a sign that the plant has a problem with nutrition or functioning. Before applying fertilizers, it is important to determine the actual cause of the chlorosis.