What is a general sign of nitrogen deficiency in trees?

The sign of nitrogen deficiency in trees is characterized by yellowing of leaves, which is commonly referred to as chlorosis. Nitrogen is a vital nutrient required for the synthesis of chlorophyll, the green pigment in plants that is essential for photosynthesis. When a tree lacks sufficient nitrogen, it is unable to produce adequate chlorophyll, leading to younger leaves showing yellowing while the veins may remain green. This condition usually starts with the older leaves, as nitrogen is mobile within the plant and will be redistributed to younger growth if the tree is deficient.

Although stunted growth and leaf curling can also be signs of various nutrient deficiencies or other problems, they do not specifically indicate nitrogen deficiency. Root rot, on the other hand, is typically associated with overwatering or fungal infections rather than nutrient deficiencies.