Whether grown indoors or out, neem trees must have well-drained soil. They are relatively heavy feeders, responding to organic fertilizers such as fish emulsion, bone meal and kelp with lush new growth. If leaves begin to turn yellow, the tree has been given too much fertilizer or water. Although neem trees are evergreen, they often lose their leaves in very dry periods or after a hard frost. Neem trees will quickly revive with regular watering or the onset of warm summer days.
Few pests attack the neem tree and most problems with neem are directly related to over watering.
Several different types of fungal diseases can cause die-back, and slugs that thrive in soggy spaces will eat the bottom leaves of small trees. These compounds appear to increase antibody production. Only when this system appears to be unable to stop an infectious onslaught is the more massive immune system involved. This then creates an enhanced response to any future challenges by disease organisms. When neem oil was injected under the skin there was a significant increase in leukocytic cells and perioneal macrophages showed enhanced phagocytic activity and expression of MHC class II antigens.