The fruit of a citrus tree draws all of its energy from only the 3 or 4 closest leaves.The rest of the leaves puts their energy into the growth of the tree. If your trees has a lot of small fruits they can use much of the trees energy, witch will slow the growth of the tree. However, even on very small young citrus trees, Purdue University's literature states that leaving one fruit will not retard any of the tree's growth. Therefore, even on your smallest trees you can safely keep one fruit, and still obtain all of the tree's expected growth. - Millet (404-)