Tom I found the answer to the question you asked in this post. Citrus growth occurs in several flushes during each year. The 1st growth occurs as straight vertical shoots. No side branches or flowering occur on these new shoots during this initial growth period . The growth will eventually stop and the tree will enter a rest period. Side branching and flowering develops on these vertical shoots during the next growth flush. These side branches fill out to produce a round canopy, and produce the blooms for the next crop. During the next flush following the blooming flush only straight vertical shoots are once again produced which push through the preceding canopy to reach upward and outward. These shoots once again following another rest period eventually produce side branches and flowers to form a new canopy which is above and beyond the preceding canopy layer. Of course the first to reach the branching and flowering phase are the first branches that the tree produced,(on grafted trees) which of course are the lower branches. Each year the flowering (thus the crop) will move up the tree as those branches enter the branching and flowering phase. Therefore, on young growing trees the lower portion of the tree will always have more fruit than the upper parts. The crop location on the tree gradually equals outs as the tree gets older and older and becomes fully mature. Thanks for the post, it helped us all out encluding myself. - Millet