Many citrus fruits including sweet oranges and especially mandarins (tangerines) have a strong tendency to alternate bear. Year after year, medium to heavy yields will alternate with a light yield. The reason for this is that it takes considerable energy to bring fruit to harvest. This is especially true for those varieties whose crops overlap, that is, the ‘old’ crop is still hanging on when the tree blooms once again. In essence, a tree must rest the year following high production. Again, there is just so much energy to go around. Alternate bearing isn’t always exact, but a season of heavy production will usually be followed by a year of low production.
To explain more specifically, because a tree carries such a heavy load of young developing fruit in the ON year, the number of summer and fall vegetative shoots that the tree produces will be reduced. These shoots carry flower buds for the following year’s production. Since the number of shoots is reduced, flower bud and thus fruit production will also be down, resulting in an OFF year.
Alternate bearing can be offset by reducing the fruit load on a heavy fruit set year. This is accomplished by thinning some of the fruit before the summer flush. This will also cause the remaining fruit to grow larger. Pruning the tree will give similar results. It is also recommended to pick the fruit as early as possible.
