Thinning Fruit on Apple Trees

Each year, beginning in July, an apple tree will begin to pruduce flower buds for the following year.  This buds, of course, remain dormant during the winter, but the following Spring begin to open, as temperatures warm.  Each bud will produce five flowers, and if properly pollinated, will produce 5 apples.  The number of potential fruit is in the 10's of 1000's.  Most of these, of course, will not make it to the fall season, as the tree will naturally shed most of them, even if properly pollinated.

 

However, despite that, if the fruit are not thinned even more, the fall crop will be small apples of low quality.  Also, since so much energy is going into the current year's fruit, very few flower buds are produced for the next year.  That is why apple trees tend to bear every other year. 

 

To ensure a crop of high quality fruit each year, the fruit must be thinned each Spring.  As a general rule of thumb, the number of fruit on a tree can be deteermined by measuring the diameter of the trunk.  Square this number, and multiply by 40.  For example, a 3" diameter tree should have 3 x 3 x 40, or 360 fruit.  Therefore, fruit in excess of that number should be removed, when the diameter is about 5 millimeters, or about 1/4 inch.

 

This thinning can be done by hand, or can be done by spaying thinning chemicals.  The most common is Sevin.  Sevin is known to stress these young fruitletts, and the weaker ones drop off.  Of course, there is the danger of thinning too much, or not enough.  Much experience will is necesary to do it properly.