In Maine it happens in early July. Therefore the decision to thin has to be made several weeks before one can really know how much thinning is needed. An educated guess is made based on the number of flowers, the weather and temperature during bloom and how active the bees were. If the educated guess wasn't quite right or if weather conditions weren't conducive to effective thinning, growers may hand thin in July when the apples are about an inch in diameter. Thinning also promotes return bloom.
Many apple varieties have a tendency to produce an apple crop only every other year.
Thinning counteracts this tendency. Pest control starts in the spring and continues throughout the summer. It will be discussed at some length in a later section . During July and early August the orchard is mowed at least once, usually twice. It is a job like housecleaning, never ending and as soon as everything has been mowed once it is time to start over again.