When fruit trees set too much fruit in one year, the stress can reduce the size of the following year’s crop. The light fruit load then stimulates a very heavy load the following year, beginning a cycle of alternate-year bearing. Break this cycle by thinning the fruit during heavy-bearing years, especially in apples.
Because fruit trees initiate flower buds for the following season only four to six weeks after full bloom, try to thin fruit no later than 50 days after full bloom, and the earlier you thin it, the better. Thinning delayed until midsummer cannot influence next year’s crop, but it can improve the size, color, and shape of the current season’s fruit.
Pull excess fruit off by hand when it is 3/4 inch in diameter. You can follow up and thin again several weeks later, this time removing the smallest fruit to allow more energy to be channeled into the larger fruit.
Be careful not to injure the flowering spurs on apples and other fruit trees; leave the fruit stem attached to the spur or branch to prevent injury. Hold the stem between your thumb and forefinger and push the fruit off the stem with the remaining fingers.
Leave one fruit per cluster and space these several inches apart. Apples should be spaced 6 inches apart; peaches and nectarines thinned to 4 to 6 inches apart; apricots and plums to 2 to 3 inches apart. Cherries and pears do not need thinning.