Growing Fruit Trees in Maine - Fruit Thinning
Allowing the tree to bear too much fruit can be stressful for the tree. Fruit thinning promotes good winter hardiness which is particularly beneficial for peach trees. Reducing the number of fruit on a tree will enable the remaining fruit to grow to a larger size and to ripen more quickly. Thinning also prevents limb breakage that occurs with a heavy load of fruit. To counteract over production of fruit, thinning in early summer is commonly done to remove the excess fruit. Apple, pear, peach and plum benefit from fruit thinning.
The optimum time for fruit thinning is late in spring or early in summer. The sooner thinning is completed, the more it benefits the tree. Fruit thinning is best done by hand when the fruit are half an inch to an inch in diameter.
The amount of fruit to remove depends on the number of fruit on the tree. Remove enough fruit so that there is no more than one fruit for every eight inches of shoot length on pears, apples and peach trees. On a plum tree, fruit can be spaced four inches apart. Pears and apples bear fruit in clusters. Removing fruit so that only one fruit per cluster remains is a common practice.
Chemical thinning is an option for large apple orchards which are too time consuming to thin by hand. Spraying carbaryl (Sevin™ insecticide) once or twice in the three weeks following bloom is an effective way to thin apple fruit. Two weeks after application, fruit will be shed so that hand thinning will not be necessary. It is important to read and follow the instructions on the product label for effective thinning and for safety precautions. Carbaryl does not work on peaches or plums and causes pears to become misshapen. For more instructions on spraying, see the section on spraying.