Contact: Diane Relf, Extension Specialist, Environmental Horticulture
Posted November 1997
Quite frequently, peach and apple trees set more fruit than they can mature to a desirable size. By thinning or removing excess fruit this difficulty can be overcome. Thinning not only allows for an increase in size of the remaining fruit on the tree, but also improves fruit color and quality, reduces limb breakage, and promotes general tree vigor. Thinning helps maintain regular, annual bearing in certain apple varieties, such as Golden Delicious, Yellow Transparent, and York Imperial, that otherwise have a tendency to bear heavy crops every other year. Another benefit from thinning fruits is that it permits more thorough spraying or dusting for effective disease and insect control.
Experimental results indicate that the sooner peach trees are thinned after bloom, the earlier the ripening and the larger the fruits at harvest. It is doubtful that final size of the fruits of any variety will be greatly increased by thinning if it is delayed much after the pits begin to harden.
It is generally recommended that peaches be spaced 6 to 8 inches apart on a branch. When thinning by hand, grasp the stem or branch firmly between your thumb and forefinger and pull the fruit off with a quick motion of the second and third fingers.
Many growers use the pole method of thinning peaches. A 4- or 5-foot section of bamboo or other light wood is used. A piece of 3/4-inch garden or spray hose about 15 inches long is forced tightly onto the end of the pole, leaving 8 to 10 inches of the hose extending beyond the end of the pole. A snug fit is necessary so the hose will remain in place while being used. Many modifications of this tool are used. One of the most common is a 30-inch section of plastic pipe, 1 inch in diameter. Remove peaches by striking the limbs about 18 inches from their tips with the flexible part of the hose, using sharp, firm blows. This dislodges any loosely attached fruits. With a little practice, you should be able to remove individual fruits by this method.
Apples should be thinned as soon as possible after the fruit has set. If full benefits are to be obtained, thinning should be completed within 20 to 25 days after full bloom. In hand-thinning apples, use the same general technique used in hand-thinning peaches. A distance of 6 to 10 inches between fruits is recommended. With varieties of Delicious apples, where greater size of individual fruits is important, the greater spacing is preferred. The center apple of a cluster is usually the largest and the best apple to leave.
Thinning plums usually is limited to the large, Japanese varieties. The primary concern here is to facilitate insect and disease control. Plums are usually thinned by hand to about 4 inches apart.
(Originally published in The Virginia Gardener Handbook, Diane Relf, Editor, Environmental Horticulture, Virginia Tech, Blacksburg, VA 24061-0327)