People who own peach trees can't wait to pick large, sweet, juicy peaches from them. But besides being rewarding (and tasty), picking the fruit is also necessary for the tree's health. Removal of excess, blemished or damaged fruit relieves the limbs of unnecessary weight, which can potentially break or injure them. Thinning out fruit will also allow the tree to focus its resources on more productive things like yielding a better quality peach harvest. Common-sense management of fruit production is not only healthy for your peach tree, but ensures growth of large fruits with maximum flavor and texture.
Thin peach tree blossoms in very late March or April, when they're just about to open completely, depending upon your area. They'll look a little like a piece of popcorn. Tape a toilet brush to the end of a broom handle or long stick. Gently "sweep" clusters of blooms with the brush so that some of them fall off. Removing some of the blooms will reduce much of your work later on by preventing the production of some excess fruit.
Remove excess fruits in mid-May, when the peaches have grown to about the size of a quarter. They'll be closely clustered together--probably touching each other--which won't allow fruit enough room to grow properly because there are too many with no space between them. Bunches of heavy maturing peaches will also stress and probably crack or break tree limbs. Cut the stem with sharp shears immediately above the green fruit -- don't pull or twist it off. Look for misshapen, damaged or diseased fruits, and cut them off as well. Leave about 4-5 inches between remaining fruits.
Thin developing fruits again in mid- to late June. The maturing peaches should now be given about 6-8 inches of space between each to allow for adequate air circulation and plenty of room for proper continuing growth. Your job will be much easier this time because there won't be nearly as many ripening fruits to deal with as there were in May.
Pick a ripe peach by grasping the fruit firmly with the sides of your fingers, which are gentler than your fingertips. Pull the peace straight off of the stem. Expect to pick sweet, ripe peaches from late August through September.