Answer: Peaches bloom lavishly, producing 10 times as many flowers as they need to set a full crop. The abundance of blooms ensures that even if a frost kills 90 percent of the blossoms, you'll have plenty of peaches. If frosts don't reduce the crop, far too many fruits will set, which can result in all fruits being aborted. In those years, you'll have to "thin" the fruits by removing some while still small. Thinning enables the remaining fruits to grow bigger and sweeter, reduces split pits and prevents the tree's branches from breaking under the weight of an excessive crop.
Soon after natural fruit drop begins, gently shake the limbs to knock off loose fruits that will fall anyway. Then remove scrawny, misshapen or poorly developed fruits that flick off easily with your finger. Next, twist off all diseased or insect-damaged fruits, dropping them into a bucket for disposal. Look closely for the crescent-shaped egg-laying scars of the plum curculio, about 1/8 inch long.
Thin the remaining peaches to about 6 to 8 inches apart, letting the biggest fruits remain. Don't leave fruits any closer than 4 inches apart or they may touch when ripe. Fruit rots thrive in the humid niches created by too-close fruits and spread rapidly across fruits that touch.
Some years you'll need to thin heavily, removing up to 75 percent of the young fruits. In other years the trees will need only light thinning in spots. When you're done thinning, rake up and dispose of all the dropped and thinned fruits to help prevent pest problems.
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