Baby peaches before thinning are too close together, which will result is smaller fruits with less sweetness.
Baby peaches after thinning allows room for the remaining fruits to become bigger and sweeter.
My fruit and nut trees — peaches, pears, apples and almonds — are looking like they will be absolutely loaded with fruit this year! We did not experience a late cold snap, which can kill the blossoms, and the bees did a great job with pollination. This is great news, but it meant a bit more work to ensure quality, large-sized fruit rather than getting lots of inferior small-sized fruit.
Thinning the fruit is the best way to get larger-sized fruits. There are also a number of other reasons for thinning fruit. The following are a few points to consider:
Fruit Size: If you thin, you can get good-sized fruit. If you don't, you'll get undersized fruit. Perhaps you will have a greater number of fruit if you fail to thin, but you will probably not like the ratio of pulp to pit. Here's a handy two-part rule: When it comes to larger fruits such as peaches or apples, if you can touch two fruits with one hand, you are allowing your tree to bear too much fruit. By following this rule, the plant will produce the largest fruit possible up to its genetic potential.
Sweetness: The tree is best able to develop the necessary sugars and therefore sweetness, by putting its energy into a smaller number of fruit. Although you will get fewer individual fruits per tree, they will be of much higher quality.
To avoid limb breakage: Limbs overloaded with fruit often break and fall onto the ground. They do so in a random and uncontrolled way that usually tears bark, thus exposing the tree to disease and insect attacks. If the limb can't bear the weight of the fruit, thin the fruit. Don't prop up the limb, which hurts the tree in the long run.
To avoid disease: If wind and air can't go through the tree and circulate between the fruit you have an increased potential for disease.
To reduce a tendency toward alternate bearing: A tree puts a lot of energy into producing and ripening fruit. Heavy fruit set demands a heavy expenditure of energy, and the tree will need to recuperate from this. For instance, a pear tree left unthinned during a heavy-bearing year might produce a big number of small-to-medium-sized fruit, then next year, none at all. By thinning out the very heavy fruit sets, you can avoid this problem. An exception is that some varieties are genetically programmed to be alternate bearing.
To avoid weakening younger trees: Allowing a very young tree to produce fruit retards its growth. It is better to remove all the fruit for the first couple of years to allow the tree to put its energy into becoming established.
To control fruit drop: Fruit trees tend to drop fruit spontaneously. If the fruit set is not thinned, they might drop all, or at least most of their fruit. This happens to my almond tree if I don't thin the nuts soon enough.
To stagger the fruit-ripening process: If you look at fruit set on most trees, you will see little green nubbins of varying sizes, indicating differing stages of development. If you thin fruit so that some remain in each of the various stages of development, you will be able to spread ripening over a much longer period. That is, the more developed fruits remaining will ripen first, the others, later. Or, you can select all fruits of the same stage of development so that they will all ripen at nearly the same time, which is good if you are canning or freezing them for use throughout the year.
To improve the appearance of the fruit: Some fruit should be thinned on the outside of the tree, which applies to fruit that is easily sun scalded such as persimmons or loquats. Other types of fruit, such as peaches and some varieties of apples, should be thinned on the inside of the tree because they need exposure to sunlight to color up.
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