The proceedure of thinning fruits has several principles behind it. You cull misshapen fruit while it is still small so the energy of the plant now goes to make the remaining fruit bigger and better. And you also reduce the amount of the crop, thus saving the energy of the tree to produce another good crop the following year. This practise has been done by orchardists since ancient history. You get better quality fruit, can increase size of the fruit (especially if you thin heavily) and balance the energy of the tree to give its utmost to the crop left to mature. Even on light bearing trees, there will be branches with very heavy loads of fruit which need to be thinged, and other branches which are only lightly bearing a crop. Thinning fruit from the interior of the tree also increases the color/blush of the remaining fruit. The sun gives a nice blush to the fruit on the outside of the tree canopy. Conversely, if you are in a hot sun area, yyou may want to partially shade the fruit to prevent sunburn on the fruit.
Some fruit trees do not need to be thinned. Cherries (both sweet and sour/tart/pie types) do not need thinning as they are small sized already and a profuse crop is what growers strive to obtain. Most other fruits, apricots, apriums, nectarines, peaches, plums, pluots, apples, pears, persimmons will benefit from some amount of thinning. The fruit will be larger if you thin heavily. If you do not want bigger sized fruit(depending on variety, some get larger than others) then just leave more fruit on the tree and thin less. an easyb rule of thumb is to thin your hand’s width for smaller fruits (apricots, plums) and a hand’s length for larger fruits, peaches, apples, pears, etc. Thinning fruit from the shady interior of the tree is recommended as it will not ripen and sweeten up as well as those fruits exposed to more sunlight on the outer edges of the tree canopy.
When the fruit crop begins to mature and the individual fruits become larger, you may want to ‘prop’ the branch with some kind of support to prevent breakage. It is very disheartening to grow a crop, then see it not mature due to the weight of fruits hanging on a broken branch, the branch broken from the excess weight. Sometimes, a major scaffold branch will separate from the trunk and leave a huge scar, deforming the tree and maybe you will have to remove it later since it’s structural integrity has been severely compromised.
With the cane berries and bush berries, little thinning is needed. Annual pruning of branches(crowded and old material) is usually enough to take care of any excessively producing wood. although supporting heavy branches loaded with fruit is still a good idea if it looks like it may break the branches due to the weight.
In any event, when you harvest the crop, the weight of the fruit is gone and the plant springs back to support itself once again.
Now is a great time to do this if you have not done it already. T
The next important thing to do is to make sure the plants are well watered until the harvest is over. Fruits are generally very full of water(that makes them juicy!), so any shortage of moisture will also lessen the juiciness of the fruits.