posted 4 years ago
It depends on what type of fruit tree you are talking about. Apples will either produce flowers on young shoots from the previous season, or on established spurs that will persist for several years.
Pruning really has two functions: "Pruning for form" is how you shape the tree into a convenient configuration. For example, removing inward-growing branches to open the center of the tree and let it air and light, removing crossing branches to prevent one branch from shading another, or just removing vertical growth each season to restrict the overall height of the tree.
"Pruning for fruit" covers all the things that you can do to encourage (or discourage if the tree is still young) the formation of flowers and hence fruit. Apples, for example, will not set flowers on vertical shoots. So by retaining more horizontal shoots, you will encourage more flowers the next season. If you are growing spur-bearing types, you sometimes need to thin out the spurs so that there is enough space for the fruit to develop.
There are lots of good books that cover the basics of pruning a variety of different trees. Some trees require very little pruning, like Walnuts or Persimmons, but in general, pruning will get you more fruit, and be faster, AND yield higher quality fruit than just letting a tree "do its own thing." Modern fruit tree cultivars are no longer wild trees - they have been adapted to a certain amount of care. Some will even set so much fruit that they will break themselves apart if you are not diligent about dropping fruit or propping up branches.