When fruit trees come from the nursery, they are usually shaped properly. Once they've grown for a year or two, though, many get the urge to start trimming. How you trim is determined by whether you want fruit, shade or an ornamental tree. Train or prune the tree to encourage them to yield fruit, repair storm and disease damage or encourage growth.
Keep crowns six to eight feet off the ground by removing shoots along the trunk below the first "scaffold" or main structural branches of the crown. Take these shoots, dead branches and branches that grow at severe angles from the tree any time because they weaken or clutter the crown and are unlikely to produce fruit.
Remove branches so that air and light can circulate. In late spring when the tree is young, designate scaffold branches and take branches that are too close or rub against scaffold branches on the interior of the crown. Cherry, peach, plum and others should grow in an "open vase" form; remove upright branches to open the crown. Others, like apples and pears, grow best with a central leader, a single upright branch from which others grow; the sides of these crowns are kept open and the crown becomes pyramidal. Always leave enough shade on the center leaders of young trees to shelter them against hot sun.
Pinch branches of seedlings with your fingers to encourage branching. Use loppers or a pole trimmer to "head" or cut back branches that grow beyond the crown, removing less than a third of the branch.
Always sacrifice secondary branches to maintain structural branches that define the shape of the tree. Dwarf trees seldom require heading if they are kept thinned properly.
Trim any tree to create a fruit bush by heading back branches several times, beginning in spring for several years until the shape is established. Remove all top growth one or two times a summer each year thereafter.
Thin crowding or weak branches and head energetic growers missed in the summer during the dormant period. Trim "stone" fruits (fruits with a single hard seed or "pit") like apricots and peaches in very late winter rather than fall or early winter when insects and diseases are more widespread.
Rejuvenate old trees by making thinning cuts and removing dead wood the first summer, then by heading back branches by no more than one-third their length each summer for three years.
Leave enough branches with leaves to support the root system; gradual heading allows your tree to develop new shoots along structural branches.
Seal large cuts with tree whitewash; black tar or "sealer" attracts insects and does not allow the wound to heal quickly.