In most parts of the country, fruit trees should be planted in early spring. Where winters are mild (USDA Hardiness Zone 7 and south), fall is the preferred planting time. This allows roots to become better established before the trees leaf out the following spring. Fall planting is a little risky, however where winters may cause damage.
Plant the trees the day you get them, if possible. If weather conditions delay planting, keep the roots moist until you can plant. Bare-root trees will be wrapped in moist peat or a similar material when you get them; leave this intact when you open the package and add water as needed. Water balled-and-burlap container trees as needed. Soak bare roots in a bucket of water for a few hours before planting, keeping them in water until planting. Dig planting holes a few inches deeper and 2 times wider than the roots spread. Be sure to match the hole size with the type of rootstock. Set trees on standard rootstocks (including genetic dwarf varieties) with the graft union a few inches below soil level to reduce root suckering. (If the tree is budded high--a foot or so off the ground--set it just a few inches deeper than it grew in the nursery.) Set trees on dwarfing rootstocks with the graft union several inches above the soil; if the union is buried, the variety could root and overcome the rootstock's dwarfing effect. Set interstem trees with the interstem half above and half below the soil.
In all three cases, set the trees a little bit higher than you ultimately want them. Mound the soil up slightly (3 to 4 inches high and 1 foot in diameter) around the trunk to help drainage and reduce problems with crown rot. Don't add fertilizer of any kind to the planting hole or drastically change the soil texture. Never add any materials that might burn the roots, such as chemical fertilizers, fresh manure, or moth balls. Compost can be mixed into the planting hole only if the soil if very poor, and don't add more than a few shovelfuls--it can change the soil texture and cause poor drainage.
Cut off, rather than bend, any broken roots and any extra-long roots. Spread out the roots in the hole and tamp the soil around them firmly. Air pockets around the roots can kill the trees. Surround the trunk of each tree with a 14-inch mouse and rabbit guard before filling the hole completely. Place the guard so that the bottom 2 inches will be below ground when the hole is filled with soil. Pour 2 gallons of water around each newly set tree to thoroughly soak the soil.
Prune spring-planted trees only if it was not done at the nursery. Wait until early spring to prune fall-planted trees if necessary. When pruning, cut the trees off at about 30 inches from the ground, just above a bud. This pruning helps adjust the tops to the root system, which was pruned in transplanting, and avoids stressing roots too much.
If the tree has branches, remove any that are less than 18 inches off the ground. If any strong branches above this height arise from the trunk at a wide angle and in desired positions, you can leave them, but cut them back by one-half. Cut all narrow-angled branches off, even if you're left with few or no side branches. Buds on the trunk will grow into side branches that you can train to better angles. Begin training trees in early summer.