There are several reasons to prune peach trees: to remove dead, diseased, or damaged branches; to develop and maintain an open-center structure; and to encourage new growth. Proper pruning will promote a good harvest of peaches. Peach trees should grow approximately 18 inches of new growth a year; providing adequate nutrients/fertilization is important to reach this goal.
Peach trees should be planted in a site that receives full sun. They will adapt to most soils, including sandy loams or clay loams, as long as they are well-drained. According to the University of Missouri, the ideal soil pH is 6 to 6.5. A site with high elevation is ideal as the cold air will drain away from the tree, which limits the risk of frost damage. Trees can be planted in spring---the bud union should be kept one inch above the ground. (Planting a peach tree deep in the soil can kill the tree.)
Open Vase Tree Form
Train peach trees to grow in an open vase tree form. The tree will not have a main leader, but instead it will have three or four branches or scaffold limbs coming out from around the trunk of the tree. Scaffold limbs will be approximately 26 to 30 inches above the ground level. The center of the tree should remain open---prune away any errant shoots that grow into the center of the tree in order to maintain the open vase tree form.
Pruning a Year-Old Peach Tree
Prune year-old peach trees in early spring before any growth begins. Prune to develop the open vase tree form. Remove one-third to one-half of the previous year's growth. Shorten any lateral branches that are growing from the scaffold limbs. Prune any shoots growing up through the open structure.
Pruning in the Next Five Years
Once you have established the open vase tree structure/form the branches that come off of the scaffold branches will need to be shortened each spring. Again, your aim is to keep the center of the tree open. Peaches are produced on year-old wood so new growth should be formed each year.
Pruning a Mature Tree
Keep mature peach trees at a manageable height---all branches taller than seven or eight feet should be trimmed. Trim out year-old fruiting wood (10 to 20 percent of the year-old wood). Remove any upright branches that are coming from the trunk and main scaffold branches.
Fertilize newly planted peach trees one month after planting, using 1/2 cup of a 12-12-12 fertilizer. Apply the fertilizer six inches from the trunk around the circumference of the tree. Fertilize a year-old tree with one to two pounds of the 12-12-12 fertilizer. Apply the fertilizer in early spring. Once the tree is bearing fruit, apply up to five pounds of the 12-12-12 fertilizer. The University of Missouri states, "The amount to use depends on the type of soil, the amount of pruning, the cropping load, and fertilization of the surrounding area (such as lawns)."