Peach trees should be pruned in the early spring just before bloom. Pruning in the fall and early winter should be avoided because the pruning wounds remain open and subject to disease invasion until spring growth can close the wounds. Studies of peach tree-decline syndrome show that pruning in November, December, and January greatly increases the premature death of peach trees.
Pruning too late in the year also has its hazards. Hot, dry weather places stress on trees that is made worse by pruning. One of the main reasons to prune peach trees is to cause the tree to produce new bearing growth. The growth produced after mid summer may not give rise to fruit buds that will produce fruit for the next year. There is, however, a reason to do some pruning in the summer. A healthy peach tree grows so much wood and foliage that the tree tends to shade the fruit so that little or no sunshine falls directly on the fruit. Pruning away some of the excess growth shading the fruit and done at the time the fruit is beginning its final swell will produce sweeter fruit.
Jim Showen, Smith County Master Gardener
Texas A&M AgriLife Extension Service