Prune a peach tree in late winter when the tree is dormant, according to SFGate. After fruiting, it is safe to trim the tree for size issues. Removing dead or diseased branches should be done as soon as the problem arises.
Pruning a peach tree in the late winter gives the tree healing time and sparks new growth for the upcoming season. Try to wait for mild weather, as cold weather can cause dieback and bark injuries. Pruning a peach tree can help keep nutrients from being wasted going to a diseased branch or too much foliage. Topping peach trees in the summer can make pruning easier in the winter.