Neglected apple trees offer less fruit, and the fruit they do bear is often poor in quality due to crowded branches and limited light in the canopy. Gardeners can revive an overgrown apple tree, but the process takes three years with two annual pruning periods. Do not attempt to prune an overgrown apple tree in one year. After all this hard work, gardeners will be rewarded with an increase in fruit production and better-tasting apples.
Locate any dead, diseased or damaged limbs on your overgrown apple tree in early spring, before the tree has begun growing for the season but after frost danger has passed. Dead limbs are hollow-feeling. Diseased limbs display physical blemishes and damaged limbs usually show cuts or bruises. These need to be removed immediately for the tree's health.
Prepare a 1:10 solution of bleach:water in a bucket. Dip your pruning tools in this. Cut away dead, diseased and damaged wood at the base. In between each cut, dip your pruning tools in the bucket to disinfect. Use anvil pruners for small limbs and lopping shears for those larger than 1-inch in diameter.
Cut away any interior limbs that compress other branches. This helps open up the canopy to produce air circulation. Remove these limbs by cutting them off at the base with lopping shears or with a pole saw if they're too thick to cut with lopping shears.
Trim down the height of your overgrown apple tree. Oregon State University suggests trimming a 20-foot apple tree by six to eight feet in the first year. Use a pole saw to cut back limbs and erect a ladder near your fruit tree to reach tall branches. Once you've reduced the height of your old tree, your first year pruning is complete.
Remove nearly all the vigorous new growth that is sprouting from the top of the tree over the summer. Leave only shoots that do not shade the lower limbs. Then wait until early spring to perform second year pruning.
Thin out shoots in the upper region of the tree during early spring of the second year. You can remove two more feet of overall height with your pole saw or leave the tree's height as-is.
Prune out old growth to space fruiting wood. Remove wood from crowded areas and weak growth that will not be able to hold a grown apple. Trim off any new shoots that grow upward rather that out. This completes second-year pruning.
Wait until summer then inspect growth at the top of the tree again. Clip off half of the developed shoots, leaving the slow-growing shoots and eliminating the vigorous ones. Then wait until the dormant period for third-year pruning.
Prune back the tree's long limbs by one to two feet, using your lopping shears. Cut back to a node or a swollen joint of the limb. At this point, your overgrown apple tree should be short, evenly spaced and significantly less dense than when you began. While your restoration program is over, continue to prune the apple tree every year during its dormant season.