As with other fruit trees, the main goal of pruning apple trees is to increase fruit quantity and quality. On young trees, training and pruning establish a healthy framework of branches. Continue pruning once or twice a year to maintain the structure.
When to prune. The most important time to prune is late winter before you see any signs of new growth. Prune off damaged limbs as well as branches that grow too close to the main branches. Thin out crowded and crossing twigs. Choose limbs to form another layer of main structural branches above the previous layers, and remove competing branches. Trim back by two-thirds the new growth at branch ends and from the central trunk (leader).
In midsummer, remove all new shoots that grow straight up or down from the limbs and from the base of the tree. If the main trunk is forked, remove the weaker shoot.
Where to cut. Don't randomly shorten branches; remove them all the way to their bases. Start by locating the branch bark ridge, a raised area on the upper surface where the branch meets the trunk or larger branch. Begin your cut just outside this ridge, angling it down to the outside of the branch collar, the bulge that forms at the base of the branch where it intersects with the trunk. Leaving the branch collar intact will help the cut close over more readily. Don't cut branches flush to the trunk, and don't leave stubs.
To avoid tearing the bark as you cut through a branch that is too heavy to hold up yourself, divide the cut into three steps. Cut first from the bottom, 6 to 8 inches out from the location of the final cut and half way into the branch. Make the second cut from the top, about an inch further out than the first cut. The branch will break off once this second top cut reaches the area of the first bottom cut, and a stub will remain. Remove the stub in one cut just outside the branch collar.
Prune twigs back to within 1/4 inch of a bud that points in the desired direction, usually toward the outside of the tree.
Training young trees. On 2- to 3-year-old trees, remove all branches within 30 to 36 inches of the ground and large branches that grow parallel with the main trunk (central leader) at the top of the tree. Choose three or four well-placed branches spaced evenly around the trunk and 6 to 10 inches apart vertically. Branches should form a wide angle with the trunk (not narrower than 45 degrees). These become your permanent scaffold branches. Prune off the other branches. Do this in late winter while the tree is dormant. In subsequent years, add one or two more layers of scaffold branches, spaced 12 to 15 inches apart.
Spread the branches. Branches that form a 45 degree to 60 degree angle with the trunk produce more fruit and are less likely to break under stress than ones at narrower angles. To widen the angle of otherwise desirable branches, wedge a notched stick between the branch and trunk to spread them apart. Install the spreaders in late winter and remove in late summer.
Use pruners for cutting limbs up to 3/4 inch diameter. Loppers can handle up to 1-1/2 inch cuts. Use a pruning saw to remove larger branches.
When apple trees reach a desirable height, cut the central leader back to the uppermost branch and remove subsequent upward-growing shoots.
Photography by National Gardening Association.