Old apple trees are an attractive asset to your property, but old trees tend to become overgrown and gnarled to the point where they may be unsightly and stop producing fruit. Old trees require different kinds of pruning than young trees do, simply for the fact that you can't shape the trees' growth as effectively since they are older and don't grow as quickly. Be aware that fully restoring an old apple tree to production can take as long as three years, but cosmetic pruning can make a difference immediately in your landscaping.
Clear away any brush, shrubs or trees that are crowding the overgrown apple tree. If they are significant, this requires an electric or gas chainsaw. Especially be sure to cut any trees that are shading the apple, as they prefer full sun.
Time it right. The best time to prune an overgrown apple tree is in March or April, after the cold winter's dormancy but before the tree begins to grow in the spring.
Thin out any shade the tree is creating for itself. Old, overgrown apple trees tend to twist in on themselves, with lots of crossing branches turning into something of a thicket. The tree actually can end up shading its own center so heavily no fruit is produced. Prune from the top of the tree's canopy down to maximize the sunlight and air to the tree's center.
Cut with sharp pruning tools. Dull blades will only crush the tree branches, injuring them more. They should be very sharp to give a clean cut. Use bigger tools if possible; it's better to make a few large cuts than many small cuts.
Trim about one-third of the overgrowth you eventually want to cut out. Prune off any dead, dying or diseased limbs, and move on to prune off one of each pair of limbs that cross, as well as any that hang down. Try to leave those with slight upward angles or main structural limbs.
Repeat the process of trimming the tree down by about a third of the overgrowth for the following two years. The apple tree didn't get that way in one year, and it's not healthy to fix it all in one year. Each year, thin out thick clumps of growth and remove whole limbs, not partial ones that will regrow.