December is an excellent time to prune that big, old apple tree in the yard. The best way to prune it, in terms of production, is to cut it down all together and start over with a young, dwarf tree. Apple wood is excellent for the fireplace. It has a high BTU to weight ratio, and gives off an excellent aroma. A few people smoke meat with apple wood.
However, if you can’t bring yourself to lower the ax on that apple tree, it is possible to prune it to increase the yield of quality apples.
Generally, an older tree will have a single trunk coming up from the ground which branches out into three to five scaffold limbs. The scaffold limbs head up to the sky and branch out everywhere, often crowding each other. Because the top of the tree ends up shading the lower branches most older trees are umbrella shaped. If the tree produces any good fruit it will be found on the upper layer of this umbrella where it has been exposed to lots of light and air.
The objective of pruning is to expose as much of the branches to light and air as possible while making it easier to care for and harvest the fruit.
The first step in this process is to decide between two basic shapes for your tree. The “open vase” is what was described earlier as having the umbrella shape. The other is the “central leader” where the tree has a strong, straight, dominate trunk that is the center of the tree. The largest branches come out on the lower part of the tree and they progress to smaller, younger branches to the top of the tree, giving it a Christmas tree shape.
There are a few advantages of the central leader tree. Since most of the branches are close to the ground, pruning and picking is easier and spraying is made more effective. As well, the fruit is exposed to a great amount of light and air. The problem with an older tree is that it could require several years of corrective pruning to change from an open vase to a central leader type tree. To do this, one must first choose which limb will become the central leader. The best way to do this is to choose the one closest to the center of the tree, even if it zigzags its way up. The other large scaffold limbs should be cut down gradually over the next three to five years. New limbs should be allowed to grow out from the central leader to fill in the space left from the removed scaffolds. Also, when a branch grows too large in the top of the tree, remove it and let a new one replace it.
Whatever the shape of the tree there are several general rules to follow as you prune. The first is to prune out all broken and dead limbs. The center of the tree should be free of small branches that will restrict air movement. Limbs that grow downward will produce small fruit, since nutrients flow upward. Limbs that grow straight up grow too vigorously to produce much fruit, so its best to have limbs growing horizontally or slightly upward to produce a good amount of large fruit. If a limb is too long consider removing it completely and letting a younger limb grow in its place. Cutting the terminal bud off of a branch causes the rest of the branch to grow more vigorously and produce less fruit. If you do have to cut a branch back, do so to another branch that grows out or down. Not cutting a branch allows it to remain soft and flexible and sometimes the weight of the fruit will pull an upward growing branch into a more horizontal position where it will produce more fruit the next season. In the top of the tree leave some small branches to shade the exposed larger limbs, protecting them from sunburn during the hot summer.