Types of wood:
Suckers are vigorous shoots that arise from the roots or the rootstock shank below the graft union.
Watersprouts are vigorous upright shoots inside the canopy, often originating near a pruning cut.
Spurs are short lateral shoots (approximate length of 4 to 6 inches) that are the primary site of flowers and fruit for most modern apple varieties.
Leader is the main vertical axis of the tree.
Scaffolds are major lateral branches.
Types of pruning cuts:
Heading cut is removing part of a branch, but not the entire branch.
Thinning cut is removing a branch to its point of origin.
Stubbing cut is a heading cut into 2-year-old or older wood.
Bench cut removes a vigorous upright branch back to a horizontal side branch. This should be avoided as it creates a proliferation of vigorous shoots just below the cut.
Dutch cut is removing a branch except leaving a short stub on the main leader. Often, a new branch will arise from this short stub to replace the branch that was removed. This is often the approach used to replace a damaged or broken limb.
Growth Response to Pruning
Trees respond differently to different pruning cuts. Heading cuts into 1-year-old growth will produce strong growth of several branches just below the cut. Further, when more wood is removed (a lower cut), the regrowth is more vigorous. Where a single branch grew before a heading cut, several strong branches will grow the following year. Usually this is not desirable. Thinning cuts, where the entire branch is removed, produce less regrowth and are preferred. Stubbing cuts into older wood usually produce less regrowth than a heading cut into older wood. Where large cuts are made in the canopy interior, particularly on old trees, significant regrowth occurs. This growth is usually as water sprouts. Making large cuts usually results in a “cut and grow” cycle that is hard to escape. This cut and grow cycle becomes even more problematic when excessive nitrogen fertilizer has been applied. Where heavy pruning is required, avoid applying fertilizer Nitrogen.
Sometimes it is difficult to know where to begin to prune fruit trees. Some cuts are more important to make than others. The following protocol is suggested for pruning. Pruning steps by order of priority are to (1) remove problems, (2) establish and maintain tree shape, (3) space wood to allow for adequate light penetration.
Problems to address include removing diseased, broken or damaged branches, branches that are crossing or rubbing, or form a narrow angle from the main scaffold. Old branches with long complex spurs should also be removed to make room for younger more productive branches.
Tree shape should be maintained through selective thinning cuts. Pay attention to branch orientation, remembering the “45-degree rule.” Branches that are too upright will remain vegetative, while pendant branches (below horizontal) are typically shaded and too weak to be very productive.
Branch density is the final objective. Frequently evaluate branch density during pruning. Periodically take a step or two back to see what the tree shape looks like. Are dense masses of limbs present? Can light penetrate into the tree interior? Could you conceivably throw a baseball cap through the tree without it hitting a branch? You should be able to see through the tree when leaves are not present. Don’t just look through the tree from side to side. Also, look upward through the canopy. You should be able to see through the canopy this way as well.