Ready to prune? Do it carefully: There's only one right way
Although pruning can't help but wound a plant, that wound needn't compromise the plant's health.
Plants have an uncanny ability to deal with wounds, the cells around the cut multiplying to seal it off and releasing natural chemicals to fight infection. Your job, as a pruner, is to pinch, snip, lop or saw in a way that will promote your plants' natural healing.
First and most important: Make all pruning cuts clean. Ragged edges leave more damaged cells and more surface area to close over. Sharp tools are a must.
Smaller cuts leave smaller wounds, so prune off that misplaced maple limb when you can do it with hand shears, rather than when you need a chain saw. Removing small branches is also less debilitating to a plant.
Pruning off diseased stems can be a way to thwart certain diseases, but watch out that you don't inadvertently spread infection in the process. When disease transmission is a hazard — with fire-blight disease of pears, for example — sterilize your pruning tool between cuts by dipping it in alcohol.
Pay attention to where you cut stems. Any length of stem left above a bud becomes a dead stub; and you'll get a dried, dead bud from cutting too close to it. You can avoid this if you cut just a little beyond a bud when you shorten a stem. Cut at an angle, with the cut sloping down slightly behind the bud.
Removing a large limb with a single pruning cut pulls a long shred of bark from a tree as the limb comes toppling down. Instead, first undercut the limb one-quarter of the way through about 12 inches farther out than your eventual cut. Then saw through from the top, near the first cut but a couple of inches farther out on the limb. After the limb falls, saw off the foot-long stub that remains, cutting back to just beyond the ring of bark at the base of the limb.
After you have cut off a branch or limb, do nothing to that bare wound staring you in the face. Perhaps it's an innate desire for nurturing that has induced humans for centuries to cover wounds with dressings ranging from clay to manure to tar. Such dressings, for the most part, keep the wound moist — but maintain a hospitable environment for disease-causing microorganisms.
A good pruning cut, not a poultice, lets any plant seal off the wound and prevent any spread of infection. Take care how you cut, and appreciate a plant's natural ability to heal itself.