A few weeks ago, we had a column about using the proper tools for pruning and now it's time to get to the task.  January usually begins the annual round of dormant pruning, but before you make that first cut, it's important to know why you're doing it and how the plant is going to respond.  If done properly, pruning will actually improve the health and vigor of a plant, but if done improperly, you very well may get a plant that grows wildly in every direction without good form.  A worst case scenario is a plant that becomes susceptible to pests and diseases due to incorrect pruning cuts, eventually declining and dying.  So, with this in mind, remember that there are basically four reasons to prune.

Prune for Plant Health
This is probably the most important reason for pruning.  If you look closely at an unpruned tree or shrub, you will see a jumble of branches criss-crossing and rubbing against each other as well as weakened wood from lack of light.  In addition, poor air circulation due to the tangle of branches creates a perfect environment for many diseases.  Pruning away some of these branches lets light and air in, and removing crossing stems helps reduce wounds caused by all that rubbing against each other.  When branches have broken due to high winds, heavy snow or other natural phenomena, they usually don't break off cleanly, so it's important to use a sharp saw or pruners to cut off the ragged edges.  Also, any diseased branches or those attacked by insects should be pruned off and discarded (don't put these in your compost heap).  When a tree is young, you can encourage its long-term health by pruning to direct growth so that limbs are anchored properly to the trunk; this will keep branches from breaking in high winds or even under their own weight.

Prune to Limit Growth
Proper pruning can keep a plant from growing out of bounds, but rather than having to do this every year, make sure you choose the right plant for the right location.  Everyone has seen entrances to homes completely dwarfed by too-large shrubs or windows that don't let enough sunlight in because of giant plants; the owners would do better by choosing the right plant for the location rather than hacking away at those shrubs every year – many times, pruning only promotes more vigorous growth.  In the case of fruit trees, rather than severe pruning, size can be controlled by grafting a stem onto a dwarf rootstock (apple trees are a good example of this technique).

Prune to Make Beautiful Plant Forms
Topiary and bonsai are two examples of pruning techniques done to achieve certain plant forms.  However, more frequent pruning is required for these forms and you must remember that no matter how much or how often you prune, a plant will always attempt to resume its natural growth habits, especially as it grows older. 

Prune for Better Quality of Fruits & Flowers
By removing branches from a shrub or tree, you can remove buds that might become shoots, putting more energy into those that remain.  In many fruit trees, fewer flower buds means fewer fruits, but those that are left get more energy from the plant.  The result?  The fruit you do get will be larger in size and sweeter in taste.  Some ornamentals produce show-quality blooms when you prune off all but a few flower buds, and some ornamental plants like chrysanthemums will be bushier and less leggy if you routinely pinch off some flower buds early in the growing season.

One more important thing to remember when you do your annual pruning:  Don't leave the debris on the ground!  This will just promote increased pest infestation and disease as there may be insect eggs or fungal spores overwintering in all that mess on the ground.  Discard the debris by raking up and either bagging it for green waste disposal or burning it with a proper permit.  Do not add the debris to your compost heap.