Some of our best work at Cliff's Trees are the pruning or trimming jobs that we do. Sometime that is our favorite type of work. Not only are we doing it while we work, but did you also know that we read about this kind of work as well. Reading is some of our favorite past time. Here is a great book that we are currently getting into and some of the Introduction. The title: The Pruning Handbook 
Author: Steve Bradley

"Perhaps the most mystifying element of gardening is the question of when, how (or indeed why) to prune plants. What is pruning? Put in its simplest form, it is a means of controlling plant growth, productivity and shape by cutting and training.

To the fruit grower, for whom this ancient art is standard practice, this form of plant manipulation is essential, as it ensures reliable cropping. In the case of ornamental plants, rose pruning and hedge trimming are the practices most frequently carried out and documented. However, for most trees and shrubs, pruning is performed as a remedial operation rather than a routine one. It is common for an ornamental plant to be pruned only when it begins to encroach on a neighbour or over a path.

Pruning can be the answer to making an unproductive tree fruitful, but do not expect miracles! Years of neglect cannot be rectified in one season. The unknowing pruner who cuts because he thinks he ought to (without knowing how or why) can finish up with a plant which bears no flowers or fruit at all as a result of over-severe pruning or because the pruning operations have been carried out at the wrong time of year.

Aesthetic pruning, for those gardeners who are obsessed by tidiness and formality, and where trees and shrubs conform like soldiers on a parade ground, is done for entirely different reasons. Trees are ruthlessly lopped to a standard height and shape, shrubs cut back to a predetermined size and shape with all being as close to identical as is possible. The difficulty with this being that no heed is paid to the different growth rates of the plants.?

It doesn't just talk about tree, but it also talks about how to trim everyday plants, shrubs and others. It's great for anyone that wants to learn a bit more on pruning.