Intentional and simple pruning during the first 5 to 10 years of most new planted landscape trees will guarantee improved strength and reduce risk of failure. One of the most obvious and overlooked pruning strategy is to keep the lower branches clear of being struck by vehicles or lawnmowers.
Branches may seem pliable and easily reactive but minor wounds will lead to decay and weakness even on the healthiest trees. The second most important pruning strategy is learning how and where to remove a branch from the main tree trunk.
Branches should be cleanly sawed from the main trunk without damaging the critical branch protection zone or trunk collar. But also as important is the branch must be removed enough so that the tree will form wound wood over the area where the branch was attached before removal. A flush cut is not the goal, on some trees the branch may show a slight swelling at the base, the cut should be made just outside of this bulge.
The growth habit of trees can vary depending upon its nature, for instance, the purpose of a hybrid landscape ornamental tree’s trained structure varies greatly from a native hardwood or understory tree. Pruning of ornamental, flowering or decorative trees and shrubs is based on the role it plays in the overall landscape design. These type plants may require high maintenance techniques like shearing, espalier or topiary. Shade and hardwood trees are generally grown best by maintaining a central leader form. By focusing upon a central leader to grown into a mature trunk, lateral branches should be kept at a much smaller diameter than the main trunk. A definite problem to avoid is a dual trunk or codominant stem situation in a mature tree which can lead to failure at the intersection.
Properly pruning trees does involve specific tools, techniques and knowledge. While most homeowners find caring for their trees very rewarding, some situations call for professional advice and certified arborists are always willing to share their talents and educate other tree stewards, so do not hesitate to call when you need a hand.
Tree Owner’s Manual (USDA Forest Service):