Proper tree trimming techniques are dependent on good timing. Never trim in April, May or June. Trimming in the spring will put stress on the tree and deplete it of energy required to form new leaves. Never trim November through January because there will be insufficient time to heal open cuts, leaving the tree vulnerable to the cold. Trim only in the dormant season, preferably in the dead of winter. February and March are best, but mid- to late summer is also acceptable depending on the climate. Flowering trees are the exception and should always be trimmed within three weeks following the end of the blooming period.
Remove dead branches whenever possible. This will not only improve the appearance of the tree, but will benefit overall health by preventing fungal growth. Freeing the tree of dead branches is a simple technique requiring a single cut just above the collar at the base of the branch to allow the bark to close around the wound and heal. Always cut from underneath to prevent the weight of the branch from ripping the collar.
Crown reduction should only be performed when trees are located near power lines or other physical structures that may be impeded by the tree's growth. This usually results in height reduction and branch spread. This technique should only be performed under extreme conditions since some cuts may result in open gaps leaving the tree vulnerable to the effects of bad weather.
Thinning the crown involves strategic cutting of the upper branches to allow better air flow and expose lower branches to much needed sun. This technique is also required to relieve stress from the weight of heavier limbs resting on top of weaker ones.
This trimming technique is applied when lower branches impede movement below the tree. Lower branches are uniformly removed to a predetermined height to allow free movement. Raising branches may also be indicated to fulfill a municipal requirement.