Tree trimming, also called tree pruning, is a common form of tree maintenance that ensures the health and beauty of a tree. This procedure extends to several aspects of individual tree care.
One method is the removal of sucker growth from the trunk all the way to the crown. When nutrients move up the tree through the cambium layer just under the bark, they have a tendency to be sucked up by heavy sucker growth on the way up. This will cause a lush mid-tree but a thin discolored and dying crown. By slicking these limbs all the way up, the nutrients will feed the crown, keeping it healthy and nice-looking. When you notice a tree with an ugly crown chances are you'll see a lot of sucker growth mid-tree.
Another aspect of tree trimming is the removal of dead limbs. Proper collar cuts must be made on these limbs not too close to the main trunk to avoid cambium layer die-back. Probably more trees die from an improper trimming job than any other cause. Professionals know how to make these cuts; don't let one of the many butchers with a truck and a saw ruin or even kill your tree.
Over time a tree will have a tendency to do some self-pruning. There can be various reasons involved but suffice it to say that these branches should be removed before they come down on their own. You can have anything from twigs to large limbs that naturally die.
Be on guard against limbs that are just too long and heavy. Some of these older limbs, especially on oaks, can have an inside fungus which will cause the limb to break off close to the trunk. I assure you that you will never know that the limb has this problem; it looks perfectly healthy though it is a widow maker, as we call them in the business.
Lastly, let me just say that trees, especially in the front yard can make or break first appearances of your home. A properly trimmed tree, in most instances, will give your house a stately appearance and a well-pruned tree can usually go 3-5 years before another trimming is needed.