Trees provide shade, cool the air and generate oxygen. In addition to sunlight, water and the right nutrients, proper tree trimming helps trees live longer. Using standard pruning techniques keeps them healthy and discourages insects and disease. Most property owners can easily trim smaller trees themselves. Equipment may be required to reach taller branches in older trees and is often available at local rental centers.
Trimming is a periodic pruning task to maintain the general shape of a tree, keep its crown open so that air and light can penetrate and remove dead, injured or infested branches. The purpose of trimming should be to maintain the health of the tree. Major pruning activities, including crown reduction, removal of sculptural branches, rejuvenation, pollarding and "topping," are major tree surgery, not trimming.
Trim suckers---shoots that come up from the base of the tree---as soon as they begin to grow. Check for and trim "water sprouts" that grow in vertical groups along branches to avoid crowding and sapping of nutrients from outer sections of branch. Trim back any branches that seem to be growing outside of the general spherical or pyramidal shape of the tree during its dormant season---winter---or before the tree buds out in very early spring. Trimming should never substitute for periodic pruning to thin and shape trees during dormant periods.
Cuts on branch ends should be made just past a node---the swollen areas along the length of a branch. Two new branches will grow from this growth plate. Remove storm-damaged branches by cutting just above the "collar" or gathered bark around the place where the branch meets the central "leader" or main stem of the tree. The collar will close over the cambium and inner bark, which carry food along the tree's leader and limbs. Diseased or damaged limbs greater than 3 to 4 inches in diameter should be cut once from above and then from below at the final position. Heavier limbs should start with a cut from below, a cut from the top farther out, then another cut from the top at the collar or node. Double and triple cuts relieve the weight of the branch and prevent further shredding or ripping of protective bark.
Trimming requires sharp instruments to make clean cuts. Hand pruners come in several styles and in right- and left-handed models. "Loppers", long-handled pruners, are helpful for trimming small interior branches or reaching above. Curved-bladed pruning saws are necessary to cut branches more than a few inches in diameter. Reach high branches with a pole pruner, which combines a saw and lopping cutter that can be operated by pulling a rope at the base of a pole that may be anywhere from a few feet to 20 feet long. Sharpen tools regularly and sterilize equipment between uses with bleach or alcohol solutions to avoid carrying mold or infection from tree to tree.
Never trim trees that are growing into utility lines; call your local utility company. They have the experience and equipment to do the job properly. Cut crowded branches back instead of "tipping" or shearing to shape; the result will be a thicket of branches that will strangle the inside of the tree's crown. Remove lower branches to only one-third of the tree's height to allow air to circulate vertically through the crown.