Trees growing near power lines can cause power outages during storms or when the wind is high. High voltage lines aren't usually insulated, and fires can start when branches rub on the lines and cause short circuits. In addition, hundreds of people are injured or die every year when they climb trees or prune trees near power lines.
Homeowners should never prune trees located near power lines. Only tree trimmers with Electrical Hazard Awareness Training are qualified to do this work. According to the University of Florida Extension, no one without the proper training should prune within 10 feet of a utility conductor. Sometimes property owners don't like the way utility contractors prune their trees, because it doesn't always look attractive. The purpose of pruning for line clearance is to direct tree growth away from the wires, not to give the tree an attractive shape. Contractors doing this work follow American National Standards Institute standards for utility pruning.
The International Society of Arboriculture says trees that reach a height of 40 feet when fully grown should be planted at least 15 feet away from power lines. Taller trees should be planted 40 feet away. Only trees that grow to 20 feet or less should be planted near power lines. Some towns allow residents to plant trees that can be trained to grow over the wires. Those towns don't have heavy ice or snowstorms. Check with your local town or city hall, and your local utility company, to see if this practice is allowed in your area.
According to North Dakota State University Extension, the following trees all grow less than 20 feet high and should be compatible with planting near power lines: Amur maple, common smoketree, Siberian peashrub, grey dogwood, redoiser dogwood, forsythia, foster holly, freedom honeysuckle, mugo pine, lilacs and viburnum. Selecting the proper tree for planting will reduce the need for pruning later on.
Horticulturists at North Dakota State University say the following trees should never be planted near power lines: ash, birch, black walnut, elm, honeylocust, linden, maples, oak, pine, poplar and willow. If grown near power lines, these trees will need to have their tops removed, making them susceptible to attack by insects or disease. Directional pruning will also destroy their attractive shape.
Homeowners may wonder about whether it's acceptable to plant trees near other types of lines like telephone or cable TV lines. The voltage from telephone and cable TV lines is lower and those lines are usually insulated, so they don't pose the same risk as power lines. Service interruptions can still happen if branches bring down wires, so homeowners should take the same care with those lines as they do with power lines. In addition, the roots of trees that are planted close to underground lines or water lines can be damaged when those lines are being repaired.