Maintaining the proper clearance between wires and trees is important because on windy days, both branches and wires sway; during the winter, the ice and snow on the branches causes them to droop toward the wires; on very hot days, the combination of electric load and the outdoor temperatures causes the wires to sag. In these cases, the potential for contact, and interruptions in electric service, greatly increases.
When branches come in contact with high-voltage conductors, they can open wounds on the tree, which become access points for bacteria, insects, parasites, fungus, etc., and the flow of electricity could damage the pathways for nutrients within the trees. For more information, see the link https://nj.pseg.com/safetyandreliability/reliability/treetrimming/distribution.
