Pruning Techniques

• Alternatives • Tree Removal
Why Must Trees be Pruned? Pepco is committed to providing our customers safe, reliable electricity in a cost-effective manner. Pruning, or trimming, trees is one of the key services that allow us to deliver electricity – and it is a vital activity that directly affects public safety! Tree problems can easily cause power outages, which we strive to eliminate. Keeping trees properly pruned also minimizes the possibility of electrical contact, downed wires, and electrical fires, all of which can be dangerous to the public, in addition to damaging or killing healthy trees. An effective tree maintenance program is critical to our successful delivery of your electric service.
Directional or Lateral Pruning The term “lateral” is derived from the method of cutting a branch back to the next limb or lateral growing branch (see Figure 2), which mimics the way trees self-prune their branches in a forest. This reduces the number of fast-growing, multiple sprouts and directs the future growth of the tree away from the power lines. Lateral pruning involves removing only the branches that may endanger electrical wires. This selective pruning of specific branches retains more of the trees natural crown, a method proven to be healthier for the tree than arbitrary topping.
		When the tree is located to the side of the power lines, branches growing toward the wires are pruned as well as branches that could grow over the top of the the wires. Subsequent pruning will reinforce the directional training of the tree.
Wire location, limb size, or branch configurationlimb size, or branch configuration may make it necessary to remove limbs back to the tree’s trunk. The tree species, its position in relation to our electric facilities, and line voltage are all factors in determining how much limb removal is required. Figures 3 and 4 show the basic forms that lateral pruning can take depending upon where the tree is in relation to the power lines. When trees are planted directly beneath power lines, branches must be cut back until a fork (crotch) in the tree is reached (see Figure 3). This is a natural junction that allows the arborist to direct new growth away and permits large trees to coexist with power lines.
		Trees planted directly below power lines pose the biggest risk to the power supply. Branches growing in the direction of the wires are pruned until a clear passage on all sides is created. Future growth is directed away and down
If the tree is next to power lines, then lateral cuts are made to direct the tree growth back and away from the power lines (see Figure 4). Branches above the power lines are directed up and back, while those below the power lines are directed down and back or removed to the trunk. Next season’s growth is then concentrated in the direction of the lateral cuts and away from the wires. Future pruning refines this procedure andimproves the shape of the tree. These methods usually mean cutting fewer branches but achieving better electrical service reliability for our customers, and it is healthier for the trees.
		When the tree is located to the side of the power lines, branches growing toward the wires are pruned as well as branches that could grow over the top of the the wires. Subsequent pruning will reinforce the directional training of the tree.