Making Room at the Top

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Published on: Apr. 2, 2000

Last revision: Nov. 4, 2010

Tree and utility wires have always vied for space in our rural and urban areas. No clear winner has emerged from this competition. We either were faced with electrical outages caused by broken tree branches, or our roads were lined with disfigured, high-maintenance trees. Today, however, most utility companies are using an improved method of pruning that can help protect the health and safety of trees and provide the necessary clearance for electrical distribution wires. Electric utility companies must provide continuous service for our needs. To guard against power outages, they must regularly remove tree branches that threaten wires. Traditionally, utilities have cut the branches back to a point that would allow needed clearance. Called heading or topping, this method efficiently, if temporarily, protects wires, but the trees suffer enormously.

Topped or stubbed-off branches usually produce numerous fast-growing shoots, which are weakly attached and subject to future breakage. These shoots also grow directly back into the space needed for utility wire clearance. The branch stubs holding the sprouts are left vulnerable to decay, which may progress down into the branches and weaken them.

This will happen even if the sprouts growing from these branches produce seemingly luxuriant foliage. Some trees cannot tolerate drastic removal of branches and may quickly decline. The entire process of repeated topping virtually ensures a population of unhealthy trees. Weakly-attached or decayed branches are susceptible to breakage, especially during wind or ice storms.

Some people mistakenly think the heading or topping technique is acceptable or even desirable for all trees. Countless trees throughout Missouri have suffered irreversible damage from topping by people with perfectly good intentions, even when such drastic treatment was not needed.

Today, many utility company's approach to clearance of electrical transmission wires continues to involve regular maintenance pruning, but cuts are made in such a way that whole branches or limbs growing towards wires are removed, leaving no stubbed-off branch ends. Names given to this utility wire clearance technique include natural target pruning or, more specifically, natural directional pruning.

This technique benefits trees because it is more sympathetic with their natural growth habit. Wounds from cuts made at branch collars, or at their point of attachment, grow over more easily, minimizing decay. Excessive sprout growth is avoided because most live branch ends are left on the tree to sustain future growth.

Utility companies benefit from natural directional pruning because over time trees are more sound and less susceptible to breakage.

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