Questions about Trees and Utilities
Why is the utility company “butchering” our trees?
- Pruning trees along overhead utility lines reduces electrical interruptions, provides safe conditions for the public, and protects power company employees. Most interruptions during storms are caused by trees. One type of service interruption, called a momentary interruption, is annoying to the customer because it lasts just long enough to affect sensitive electronic equipment such as clocks, VCRs, and computers. A second type, called a sustained interruption, results in a complete loss of power. Sustained outages occur mainly during severe weather, and may cause serious damage to electric facilities.
- The utility company hires contractors whose trained tree workers clear vegetation back to distances that are consistent with safe and reliable electric service. Clearances between trees and wires vary according to different voltages of primary and secondary conductors. Also, pruning practices may differ between urban and rural areas. Most utilities use an arboriculturally correct method called directional pruning, instead of topping and shearing. Directional pruning directs subsequent growth away from wires and leaves no stubs. Even a properly pruned tree growing near wires may have a disfigured appearance.
Can’t wires be buried underground, to get them out of our trees?
- In new developments, electrical conductors usually are placed underground. But to relocate existing wires from poles to an underground installation would be prohibitively expensive. Besides the expense to the utility company, property owners would have to dig up their yards and relocate the electrical entrance to each building at a cost of several thousand dollars. Moreover, the trenching would tear up tree roots, which could injure or kill the trees. Future maintenance of underground utilities can be disruptive to established landscape plants, and repairs would result in longer outages.
How can the conflict between trees and wires be resolved?
- The best long-range solution is to replace incompatible trees (those that interfere with wires) with new trees that will not grow into wires. Trees can be replaced all at once, or one at a time as trees become overmature and unhealthy. The choice between sudden or gradual replacement depends on various considerations, including the type of landscape desired in a neighborhood. A formal design with uniformly spaced trees of the same kind and size requires planting all trees at the same time. An informal planting design can be implemented over several years, with less disruption in the appearance of the neighborhood.
- The design concept of trees that are compatible with utility lines has been called “the right tree in the right place.” The right tree for planting under utility wires is a species that will not be taller than 20 to 30 feet at maturity (Table 1). Medium-size trees, up to 45 feet at maturity (Table 2), can be planted near utility lines if they are offset at least 15 feet from the nearest wire. Adequate space for root growth also is an important consideration when deciding tree size and placement. Low-growing trees are most appropriate if the space for roots between the curb and the sidewalk is less than 4 feet wide. If pedestrians and vehicles pass by the planting site, the variety selected should have ascending branches and a single trunk that can be pruned up for clearance.
|Common Name||Scientific Name||Mature
|choke cherry, Shubert||Prunus virginiana Shubert||20-30||15-20|
|Adams, centurion, harvest Gold, madonna, Prairifire, Prof. sprenger, red Barron, red Jewel, sentinel, snowdrift, spring snow, sugar Tyme, Zumi, or redbud||depends on variety|
|dogwood, kousa and hybrids:||Cornus kousa and varieties:
|celestial, constellation, Julian, milky Way, stardust, steeple, stellar Pink|
|hawthorn varieties:||Crataegus varieties:||15-30||12-35|
|crimson cloud, inermis, ohio Pioneer, phaenopyrum, Vaughn, Winter King||depends on variety|
|Japanese tree lilac varieties:
Ivory Silk, Regent, Summer Snow
|Syringa reticulata varieties:
|Autumn Brilliance, cumulus, majestic, Princess diana, robin hill, Tradition||depends on variety|
|Common Name||Scientific Name||Mature Height||Mature Width|
|birch, Heritage||Betula nigra heritage||40-50||30-40|
|cherry varieties:||Prunus varieties:||25-40||12-35|
|Accolade, Kwanzan, Okame, Rosy Cloud, Sargent columnar||depends on variety|
|corktree, Amur, varieties:
|Phellodendron amurense varieties:||35-45||30-40|
||Gleditsia triacanthos Imperial||30-40||35-45|
|hophornbeam, American||Ostrya virginiana||30-40||20-30|
||Carpinus betulus fastigiata||40-50||30-40|
||Aesculus x carnea||35-50||30-45|
|maple, Crimson King||Acer platanoides Crimson King||40-50||35-45|
||Acer platanoides Olmsted||35-45||20-25|
|maple, Norwegian Sunset
||Acer truncatum Norwegian Sunset||35-45||25-35|
|maple, Pacific Sunset||Acer truncatum Pacific Sunset||30-40||25-35|
|maple, Queen Elizabeth||Acer truncatum Queen Elizabeth||30-40||25-35|
|pagoda tree varieties
Halka, Regent, Princeton Upright
|Sophora japonica varieties:||40-50||25-40|
|pear, callery, varieties
||Pyrus calleryana varieties:||35-45||12-35|
|Aristocrat, Autumn Blaze, Capital, Chanticleer, Cleveland Pride, Cleveland Select, Valiant, Whitehouse||depends on variety|
Can’t we have any large trees?
- Yes, many residential neighborhoods and other locations can and should accommodate properly placed large trees. Utility lines usually are along just one side of a street; large trees can grow on the opposite side if there is ample space for the roots and branches. Other open spaces away from the street also can accommodate large trees, though they should be planted far enough away from buildings. In fact, a diverse mixture of tree sizes and species tends to be healthier, with fewer disease or insect problems. Large trees are recommended where space permits, as they contribute most to cleaner air, moderating temperatures, and reducing storm water runoff.
Who can answer my other questions?
- Contact your local utility, Penn State Cooperative Extension office, or Pennsylvania District Forestry office.
Produced by Henry D. Gerhold, professor of forest resources, and William F. Elmendorf, instructor of urban and community forestry.
TitleQuestions about Trees and Utilities
SeriesUrban and Community Forestry in Pennsylvania 7
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