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Trees and the Urban Environment

W. Kirk Shearer

Trees in the urban landscape are highly important and very much prized by both private residential and commercial property owners. They give many benefits such as shade during hot summers that reduce cooling bills, help to screen traffic noise and peering eyes, reduce air pollutants, provide oxygen, and habitat for wildlife, add value to your property, and when healthy and properly located, greatly increase the overall aesthetics of the surrounding area. In the utility arboriculture field, there is a saying that has become a cornerstone of an extensive public education program and that is "The Right Tree in The Right Place."

When choosing a planting site, property owners (and unfortunately many landscape professionals as well) will look only at a spot on the ground without examining the vertical space also. As you might imagine, trees whose height and crown diameter at maturity are greater than the space available are impeded in their crown development and may cause any number of problems for the property owner. With just a little planning and research, most people can avoid a majority of these problems by properly selecting a tree for particular site based on the area conditions, available space, and individual species characteristics.

Residential lots in an urban environment can vary in size and shape a great deal, but there are a number of conditions universal to all. Before selecting a suitable planting hole for a tree, an individual should consider the proximity of driveways and sidewalks, utilities - above and below ground, and also how close to the house or building's roofline. Roots can damage underground pipes and sidewalks, and if the available area for tree crown development is reduced by planting too close to other trees, buildings, and especially high voltage power lines, the individual may be forced into hard decisions or suffer regret because of an ill-advised planting site. In the instance of power lines, pruning becomes a necessity due to public safety requirements. Obviously, you wouldn't want to plant a bald cypress, loblolly pine, or tulip poplar directly under high voltage conductors only 40 feet high since these are species with a dominant leader, and a tree trimming contractor has no choice but to 'top' the tree, forever changing its shape and in my opinion, ruining its natural form. Trees do not need us to teach them to grow; trees are pruned and shaped only because that is what we either choose or must do.

In a city environment, it is wise to consult a local, certified arborist with a good working knowledge of the prevalent tree species in the area, and also may be familiar with city and county ordinances concerning 'street' trees. Many cities across the United States now employ full time Arborists and Foresters whose job it is to preserve urban trees and provide public safety through routine maintenance. Trees that homeowners consider their own responsibility may actually 'belong' to the city and are their responsibility. Consulting Arborists should be called any time there is an issue of safety and tree health or maintenance. Depending on their experience and certification, the individual may or may not be aware of the requirements concerning clearances required around electrical conductors and may or may not be Utility certified. If clearance around high voltage conductors may be an issue, it is best to ask the professional up front if he is line-clearance certified, or you should also call your electric service provider and they will determine if trimming is necessary.

A common question is "Who is responsible for trimming trees around the power lines?" In general, the electric company or its appointed contractor is responsible for maintaining the required clearance around high voltage conductors. However, once the power leaves the pole out by the street on its way to the house (here voltage is stepped down through oil-filled transformers) trimming along the 'service drop' becomes the property owners responsibility. While a much lower voltage, this line is still highly dangerous and before any trimming is to be done, homeowners should call the utility and they will temporarily disconnect power so tree trimming may be done safely. Numerous fatalities happen each year because of foolish mistakes by inexperienced individuals unaware of the inherent danger. As for other lines on utility poles such as telephone and cable TV, these carry a minimum charge and trees are usually not trimmed to maintain clearance. The easiest way to tell them apart is to identify the lines located highest on the pole as these always the carry highest voltage and are mandated to be a certain height; telephone and cable TV lines will be found much lower and appear to be coated.

Arborists and tree workers certified by the ISA (International Society of Arboriculture) study and follow a high set of standards in the care and maintenance of trees. The "stubs" commonly seen after poor pruning of tree limbs are not recommended and only open the tree to disease and rot.

Other common concerns are those surrounding liability and urban trees. If a tree blows over it would be considered an 'act of nature', unless further investigation shows the tree to be dead, rotten, or some other obvious hazard that was never addressed by the rightful owner. When hiring a tree trimming or removal contractor, consumers should always ask to see current proof of liability insurance AND the limits provided. Limits required can vary by state, and may be as little as $100,000. A Professional intent on protecting his business and customers will carry limits of at least $1,000,000 or higher - anything less in this author's opinion is completely inadequate.

Spotting damage and decay in trees can be very difficult, and is almost as much art and intuition as science. Many times the decay is hidden from view and cannot be detected without the use of sophisticated equipment. Most tree species are resilient (the popular Bradford Pear for instance is not, due to its poor crown shape and 'dog hair' limb structure) and can oftentimes recover from damage such as broken limbs due to a windstorm or even a lightning strike - depending on the extent of the damage and overall health of the tree. It is wise to watch for signs of decline afterward such as dieback or leaf loss, and insect attacks before deciding whether a tree is done for, or merely needs a good maintenance pruning. It may become necessary or even preferable to remove a tree in the end, but stumps can be ground up or landscaped around. Some species will sprout from the stump and may need to be treated with an herbicide to prevent this.

Below is a tree hazard checklist, courtesy of the National Arbor Day Foundation. Readers are encouraged to visit the National Arbor Day Foundation's website for a extensive information including a handy guide to tree planting: www.arborday.org/trees/righttree.html. This website has many pages of useful information including a list of trees and their corresponding characteristics. To contact a Certified Arborist in your area, please visit the International Society of Arboriculture website at: www.isa-arbor.com/.

Tree Hazard Checklist

Consider these questions...

1. Are there large dead branches in the tree?
2. Are there detached branches hanging in the tree?
3. Does the tree have cavities or rotten wood along the trunk or in major branches?
4. Are mushrooms present at the base of the tree?
5. Are there cracks or splits in the trunk or where branches are attached?
6. Have any branches fallen from the tree?
7. Have adjacent trees fallen over or died?
8. Has the trunk developed a strong lean?
9. Do many of the major branches arise from one point on the trunk?
10. Have the roots been broken off, injured or damaged by lowering the soil level, installing pavement, repairing sidewalks or digging trenches?
11. Has the site recently been changed by construction, raising the soil level or installing lawns?
12. Have the leaves prematurely developed an unusual color or size?
13. Have trees in adjacent wooded areas been removed?
14. Has the tree been topped or otherwise heavily pruned?

Kirk Shearer, a native of Mississippi, received a B.S. degree in Forest Resources Management from Humboldt State University in Arcata, California in 1997. Since then he has worked in Timber Management for the United States Forest Service, and spent three and half years as a Property and Casualty Insurance Agent in Ridgeland, Mississippi. A Certified Arborist since 1999, he is currently a Project Manager for Western Environmental Consultants, Inc., in San Jose, California. WECI and their parent company ECI, based in Southampton, Pennsylvania are Vegetation Management Contractors providing consulting services to electrical utilities nationwide, as well as England, Australia, and New Zealand.