Preserving our Valuable Trees

Preserving our Valuable Trees

Does your property have a mature, beautiful tree? In addition to being aesthetically pleasing and creating safer environments, modern society is valuing these trees in new ways. Trees reduce storm water runoff and flood potential by capturing the first 30% of precipitation in their leaves and absorb another 30% in their root structure. Increased pavement longevity, lower urban air temperatures, improved air quality, higher property values, reduced urban traffic speeds – the list goes on! In seeing these benefits, it is not surprising that a tree can return over $90,000 in direct benefits over the lifetime of the tree. [1] Did you know that a lack of foresight and planning during landscaping or home improvements can damage these valuable resources? Early planning during the development design stage can protect existing beneficial trees.

Soil compaction and root damage are two of the main threats to urban trees. In order to prevent this, it is critical to establish Protected Root Zones (PRZs) for all the trees planned to be saved in your project. Once the PRZ is established, install a physical barrier (snow fencing, polypropylene, etc.) around all the trees to ensure their protection throughout the project.  To calculate the PRZ do the following[2]:

  1. Measure the diameter (width) of the trunk at chest height, to the nearest inch by wrapping a tape measure around the trunk and dividing that measure, in feet, by three.
  2. Multiply that number by 1.5 for mature or stressed trees or by 1.0 for young, healthy trees. Calculate your result in feet.
  3. Take the calculated value and measure that distance from the trunk of the tree. The area within this radius is the Protected Root Zone (PRZ).

It is recommended that you consult an arborist to help insure the likelihood of the tree’s survival. Prior to working within the RPZ, make sure the trees are well watered and try to avoid work on hot, dry days. Minimize compaction as much as possible by not storing materials within the RPZ. Actions that require the cutting of tree roots should be done quickly with clean cuts so that the wound closes and regenerates quickly.  Exposed tree roots should be covered as soon as possible with mulch, soil, or dampened burlap in order to minimize stress to the tree. If there needs to be adjustment to the soil level in within the RPZ of a tree, extreme care must be taken as the addition or removal of as little as 2 inches of soil in the RPZ can kill a tree. Finally, concrete surfaces and walkways should be placed at least 3 feet from the anticipated edge of a mature tree trunk.

Though it was said long ago, this sentiment holds true today:

A society grows great when old men plant trees whose shade they know they shall never sit in.

[1] 22 Benefits of Urban Street Trees by Dan Burden, Senior Urban Designer, Glatting Jackson and Walkable Communties, Inc; May2006.

[2] Tree Owners Manual for the Northeastern and Midwestern US by the US Forest Service.

Have a comment? Join us on Facebook!