Simple steps worth it, given many benefits of trees
Building or remodeling? Protecting your trees now can save you time and money later
As of this year, the U.S. has a total resident population of 314 million, with about 250 million of those people living in or around urban areas. Portland and other urban areas in Oregon continue to grow as well, but often times the construction projects associated with growth are less than kind to our neighborhood and community trees.
What's at stake? Our urban forests, comprised of native forest remnants and the planted forested landscapes in our cities. These trees provide us a vast array of benefits including clean air and water, lower crime rates, even higher residential and commercial property values.
Trees remove particulates, nitrogen dioxide and other pollutants from our air. They slow water runoff and ensure that groundwater supplies are continually being replenished. Their mere presence raises the property values of homes with trees vs. those without, and the shade they provide helps us lower our energy bills in the summer. Studies even show social benefits, such as less crime in tree-filled neighborhoods, and shorter recovery times for hospital patients with a view of trees.
What are the more common ways trees become damaged during construction, and what simple measures can we take to protect them?
Torn bark and branches
Trucks, graders and equipment can injure a tree by tearing bark, wounding the trunk and breaking branches. These injuries often prove fatal later on. By all means, work to prevent trucks and machinery from injuring trees' crowns or trunks. Plan ahead by talking to all workers on site about tree protection.
Protect the soil
Compaction of soil is a severe problem where trees are concerned because their roots need oxygen, nutrients and water to grow. That's why, if soil becomes compacted around a tree, it's only a matter of time before the tree will decline and die. Placing 4 to 6 inches of mulch or wood chips into the "drip zone" around the trees will help, as will placing construction fencing around all trees that are to remain.
What's the drip zone? It's the circle that could be drawn on the soil around a tree directly under the tips of its outermost branches.
Another pointer: make sure any protective fencing is placed as far away from the trunks of trees as feasible, and require the fence to remain in place for the life of the development project. Also, protect soil horizons in the surrounding landscape by avoiding soil disturbance as much as possible. Maintaining early communications with the builder and workers early on is key.
Protect the tree's roots, which extend quite a ways out from the tree.
A tree's roots are found mostly in the upper 6 to 12 inches of the soil, and in a mature tree, extend far from the trunk. In fact, roots can be found growing a distance of one to three times the height of the tree. Cutting or disturbing a large percentage of a tree's roots increases the odds of the tree's failure or death; the amount of damage a tree suffers from root loss depends in part on how close to the tree the cut is made. Also, remember that tree roots larger than 4 inches in diameter are usually structural roots, and cutting them creates a potential for the tree to fall over later on.
Again, be careful not to smother the roots by adding soil. Tree roots need air to breathe and grow and it takes only a few inches of added soil to kill a sensitive mature tree.
Sometimes, irrigation pipes and other projects mean cutting through a tree's roots is unavoidable. If this is the case, use sharp tools, and never tear the roots with a backhoe. You can place damp burlap on roots that are left next to a trench; also, after a lot of root disturbance, be sure and give the tree extra watering on a regular basis. Lastly, after root disturbance don't prune your tree for at least a year your tree needs all its leaves to regenerate its roots.
Consult a certified arborist
Protecting trees during remodel, construction or development projects saves money on long-term tree maintenance and replacement costs, provides aesthetic benefits and generates positive response from neighbors and the community. However, it's not usually wise or feasible to try and save every tree.
If in doubt, consult with your city forester or a certified arborist to help you with the evaluation process.
For more information about tree care, or finding a certified arborist:
Cynthia Orlando has a degree in forest management and is a certified arborist and public affairs specialist with the Oregon Department of Forestry.