Cynthia Orlando
Oregon Department of Forestry
Building or remodeling? Protecting your trees now can save you time and money later.
Trees provide a vast array of benefits including clean air and water, lower crime rates, even higher residential and commercial property values.
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.
Hard ground, fences and more
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.
The “drip zone” is the circle that could be drawn on the soil around a tree directly under the tips of its outermost branches.
Watch out for roots
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.
Consult a certified arborist
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, visit http://www.treesaregood.com or http://www.pnwisa.org/hire-an-arborist.html
Cynthia Orlando has a degree in forest management and is a certified arborist and public affairs specialist with the Oregon Department of Forestry.