---

Getting to the Root of It

Trees spread their roots farther than you may think

Among homeowners, planners, contractors and others who work with the ground, the Bay Gardener has noticed a lack of respect for the roots of trees. It’s common to see asphalt or cement spread to within inches of a tree trunk. Near construction such as buildings or walls, it is not uncommon to see several feet of soil piled around the base of trees three to six inches in diameter.

Roots are vital to the survival of trees.

If a tree is 50 feet tall, it will spread its roots at least in a 50-foot radius around its base. Roots typically extend far beyond the drip line, the area directly beneath the tips of the branches.

An extensive study conducted at North Carolina State University many years ago established that the roots of the tulip poplar tree actually extend one and a half times its height. So a tulip poplar tree that is 50 feet tall will have roots extending at least 75 feet in an underground radius around the base of the trunk.

For homeowners, this means that anything done to soil under the branches of a tree and beyond influences a tree’s growth. Since 90 percent of trees roots establish in the upper 10 inches of soil, dumping additional soil over the roots causes them to suffocate. Tree roots are shallow because they need oxygen to survive. The deeper the soil the less oxygen. Driving automobiles, trucks or heavy equipment over roots will cause soil compaction, which also suffocates the roots.

Be kind to tree roots, and you’ll be rewarded by abundant shade and increased value of your property.

Oak Leaves Make Fine Compost

Q We have three oak trees in our front yard, each about 18 inches in diameter, measured at chest height.

First, I don’t know what kind of oak they are.

Second, what should I do with the leaves? Since oak leaves are so acidic, I’ve been raking them off the lawn each fall and carrying them to our woods. I would feel better if I were utilizing the leaves, but how? Last fall I chopped some up with the lawnmower and placed them around the azaleas as mulch, but I have way more leaves than azaleas. I don’t have a compost pile.

Thanks for your help. Keep up the good work on your column in Bay Weekly.

— Lisa Petersen, Owings

A You appear to have a burr oak.

Oak leaves are no more acid than maple, ash, linden, etc. I have two large cherry-bark oaks in my yard, one six and a half feet in diameter and the other three feet eight inches. I rake as many of the leaves under the shrubs as possible and the rest I place in the compost. I did research back in the 1980s for the purpose of stopping that myth about oak leaves being acid.

Ask Dr. Gouin your questions at [email protected]. All questions will appear in Bay Weekly. Please include your name and address.

© COPYRIGHT 2007 by New Bay Enterprises, Inc. All rights reserved.