Got Nature? Blog

Question: I have two White Ash trees growing in my front yard along the street. One is 8″ in diameter and the other 12″. Large roots are growing out of the ground horizontally away from the trees. Should I try to cut these roots and risk hurting the tree or should I try to mound dirt over them to allow grass to grow? The roots are unsightly and ruining my lawn.

Answer: Trees provide many benefits including clean air and water. Also, they can provide up to 10% greater property value by keeping trees on your site healthy. First, make sure they are treated against Emerald Ash Borer to prevent from losing them to the pest.

Tree roots can grow a great distance from a tree, sometimes two to three times the height of the tree. These are very important for stability and health. Cutting tree roots can be a very risky choice as well as covering them with soil. When you cover existing tree roots with soil the results are similar to smothering the tree by not allowing gas exchange between the roots and the air above.

I would suggest not doing anything to the roots within the drip line of the tree. Outside of this critical root zone area is less risky and changes can be made with minimal risk. The best option under the drip line would be to add a light layer of two to three inches of hardwood mulch creating tree rings to help the tree, reduce mowing and cover the roots.

Resources:
When Tree Roots Surface – Purdue Extension
Emerald Ash Borer in Indiana – Purdue Extension
Mechanical Damage to Trees: Mowing and Maintenance Equipment – The Education Store, Purdue Extension Resource Center
Why Is My Tree Dying? – The Education Store
Tree Owner’s Manual – Indiana Department of Natural Resources

Lindsey Purcell, Urban Forestry Specialist
Purdue University Department of Forestry and Natural Resources