Question: Huge roots stick up above the lawn under my tree. I want to fill soil between the roots and lay sod on top. Is this a good idea?
Answer: That depends on whether the roots are on the surface because of erosion or because the soil is compacted and they are coming up for air. If soil has washed away, you can replace it. Tree roots will suffocate if they are buried under too much fill dirt. They can tolerate a few inches of added soil. The trees most sensitive to change in soil grade are: beech, dogwood, oak, pines, spruce, sugar maple and tuliptree. Where fill dirt would be too deep, plant a ground cover or mulch. When you are calculating the depth of the fill dirt, add in the half-inch of soil that the sod includes. Roots seeking oxygen because of compacted soil should not be covered at all. It is best not to fight nature. Plant ground cover or mulch between the roots.