Tree Roots Cause Problems with Mowing
Marianne C. Ophardt
Washington State University Extension
Area Horticulture Specialist
Roots of large shade trees such as silver maple, sycamore and others often create problems when mowing the lawn. Does it hurt the tree to cut the big roots off? Would it be better put some soil over the top of the roots to make the surface nice and smooth?
Neither of these is a good solution to the mowing problem. Severing of large, major tree roots will significantly impair that tree's ability to absorb water and nutrients from the soil. Removal of large roots also weakens the tree structurally. Remember the large woody roots help to anchor the tree.
Raising the grade around the tree more than one or two inches can smother the fine feeder roots on a tree. Roots can't live without oxygen and even several inches of soil can hurt the roots of certain trees. Deeper soil piled around the trunk of the tree can lead to rot at the base of the trunk... leading to tree decline and death.
Unfortunately, there is no good or easy solution to your problem. You might try killing the grass and mulching the area with bark mulch, being sure to keep the mulch several inches away from the tree trunk.