Tree Roots Need Oxygen
An important influence on how deep a tree’s roots grow is the oxygen level in the soil. Heavy soils, such as compacted clay, have limited pore space and low oxygen levels. Tree roots need oxygen, so those growing in compacted clay tend to grow close to the surface. When dealing with a tree root that has surfaced, the first inclination may be to cover it with more dirt, but is this the best solution?
Probably not. When the roots are covered up, most trees will either show stress or resurface their roots.
Here are a few suggestions for protecting surfaced tree roots:
-Enlarge the bed or island around the tree so that the surface roots are not in turf areas.
-Cover the surface roots with 2-3 inches of organic mulch
-Cover the roots with only 1-2 inches of very good quality topsoil.
-Make sure the root flare is visible.
-Never cut/remove larger surface roots.
-Do not attempt to hide the roots by building a raised flower bed or box.