Trees, especially mature ones, can add thousands to your property value, not to mention energy-saving shade, attractiveness and the lulling whisper of wind in the leaves.
When you consider it can take a lifetime to grow one, it’s worth your while to protect them, even as you improve your property. If your work involves affecting the earth or grade around a tree, here’s a few things you should understand.
The root system of most trees extends from the trunk roughly as far as does the canopy of leaves. This is the drip line. So avoid, if you can, excavating underneath overhanging branches. You can tighten this area by careful pruning of branches and roots, but you may want a professional to help you.
Adding topsoil and regrading can also be damaging. By no means should you pile any more than 8 inches of earth against a tree’s trunk, and you should actually try to avoid adding topsoil to any of the area within the dripline. This is because the roots have already grown at the proper depth. Adding soil changes the oxygen content of the soil and can even raise the water table. That’s bad news for the roots.
But you can regrade and save your tree with a tree well and a drainage/breather system. This consists of four to six perforated ABS or PVC pipes radiating like spokes from within a foot of the tree to a few feet beyond the drip line. Each spoke is joined to its neighbors by pipes which form a “rim” around the circumference. And a vertical “breather” pipe runs from the end of each spoke up to grade level. Next, you build a dry-stone or concrete block retaining wall around the trunk, and only then backfill the area.