I have a large and established tree with some surface roots. What would happen to the tree it I piled up earth to make a mound in its root area?
Of course, I would keep the dirt away from the stem— probably by about ten feet.
How close to the tree could I dig? Or in other words, how many roots can a tree afford to loose? I know any standard rule in this case would only be a generalization, but I would be interested in what people have done or seen.
Location: Western Kentucky-Climate Unpredictable Zone 6b
posted 4 years ago
What type of tree ? Some species have very shallow feeder roots that run quite a distance from the trunk . Birch , for instance . They would not tolerate loss of feeder roots as well as deep rooted types .
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As an arborist, one of the things that I see most that is detrimental to trees is grade changes and root impact. What you see in the air on the tree is nothing without the vast network of roots and fungi in the soil. Disturbing that balance can often be the thing that sends a tree into a spiral of decline and an untimely demise. Often times the stress of root impact and grade change is what attracts insects that then attack and kill trees. I would recommend not doing grade changes under the drip line of the tree (the point that a drop falling from the outermost tips of the tree would land) or if you do, make them very minimal and do them incrementally over multiple years. Never backfill around the stem or the root flare at the base of the tree.
Having a consulting arborist look at the tree in question is always a good first step. That might tell you how long lived the variety it is and what kind of stress that variety can typically take in your environment. I am curious what variety it is as well.
We did a grade change around a sugar maple tree. We used boulders pretty much at the drip line, and mounded up soil beyond those. Maples are really active with the surface roots and seem adaptable, to me. A decade previous I piled mulch all around the trunk (OK, not touching the trunk, but giving it a big mulch circle) and it sent roots up into the mulch over time. An oak tree can be killed with just 6 inches of dirt if you cover up too much of the root mass, or so I've been told.