How to Change the Grade Around a Tree

If construction or extensive landscaping is taking place around existing mature trees, it's often necessary to raise or lower the soil level around the trees. Any change in the grade can easily kill the trees. Take steps to ensure your tree's survival while during the transition. Just follow these steps.

Instructions

Difficulty: Moderately Challenging

Raise the Grade

1. Remove all vegetation around the tree. Leaving organic matter on the area to be filled can create noxious gases that might harm the tree.
2. Cultivate the soil. The top 3 to 6 inches of soil should be broken around the tree to allow water to continue flowing to the root system. After this is done, fertilizer should be applied.
3. Construct a well. A dry stone wall (not mortared) should be constructed at least 1 to 2 feet away from the trunk of the tree. This wall should extend up as far as the new soil level will reach.
4. Add drainage pipes. Use 4-inch perforated plastic pipes. These pipes should radiate out from the center of the tree and beyond the drip line of the tree. The outer edge of the pipes can be connected with more perforated pipe to form a circle around the tree.
5. Attach vent pipes. Vertical pipes extending up to the new grade level should be connected to this outer circle. Use gravel to hold them in place.
6. Fill the area. Use a bottom layer of crushed stone and then a top layer of gravel to fill over the drainage system. A landscape fabric or other porous material should be placed over the gravel layer to prevent soil from mixing with the gravel. Add several inches of topsoil over the fabric.

Lower the grade

7. Excavate around the tree. Come no closer to the tree than the drip line. This is the point where most of the water will run off the tree when it rains. If the path of the water is obstructed from reaching the roots, the tree will be damaged. Excavate even further out if you can. Excavate to the depth of the anticipated level of the new grade.
8. Build a retaining wall. The wall around the tree will hold the soil in place, protecting the roots. Whatever material you use for your wall, be certain that good drainage is provided.
9. Trim the tree. The tree lose some of its root system, and pruning will help it recover. Retain the natural shape of the tree while trimming it to half its original size.

Tips & Warnings

• If a tree has already lived out its normal lifespan, or has been damaged, it may not be worth the effort and expense to replace.
• Make sure that water can drain away from the tree once your final grade is completed.
• Add gravel to the inside of the tree well and to the vertical vent pipe to keep rodents out of the system. You may need screening material for this.

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