Option one: The best treatment for trees planted too deeply is to replant at the proper depth. Dig the tree as you would transplant it, remove soil and surface roots growing above the root flare, and set at the proper depth.

Option two: If trees are only several inches deep, soil can be removed from the root flare as shown in the photo above. When you reach the root flare remove soil that is on top of the main surface roots as far out as practical. Many roots may be growing up toward the soil surface; remove any that circle, bend more than 45 degrees, or cross over the main roots that emerge from the trunk.

Create a saucer of sorts 8 to 12 feet wide centered at the trunk pulling all soil away from the trunk. Place a 2-3 inch thick layer of organic mulch in the saucer but not on the trunk. The problem with this approach is that rain, wind, gravity, mowers and animal activity will slowly move the mulch and soil back to refill the saucer.