Pamela J. Bennett, Ohio State University Extension, Clark County.
Planting Depth
Tree planting issues continue to remain in the forefront on BYGL conference calls. There were several reports regarding trees planted with the root flare well below the soil surface, or soil being added to the surface of established root systems.
When preparing the depth of the hole, first check for evidence of flaring buttress roots. This may mean that soil should be removed to determine the location of the root flare. Plant trees at the level of the exposed buttress roots or the root flare. In some cases, trees are planted so that the root flare is slightly above ground level.
In relation to planting depth, the issue of adding soil on top of the root system of trees was discussed. Gardeners have the tendency to want to design flowerbeds under trees; they sometimes accomplish this by adding soil around the base of the tree, adding more soil over the root system of the trees.
Planting trees too deep and/or adding soil to existing grades of trees leads to reduced oxygen levels for tree roots. Roots suffer from the lack of oxygen, leading to branch dieback. This may occur over a period of time, depending on the overall health of the tree. The extent of the injury depends on many variables, including species, age, and condition of the tree; the depth and the type of fill; drainage; and subsequent exposure to insect and disease pressures.