Planting depth and soil amendments affect growth of Quercus virginiana Mill.

The effect of planting depth, defined as the location of the root collar relative to soil surface, is of particular concern for tree growth, development, and performance in the landscape and seems to be dependent on soil conditions. The objective of this study was to determine the effect of three planting depths and four soil amendments on live oak (Quercus virginiana Mill.) growth and visual quality. Trees were planted with root collars at one of three planting depths (grade, 7.6 cm above grade, or 7.6 cm below grade). Soil amendments were: incorporated sand (30% by volume), incorporated composted peat (30% by volume), sandy topsoil in raised (20 cm) bed, and native sandy loam soil (control). Planting at grade or below grade resulted in 0% mortality, while planting live oak trees above grade resulted in 12.5% mortality. The container produced trees were top-heavy (high shoot:root ratio) and were thus susceptible to wind damage when planted above grade. Trunk diameter growth and relative growth rate were smaller when trees were planted with root collars below grade compared to those planted above grade or at grade. Visual quality of live oak roots was improved when trees were planted in raised beds with sandy topsoil compared to the control soil. Shoot visual quality was improved when trees were planted in the incorporated sand and raised beds with sandy topsoil compared to the control and incorporated peat sections. Thus, it is recommended to plant live oaks with the root collar at grade and in sandy top soils in raised beds to improve tree quality after establishment.