Newly transplanted trees and shrubs in urban areas frequently encounter compacted soils with disturbed horizons, competition for space with underground infrastructure, pollution, excessive heat, high foot traffic, and are often neglected in terms of irrigation and fertilization. Root growth into the surrounding soil is vital to plant survival and establishment. To make the plants attractive for purchase, nursery-grown plants are often heavily irrigated and fertilized to encourage rapid shoot growth. Once transplanted, it may be difficult for the plant to compensate for evapotranspiration from these abnormally large canopies using only the resources available in the root ball, whereas at the same time allocating energy to root growth. In such difficult growing situations, many of these plants do not survive (Day et al., 1995). In both horticulture and urban forestry, most research on plant performance in constructed urban landscapes is performed on trees. Although this is important, research on successful transplanting of the woody shrubs that constitute the backbone of many landscapes is also imperative.
Studies on planting above-grade have proven it to be a successful technique, both with trees (Arnold et al., 2005) and woody shrubs (Wright et al., 2007). Wright et al. (2007) described a modified above-grade planting technique in which the upper portion of the root ball remained above the soil surface, and PB was mounded around the above-grade portion of the root ball, tapering from the top of the root ball down to the surrounding soil grade. More root growth occurred in shrubs of the very difficult to transplant species mountain laurel planted with this technique than in those planted at-grade with PB amended backfill or at-grade with NOM (Wright et al., 2007).
The technique of Wright et al. (2007) attempts to simulate the organic litter layer found in natural environments, encouraging the initial proliferation of roots in this layer followed by proliferation in the upper soil horizons. As recommendations for using native plant species increase (Southeast Exotic Pest Plants Council, n.d.), it is possible that this planting technique could be used to successfully establish native shrubs in a variety of landscapes. The objective of this study was to determine the effect of planting technique, organic matter selection with above-grade planting, and planting season on post-transplant growth of two native landscape shrubs selected for their reportedly different landscape establishment success rates (Dirr, 1998).
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