Influence of Backfill Soil Amendments on Establishment of Container-grown Shrubs

Abstract

Cotoneaster apiculata and Juniperus chinensis `Pfitzeriana Compacta' were planted on a site with compacted clay soil. Plants were placed in holes the same size as the root ball (no backfill), or in holes three times the diameter of the root ball with sloping sides. The three backfill soils used were composed of site-soil (50%) amended with sand (40%) and leaf compost (10%), site-soil (75%) amended with mushroom compost (25%), and unamended site-soil. After 14 months, root density was not different in any of the treatments, and root densities were not different in the compacted clay soil outside of the planting hole, indicating that root growth was not inhibited at the interface between the backfill soil and the compacted site clay soil. Shoot growth of C. apiculata grown in backfill amended with sand and leaf compost was larger than shoot growth of plants grown in other backfills.