Influence of Container Design on Root Circling, Top Growth, and Post-Transplant Root Growth of Selected Landscape Species

Abstract

‘Delaware Valley White’ azalea, ‘Green Luster’ holly, ‘Plumosa Compacta Youngstown’ juniper, and ‘Shasta’ viburnum were grown for 1 to 2 years in four container designs: a conventional straight-walled round container, a square container with corner holes, a round container with stepped-pyramid profiles, and a poly bag. Poly bag, square, and stepped-pyramid containers significantly reduced root circling on all species compared to the traditional straight-walled round container. There were no significant differences in root circling among the three designs. Top growth was harvested at the end of 1 and 2 years. Effect of container design on top dry weight was species dependent. Poly bag, square, and stepped-pyramid containers increased top growth by 11 to 23% compared to the straight-walled round container. However, no one design was consistently superior for 2 years compared to the straightwalled round container. In addition, three of four species did not respond to container design l out of 2 years. Plants were transplanted into the landscape after growing for 1 or 2 years in the containers. After 16 weeks in the landscape, ‘Green Luster’ holly initially grown in poly bag, square, and stepped-pyramid containers had greater new root dry weight and smaller shoot (top):root ratios compared to the straight-walled round container. Top and new root dry weight of ‘Shasta’ viburnum were significantly affected by container design. However, the shoot:root ratios were not significantly different compared to the straight-walled round container. In the landscape, container design did not significantly affect top dry weight, new root dry weight or shoot:root ratio of ‘Plumosa Compacta Youngstown’ juniper.