Container Production Strategies Influence Root Ball Morphology

Abstract

Poor anchorage and delayed establishment have been associated with root circling and ascending, descending, and kinked roots occurring in nursery containers. The main goal of this study was to find methods of producing from seed Swietenia mahagoni (L.) Jacq. with straight, non-deformed roots. In contrast to smooth-sided (SM) propagation containers (liners), roots grown in pots constructed of thin paper were straight with few deflections. Root pruning 12-month-old SM liners when shifting to 3.8 L containers dramatically reduced the imprint on the root system left by root deflections. Aggressive growth at the bottom of 3.8 L and 9.5 L smooth-sided containers appeared to inhibit growth in horizontal roots closer to the substrate surface, and resulted in a vertically oriented root system. In contrast, growing trees in 3.8 L and 9.5 L containers with exceptionally porous walls produced a more horizontal-oriented root system similar to well-anchored trees in the landscape. Vertical roots were discouraged from developing due to an elevated and porous bottom, forcing roots to grow more horizontally higher in the root ball profile. Root deflections increased with retention time in all containers.