Effect of Eight Container Types and Root Pruning During Nursery Production on Root Architecture of Acer rubrum

There is a general understanding that roots deflect when striking solid nursery container walls, and that on trees with good vitality this occurs within weeks of shifting into larger containers. Root architecture is poorly understood when observed in containers with walls constructed of porous plastic and of materials other than plastic. The objective of this study was to measure impacts of container type, root pruning when shifting to a larger container, and cardinal direction on root architecture in nursery containers up to the #45 size (approximately 170 L). Trunk diameter in #45 containers varied less than 5 mm among eight container types and was not impacted by root pruning. More root growth occurred in the northern than southern half of containers. Container type had a small impact on root architecture; in contrast, root pruning by shaving the periphery of the root ball at each shift had a large impact. Shaving when shifting dramatically reduced the percentage of trees graded as culls and suppressed stem-girdling root formation compared to not shaving. Shaving shifted deflected woody root mass from the interior of the root ball to the exterior, making it simple to remove peripheral roots when planting into the landscape.