Gilman, E.F. and M. Orfanedes

Root pruning and planting depth impact root morphology in containers

Journal of Environmental Horticulture 30 (4): 173-181


Increasingly, producers and consumers are realizing that roots play a major role in nursery tree quality. To remain competitive, producers need to fi nd economically viable methods of increasing quality standards. Two studies were designed to test methods of improving root systems in a container root ball. In the fi rst, three different root pruning methods and two planting depths were imposed as 3.7 liter (1 gal) container-grown Royal poinciana [Delonix regia (Bojer) Raf.] and trumpet-tree [Tabebuia heterophylla (DC.) Britton] were shifted to 25 liter (6.6 gal) containers. Root pruning and planting depth had no impact on trunk caliper or tree height. Vertical root ball slicing or shaving off the periphery of the root ball increased the number of straight roots inside root balls and reduced the presence of defl ected roots, but shaving had a greater effect and was associated with consistently high-quality root systems. Trees planted with the top-most root 10 cm (4 in) below the 25 liter (6.6 gal) container substrate surface had more defl ected roots and fewer straight roots than trees planted with roots close to the surface. In the second study, teasing or shaving live oak (Quercus virginiana Mill. 'SNDL') in 3.7 liter (1 gal) container root balls resulted in identical root systems in 57 liter (15 gal) containers one year later, and both treatments resulted in higher quality root systems than trees not root pruned.

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