Longleaf Pine Root System Development and Seedling Quality in Response to Copper Root Pruning and Cavity Size

Abstract Cultural practices that modify root system structure in the plug of container-grown seedlings have the potential to improve root system function after planting. Our objective was to assess how copper root pruning affects the quality and root system development of longleaf pine seedlings grown in three cavity sizes in a greenhouse. Copper root pruning increased seedling size, the allocation of root system dry weight to the taproot, and the fraction of fibrous root mass allocated to secondary lateral roots compared with primary lateral roots. It decreased the allocation of root system dry weight to primary lateral roots and led to a distribution of root growth potential that more closely resembled the root growth of naturally sown seedlings. These effects of copper root pruning may benefit longleaf pine establishment. However, because copper root pruning increased competition for cavity growing space among the taproot and fibrous roots, we suggest that recommendations regarding cavity size and seedling quality parameters be tailored for copper-coated cavities.