The Effect of Root Pruning on the Root System of Nursery Trees

Abstract

Pruning root systems of landscape-size Colorado blue spruce [Picea pungens Engelm.) root systems in the nursery, 5 years before transplanting, increased the number of roots and the amount of root surface area in the root ball. The total root surface area of the harvest-ready 2m tall trees was increased from 122,000 cm2 to 245,000 cm2. The root ball of the root-pruned trees contained approximately four times as much root surface area as trees that were not rootpruned. Root balls of root-pruned trees contained 11.8 percent of the whole root system compared to 5.8 percent in root balls of unpruned root systems. Sixty percent of the pruned root systems were inside the dripline compared to 40 percent of the unpruned root systems. The increased absorbing root surface transplanted with the pruned trees should help to increase survival and reduce transplanting shock.