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Sample root pruning protocol for nursery production
This protocol resulted in a compact root system that transplanted live oak trees with 100% survival:
Spade root pruning was accomplished by slicing a square tipped balling shovel 36 cm (14 in) long into the soil at an angle similar to that of a mechanical tree spade. North and South one-eight circumference segments (12.5 percent of circumference each, totaling 25% circumference) were pruned in April 1999 20 cm (8 in) from the trunk and East and West one-eight segments were root pruned in May. Root pruning was repeated in August (NW and SE segments) and September (NE and SW segments) 27 cm (11 in) from the trunk. The bottom of the hand spade did not reach far enough into the soil to overlap adjacent slices so any roots growing directly down under the trunk were not cut.
Many nurseries that root prune field nursery stock now do so with a tree spade. Many of these growers sink blades about half way into soil essentially cutting half the root system. Later in the year, the other half is cut with the spade.Our most recent (not published yet) showed that for live oak, the time of year trees were root pruned did not impact growth in the nursery nor water stress following digging.
