Positional influence on rooting of shoots forced from the main bole of swamp white oak and northern red oak

Abstract

The transition of ontogenetic maturity was assessed in two oak species by forcing softwood shoots from main bole stem sections in the greenhouse and from intact crowns, stumps, and hedged trees in situ and subsequently subjecting the new shoots to rooting trials. Mean shoot production was greater from forced stem sections of northern red oak (Quercus rubra L.) than from those of swamp white oak (Quercus bicolor Willd.) (14.6 and 4.6 shoots/m, respectively). Northern red oak stem sections exhibited a vertical gradient in the number of forced shoots; greater numbers originated from basal and juvenile sections of trees than from distal and mature sections. Rooting of swamp white oak shoots was low, 1.4% for forced shoots and none from hedged trees. Rooting of northern red oak was greater but variable, averaging 40.3% from greenhouse forced shoots and 0-35% from field-grown trees. Moreover, percent rooting was greatest for forced shoots originating from basal stem sections and declined with increasing distance from the tree base. The results suggest that ontogenetic maturation gradually increases, and rooting response decreases, along the bole of northern red oak trees.