The Fruiting Wall Orchard: Tree Training Results for Sweet Cherries, Nectarines, Apricots, and Plums

The evolution of stone fruit orchards from low density, stand-alone trees to high density, trellised tree walls has several driving forces: more uniform canopy light distribution, more uniform fruit development, labor efficiencies for thinning and harvest, potential mechanization of some pruning tasks, and better protective spray distribution, to name a few. Research trials on canopy architectural development and management have been carried out since 1999 on sweet cherry (Prunus avium L.), and since 2012 on nectarine (P. persica), apricot (P. armeniaca), and interspecific plum (P. salicina-based) hybrids. The most recent sweet cherry trial, part of the NC140 regional rootstock research project, examines the interaction of several canopy architectures, including Tall Spindle Axe (TSA), Upright Fruiting Offshoots (UFO), and Super Slender Axe (SSA), with precocious rootstocks that impart varying levels of vigor: dwarfing Gisela (Gi) 3, semi-dwarfing Gi 5, and semi-vigorous Gi 6. The other stone fruit species tend to be more naturally precocious than sweet cherry, but do not have comparably vigor-limiting rootstocks, thereby placing greater emphasis on canopy training to contain vigor within the fruiting wall framework. Depending on species, these stone fruits have been managed as TSA, UFO, SSA, or Palmate (PLM) canopies. Cumulative sweet cherry yields through Year 6, based on trial yields recalculated to suitable orchard tree spacing, were highest for TSA/Gi3, followed by UFO/Gi3 and UFO/Gi5. Although early yields were relatively high for SSA/Gi6, by Year 6 these had the lowest cumulative yield. Picking efficiency was 39% higher for the UFO fruiting wall canopies compared to the yield-comparable TSA trees. No significant differential trends in fruit quality have been detected yet. Fruiting wood renewal and maintenance of the fruiting wall structure will be discussed. For nectarines, the SSA canopies have best achieved vigor moderation, good yields, and good fruit quality. The spur bearing habits of the apricots and plums are well-suited for UFO canopy development and this architecture has moderated vigor relatively well. Summer hedging and topping are key components of canopy management across each of the stone fruit crops under study, with detailed hand-pruning in winter still required (though generally reduced by the mechanical hedging).