Integration of Renewable Canopy Architectures and Precocious Rootstocks Optimize Sweet Cherry Yields, Fruit Quality, and Labor Efficiency

Sweet cherry (Prunus avium L.) production systems have been evolving since the commercial advent of precocious and dwarfing rootstocks in the 1990s.  A multi-institutional coordinated regional research trial (NC140 project) was planted at 13 locations across North America in 2010 to study the impact of precocious rootstocks of varying vigor levels on development of four different canopy architectures, their management, and performance in terms of productivity and fruit quality. The trial at Michigan State University utilized ‘Benton’ on dwarfing Gisela (Gi) 3, semi-dwarfing Gi 5, and semi-vigorous Gi 6 rootstocks. The canopy architectures include 1) a multiple leader bush with vertically-oriented fruiting units having primarily spur-fruiting sites (aka Kym Green Bush, KGB); 2) a spindle/central leader tree with lateral fruiting units having both spur- and non-spur fruiting sites (aka Tall Spindle Axe, TSA); 3) a trellised fruiting wall comprised of an oblique-horizontal cordon-leader with vertically-oriented fruiting units having primarily spur-fruiting sites (aka Upright Fruiting Offshoots, UFO); and 4) a fruiting wall comprised of very closely-planted single leader trees with very short lateral fruiting units having primarily non-spur fruiting sites (aka Super Slender Axe, SSA). Across all canopy architectures, trees on Gi3 were most precocious and productive through Year 4; in Year 5, trees on Gi5 generally achieved similar productivity as those on Gi3. Across all rootstocks, SSA trees were most precocious and productive through Year 4, but in Year 5 yields declined, with UFO and TSA trees becoming most productive. These changing yield trends, as trees completed establishment and filling of allotted orchard space through maturation and renewal of canopy fruiting units, relate somewhat to the inherent differences (due to canopy training and management) in fruiting populations (spur vs. non-spur fruit clusters), which will be discussed. In Year 5, the most yield-efficient "fruiting wall" architecture was UFO and the most yield-efficient “three-dimensional” architecture was TSA. All canopy architectures except KGB have the potential for partial mechanization by summer hedging to reduce pruning costs. Differences in timing of hedging on re-growth, flower formation, and summer–winter pruning labor efficiency were quantified in 2014–2015 and also will be discussed, along with yields for Year 6 (2015).