Developments in high density cherries in France: Integration of tree architecture and manipulation

Over the last 10 to 15 years in France, there has been an increasing interest in: (1) growing precocious sweet cherry trees to increase early economic returns; (2) increasing marketable yield of well-colored, high-quality fruits; and (3) reducing orchard labor costs, notably those relating to pruning and harvest. The use of semidwarfing (e.g., Maxma Delbard((R)) 14 Brokforest) or dwarfing (e.g., Tabel((R)) Edabriz, Gisela 5) rootstocks is now widespread in young French orchards and makes it possible to adequately control canopy height and volume, as well as precocity. High-density tree forms belong to two groups: (1) vase-shaped trees with 5 to 6 scaffolds per tree and 600 trees/ha (i.e., 3,000 to 3,600 scaffolds/ha), and (2) central leader-shaped trees, e.g, Tatura trellis, Vertical Axis and a combination of both called Taturaxe, with 1000 to 1500 trees/ha at planting densities of 4.5 to 5 m x 1.5 to 2 m. The Vertical Axis system has evolved into the Solaxe training system, with bending of the distal part of the trunk at the desired height (2.5 to 3.5 m), and bending of the lateral fruiting branches when necessary. Renewal pruning was abandoned in favor of the thinning-out of spurs. This procedure is called "spur extinction" or "extinction". For 6 years, experiments have been carried out at INRA, France, at experimental stations and in commercial orchards, to assess the technical feasibility and economic interest regarding this training tool. Extinction has proven to have a more interesting effect on crop load and individual fruit size than conventional renewal pruning on various cultivars, such as 'Summit', with a persistent effect in the year following treatment. As a general trend, the spacing between spurs brought about by spur thinning leads to an increase in fruit size and color and a decrease in brown rot incidence. On-going experiments focus on adapting extinction procedures to an overall tree training program across cultivars.