The Response of 'Montmorency' Tart Cherry to Renewal Pruning Strategies in a High Density System

Tart cherry (Prunus cerasus) production in the U.S. is based on low-density plantings designed to accommodate large trunk-shake mechanical harvesters. Availability of canopy-shake harvesters adapted to smaller trees could facilitate transitioning to high-density (HD) precocious systems, based on continuous fruiting walls that are highly efficient at light capture. HD systems would require specialized pruning techniques to maintain long-term productivity while maximizing the efficiency of a limited labor supply. Experimental HD orchards with multiple rootstocks, training systems and tree densities were used for investigating renewal pruning strategies. Pruning cuts of predetermined lengths ranging from 0 cm to 25 cm were made on branches of differing size (0.6 cm to 4.7 cm diameter), and renewal growth was monitored for shoot number and length. The minimum stub length for generating at least one renewal shoot was approximately 10 cm. However, this differed somewhat with rootstock and diameter of the cut branch, where the critical length was shorter for larger diameter branches and on the more vigorous rootstock. Results provide guidelines on pruning of HD plantings to renew fruiting wood and maintain productivity.