Influence of Different Training Systems on the Beginning of Domestic Plum Production and Yield

All growers prefer to obtain a first harvest as soon as possible. The aim of this study was to identify an effective tree training system for new Latvian plum cultivars, which provides the highest yield and fruit quality. The trial was established in 2012 at the Institute of Horticulture (formerly Latvia State Institute of Fruit-Growing) and included cultivars ‘Ance’, ‘Adelyn’, and ‘Sonora’; and the controls ‘Victoria’ and ‘Jubileum’. Planting distances were 4 × 2.5 m, and the rootstock was Prunus cerasifera. Tree training was done using four systems: two systems with branch bending (Heka espalier and spindle); and two systems without bending (standard (round) and flat crown). Evaluation of average fruit weight and yield per trunk cross section area (TCSA) was done from 2015 to 2017. The Heka espalier and spindle systems had first yield in 2015, but systems without bending had first yield only in 2016. Average yield per TCSA was significantly higher for the Heka espalier system (0.49 kg·cm⁻²) than for the spindle system (0.24 kg·cm⁻²), standard crown system (0.17 kg·cm⁻²), and flat crown system (0.30 kg·cm⁻²). Cultivar ‘Victoria’ had the highest yield among all systems. Average fruit size showed the same results: the biggest fruits were obtained with the Heka espalier system, and the smallest for systems without bending in the standard crown.