Rootstock and Plant Spacing Influence Sweet Cherry Growth in Four Locations of Portugal

In March 2003, a trial was established at four sites in the main Portuguese sweet cherry (Prunus avium L.) producing areas to monitor 'Sweetheart' and 'Skeena' tree growth on three rootstocks (Edabriz, Gisela 5 [Gi.5] and 'MaxMa 14') and four in-row plant spacing. The between-row distance was 5.5 m and in-row distances were 70, 140, 210 and 280 cm, corresponding to approximate densities of 2600, 1300, 860 and 650 trees/ha. Trunk diameter was measured at the end of the 2(nd) leaf, and ANOVAs were conducted on the values for trunk cross-sectional area (TCSA). Significant growth differences were detected for rootstock, location and plant spacing. The rootstock was the factor that influenced plant growth the most in all locations; the trees on 'MaxMa 14' had a TCSA of 21 CM, whereas those on 'Edabriz' and Gi.5 were only 59 and 45%, respectively, of the MaxMa value. The trees at Caria grew 7, 31 and 43% more than those at C. Montenegro, Vila Real and Alcongosta, respectively. 'Edabriz' reduced TCSA between 35% in Carrazedo de Montenegro and 46% in Caria, while Gi.5 reduced growth to 52% in Alcongosta and 60% in Caria. Trees at the highest density (2600/ha) had the greatest TCSA reduction (17%). Overall, TCSA consistently decreased with closer in-row tree spacing; the decrease was 24, 21 and 16% on 'MaxMa 141, Gi.5 and 'Edabriz', respectively. In summary, density affected growth reduction the most in trees planted at 70 cm because of the greater competition, mainly on the semi-dwarfing rootstock.