Effect of nine rootstocks on growth and yield of two plum cultivars in a young orchard

A trial of two plum cultivars 'Queen Victoria' and 'Kubanskaja Kometa' grafted on 8 different clonal rootstocks: Ackermann, Brompton, G 5/22, Mariana GF 8-1, St.Julien A, St.Julien GF 655/2, Pixy, P. cerasifera 'Hamyra' and one P. cerasifera (local) was planted at the Polli Horticultural Institute in spring 2001. The objective of this trial was to assess the behaviour of the introduced plum rootstocks in Estonian conditions. In the fourth year from planting trees of both cultivars had the smallest trunk cross-section area on G 5/22 and Pixy rootstocks and the largest for 'Queen Victoria' on Brompton and for 'Kubanskaya Kometa' on Mariana GF 8-1 in autumn 2004. The late spring frost caused serious damage to flowers of both cultivars during flowering time in spring 2004. Flowers of 'Queen Victoria' were mostly killed, whereas flowers of 'Kubanskaja Kometa' were less damaged. Trees of 'Queen Victoria' produced only single fruits. The best average yield per tree was obtained from 'Kubanskaja Kometa' on Mariana GF 8-1. The average fruit weight of 'Kubanskaja Kometa' with St.Julien A was 49 g, which was significantly higher than the 41 g obtained with P. cerasifera.