Stock and scion investigations. XI. A twenty-year pruning and rootstock trial with apple trees

Abstract

Jonathan apple trees on 3 clonal rootstocks, M.XII, Essfour and Ivory’s Double Vigour, were pruned by 3 different systems from 1939 to 1959. Trees with unpruned leaders (Wickens system) grew larger in their early years than trees pruned to other systems. At 20 years of age, trunk girth was still greater than in trees subjected to hard or medium pruning. Total crop for the 20-year period was greatest in trees pruned to the Wickens system. Confirmatory results were obtained with the variety Granny Smith on Essfour rootstock. The smallest trees with the least amount of crop were Jonathan and Granny Smith on Ivory's Double Vigour rootstock. Differences in the weight of crop due to pruning systems could not be correlated with differences in trunk girth. An index based on crop, and trunk growth confirms the merits of trees pruned to the Wickens system. This index showed an increasing value with time.