CANOPY MANAGEMENT PRACTICES IN MODERN PLUM (PRUNUS DOMESTICA L.) PRODUCTION ON VIGOROUS ROOTSTOCKS

Intensive high-density plantings (HDP) of plum trees in the Republika Srpska involve the use of Myrobalan (Prunus cerasifera Ehrh.) seedling as the predominant and, in most cases, the only rootstock. Using Myrobalan as a vigorous rootstock is a serious challenge in growing plums at higher planting densities. Although Myrobalan seedling rootstock increases the vigour of grafted cultivars, plum trees trained to the spindle system on Myrobalan rootstock can also be grown at very high plant densities ranging from 1,000 to 1,800 trees per hectare, depending on the cultivar/rootstock combination and central-leader inclination. The most common training system for plums in high density plantings is the slender spindle or the spindle bush system. Successful training and maintenance of spindle systems in intensive production on high-vigour rootstocks is not possible without the consistent use of canopy management practices, particularly during the first three years after planting, when these practices are most intensive for proper training of both the central leader and main lateral branches. Canopy management practices require a professional attitude and substantial manual labour. Particular importance in training spindle systems for plums as well as in maintaining the training system (replacement of spur-bearing branches) is given to the following specific canopy management practices: notching, shoot bending, shoot twisting, undercutting and replacement of spur-bearing branches. This paper outlines some important canopy management practices and their effect on plum growth and development, focusing on cultivar-specific responses to treatments.