Modelling of pruning technique effects on branch architecture and subsequent year shoot flowering in hazelnut

Hazelnut crop yields are closely related to the number of flowers produced on a plant. The number of flowers borne by each plant is the product of the number of shoots and number of flowers borne on each shoot. Shoot flowering is correlated with shoot vigour. The aim of the present work was to test the hypothesis that pruning can be used in hazelnut to optimize the vigour of shoot populations on branches to increase branch flowering. Shoot growth, shoot flower density and shoot population size were measured in Tonda di Giffoni hazelnut plants trained to free bush in which branches were headed at different heights. Pruning increased shoot elongation and leaf appearance rates. Pruned branches had less shoots but of increasing vigor according to heading cut height. Shoot flowering was negatively correlated with shoot length. Female flowers were mainly induced in the buds borne on the first five basal nodes of shoots. Basal nodes were formed during the period when shoot growth was most intense. The data suggest that shoot growth competes with flower induction in hazelnut. Heading cuts affect branch architecture by stimulating growth of vigorous shoots that are less prone to flower and produce nuts in the next year. These results suggest that branch thinning is preferred over heading to maintain a branch architecture that are more favorable for flowering while increasing light penetration into the canopy.