Timothy M. Spann

Neoformed growth responses to dormant pruning in mature and immature pistachio trees grown on different rootstocks

Summary The relationship between pruning and the production of neoformed growth in ‘Kerman’ pistachio (Pistacia vera L.) trees on different rootstocks was investigated to determine if the increased neoformed growth common in trees on more vigourous rootstocks was related solely to rootstock vigour, or was an artifact of pruning practices. While some neoformed growth was inherent in mature trees, pruning increased the amount produced on each tree regardless of rootstock or crop load. However, regardless of pruning severity, the least vigourous rootstock never produced as much neoformed growth as the two more vigourous rootstocks. Pruning cuts made into 2-year-old wood were the most stimulatory, while pruning cuts into 1-year-old wood resulted in growth similar to unpruned controls. The data presented indicate that the invigorating response to pruning in young trees is highly localised, and that pruning can be varied depending on the stage of tree development and the desired growth response. Overall, the data suggest that hand-pruning, while more costly in the short-term than mechanical pruning, may be useful in creating a more desirable canopy architecture, thereby potentially reducing long-term pruning needs and overall management costs.