Converting Tall Spindle Apple Trees to Narrow Walls with Summer and Dormant Hedging Plus Root Pruning

Abstract

Recently, some commercial apple growers have been adopting hedging as an alternative or supplement to hand-pruning. With increasing labor costs across the United States, alternatives to hand-pruning and current training systems are being considered. One management strategy involves transitioning tall spindle trees to a narrow tree wall and simplifying labor-intensive activities of apple production, such as pruning, harvesting, and fruit thinning. The objective is to form the orchard system into a “fruiting wall” that makes fruit more visible and accessible, thus facilitating harvesting. Four management practices (tall spindle; narrow tree wall with manual pruning; narrow tree wall with dormant and summer hedging; and narrow tree wall with dormant hedging, summer hedging, and root pruning) were used to convert 12-year-old ‘Brak Fuji’ apple trees from the tall spindle training system to a narrow tree wall. Photosynthetically active radiation (PAR) and ultraviolet light levels within the canopies were improved by summer hedging, but they were still low for all treatments. Light within the canopy was improved most when root pruning was included. Specific leaf weight was not significantly impacted by hedging or root pruning. Detailed spur sampling showed that treatments had no effect on vegetative or reproductive growth on 2- to 3-year-old wood. Although dormant plus summer hedging alone did not affect shoot length, the combination of hedging and root pruning caused a significant reduction in terminal shoot length. Red fruit color was only improved with dormant hedging plus summer hedging plus root pruning. Compared with dormant plus summer hedging, dormant plus summer hedging plus root pruning improved fruit set and yield, but it reduced fruit size. Without root pruning, hedging had little effect on light, specific leaf weight, flower initiation, fruit set, and fruit quality. Conversion to narrow tree walls by manual pruning resulted in more poorly colored fruit and less highly colored fruit compared with maintaining the trees as tall spindles with manual pruning.