ROOTSTOCK, SEVERITY OF DORMANT PRUNING, AND SUMMER PRUNING INFLUENCESON PEACH-TREE SIZE, YIELD, AND FRUIT-QUALITY

Peach trees in British Columbia are pruned heavily during the dormant season with some potentially detrimental effects. Summer pruning has b een used to control fruit tree vigor and improve fruit quality. The ob jective of this study was to reduce tree size, increase yield, and imp rove fruit color by using a less severe dormant pruning system and sum mer pruning prior to harvest. Over 4 yr, mature, self-rooted (micropro pagated) Fairhaven peach trees and Fairhaven on Siberian C rootstock w ere subjected to two different dormant pruning regimes, with or withou t summer pruning. Yield, tree growth, pruning weights (dormant and sum mer) and fruit quality (size and color) measurements were recorded ann ually. There were no differences in yields per tree for the two rootst ocks or for the summer pruning treatments. The lighter (''long'') dorm ant pruning increased yields but average fruit weight was higher in th e heavier (''short'') dormant pruning treatment. Summer pruning increa sed the amount of red color on the fruit but only slightly. Own-rooted trees were larger (tree height and ground area covered) than trees bu dded on Siberian C. Tree height was also increased by the lighter dorm ant pruning treatment. The partitioning index was higher for trees on Siberian C rootstock, ''long'' dormant pruned, or non- summer pruned t rees.