SUMMER PRUNING YOUNG SWEETHEART SWEET CHERRY TREES AFFECTS YIELD AND TREE SIZE

'Sweetheart' sweet cherry trees (Prunus avium L.) were summer-pruned f or four summers (1991-94) either before or after harvest and at two le vels, removing 1/3 or 2/3 of current-season growth by heading cuts. In an additional postharvest treatment, some current-season growth was r emoved by thinning cuts. The preharvest 1/3 treatment had the highest cumulative yield during the experiment. Higher yields were obtained fo llowing preharvest than postharvest treatments, and following less sev ere treatments (removing 1/3 of current-season growth) than more sever e (removing 2/3) treatments. These increased yields were for the early stages of orchard production. Average fruit mass was not affected by any of the treatments. The summer-pruned trees had smaller trunk cross -sectional area (TCSA) increments over the trial and their final TCSA was smaller than that of the control trees.