TIMING AND SEVERITY OF SUMMER PRUNING AFFECTS FLOWER INITIATION AND SHOOT REGROWTH IN SWEET CHERRY

To examine the effect of timing and severity of summer pruning on flow er bud initiation and vegetative growth, 4-year-old 'Bing' cherry tree s (Prunus avium L.) were pruned at 31, 34, 37, 38, or 45 days after fu ll bloom (DAFB) with heading cuts 20 cm from the base of current-seaso n lateral shoot growth, or at 38 DAFB by heading current-season latera l shoot growth at 15, 20, 25, or 30 cm from the base of the shoot. The influence of heading cut position between nodes also was examined by cutting at a point (approximate to 20 cm from the shoot base) just abo ve or below a node, or in the middle of an internode. Summer pruning i nfluenced the number of both flower buds and lateral shoots subsequent ly formed on the shoots. All of the timings and pruning lengths signif icantly increased the number of both flower buds and lateral shoots, b ut differences between pruning times were not significant. There was s ignificantly less regrowth when shoots were pruned just below a node o r in the center of an internode, rather than just above a node, sugges ting that the length of the remaining stub may inhibit regrowth somewh at. The coefficient of determination (r(2)) between flower bud number and regrowth ranged from -0.34 to -0.45. In young high-density sweet c herry plantings, summer pruning may be useful for increasing flower bu d formation on current-season shoots. The time of pruning, length of t he shoots after pruning, and location of the pruning cut can influence subsequent flower bud formation and vegetative regrowth.