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Effect on Growth of Young Trees 



Pruning while the shoots are still elongating tends to cause 

 new shoots to start growth from the axillary buds below the pruning 

 cuts. The amount of regrowth may show little correlation with 

 severity of pruning. We have foiond that Red Prince Delicious pro- 

 duces more of this regrowth than Cortland. Tree vigor at time of 

 pruning also is an important variable since the length of shoots 

 at time of pruning is highly correlated with amount of regrowth, 

 i.e., the longer the shoot, the greater the regrowth. 



Pinching did not devitalize the trees in our studies, whereas 

 heading restricted the size of vigorous trees. Considerable regrowth 

 follows summer pruning of vigorous young trees in late-June through 

 mid- July. However, if substantial leaf surface is removed at this 

 time, regrowth does not compensate for the removed surface. July 

 and early-August appear feasible times for restricting tree size by 

 summer pruning, but regrowth may be less when pruning is done in 

 early-August . 



Pinching and heading cuts on vigorous Red Prince Delicious 

 trees in early or mid-July frequently causes new shoots to start 

 growth from 2 or more of the axillary buds below the pruning cuts. 

 Thus, a proliferation of growing points occurs just as when trees 

 are sheared with mechanical pruning devices during dormant season. 



Whether the proliferation of growing points can be considered 

 an unfavorable response in all cases remains to be proven. However, 

 clearly unfavorable responses to summer pruning have occurred. On 

 Cortland/7A trees, 181 of the shoots headed on July 18, 1976 were 

 dead in 1977; death of headed shoots occurred less frequently follow- 

 ing the July 1 and August 2 pruning dates. Many current season's 

 shoots on Cortland/7A and Red Prince Delicious/26 stubbed in 1977 

 failed to produce regrowth. In 1978, 71% and 50% of the stubs were 

 dead on the Cortland and Red Prince Delicious, respectively. Some 

 flowering from axillary flower buds and spurs has occurred in Sept- 

 ember of the year of pruning. Summer-pruned trees also have shown 

 a tendency to mature their wood later in the fall as evidenced by 

 delayed leaf abscission, and this may lead to winter injury. Fur- 

 thermore, Starkrimson trees that had been summer pruned by heading 

 cuts in 1976 made more growth than the control trees in 1977; thus, 

 the advantages of vegetative growth control in 1976 were lost in 

 1977 without follow-up summer pruning. 



E ffect on Formation of Flowering Spurs 



We wanted to determine if stubbing, heading, or pinching current 

 season's shoots in summer caused a flower bud to form immediately 

 below the cut. Stubbing is preferred in some fruit growing areas 

 because less regrowth is produced and thereby more chance for ini- 

 tiating flower buds than when a longer stub is left as with heading 



