Two experiments were carried out with young apple trees (Fuji/Malus pruni folic Borkh. var. ringo) to examine the effect on the next season's shoot growth of summer and dormant thinning-out pruning, leaving short stubs. In Experiment 1 with 1-yearold trees, 4 lateral shoots which had been allowed to grow were cut, leaving 1.2 cm stubs on 8 occasions in the period between early July and late May in the next spring, while the terminal shoot was kept unpruned. The next season's shoot growth was weaker on the trees pruned in late August or earlier as compared with those pruned between late September and late March. In Experiment 2 with 2-year-old trees, which consisted of the central leader and 2 side branches, pruning was applied on 6 occasions in the period between late June and late November. All the shoots longer than 20 cm were cut, leaving 2-3 cm stubs except the terminal ones of the central leader and of two side branches. The next season's shoot growth was weaker on the trees pruned in late July or earlier than on the trees pruned between late August and late November. It was concluded that summer pruning does not invigorate the next season's shoot growth if it is applied early enough in the season for a balanced root : shoot ratio to be restored by the resultant regrowth.
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