Year-by-year pruning method for the open-center tree form

The purpose of pruning the open-center tree form from year 6 to year 7 is to expand the canopy and develop lateral branches. On each primary branch, at intervals of about 60 cm, first retain 2 vigorous secondary shoots with a narrow angle as the first and second lateral branches. To ensure the growth advantage of the lateral branches, all secondary shoots other than the primary branch leader and the lateral branches are headed back. During the growing season, apart from the extension growth of the primary and lateral branches, the vegetative shoots that sprout on other parts are pinched in time to control their growth, so as to achieve a clear hierarchy of main and subordinate branches and to ensure the third lateral branch. In this way, after about 15 years the open-center tree form is formed.