In the annual cycle of fruit trees, pruning periods can be divided into dormancy pruning and growth pruning. Dormancy pruning, that is, winter pruning; Pruning in growth period can be divided into spring pruning, summer pruning and autumn pruning.
(1) Winter pruning is dormant pruning. Refers to pruning under normal circumstances, from defoliation in winter to germination in the following spring. Before the normal defoliation of fruit trees in late autumn or early winter, the nutrients stored in the trees gradually changed from leaves to branches, from 1 annual branches to perennial branches, and from aboveground parts to underground roots. Therefore, the most suitable time for fruit tree pruning in winter is after the fruit tree completely enters normal dormancy, and the new shoots cut at this time contain the least nutrients, so the loss is the lightest. Pruning too early or too late will lose more reserve nutrients, especially weak trees, and more attention should be paid to choosing the right pruning time. In addition, some tree species, such as grapes, are pruned too late in spring, which is easy to cause bleeding and lose some nutrients. Although it will not cause the tree to die, it is easy to weaken the tree. Therefore, the most suitable pruning time for grapes is after defoliation in late autumn or early winter; However, when the walnut tree is pruned during dormancy, a lot of bleeding will occur and the tree will be weakened. Therefore, the suitable pruning time of walnut trees is spring and autumn, not winter. Spring is from walnut germination to flowering; Autumn is the peak period from walnut harvest to defoliation. In spring and autumn, autumn cutting is better than spring cutting. Pruning walnuts in autumn, the wound heals quickly and grows vigorously in the second year; Pruning after flowering in spring is easy to encounter fruit drop or hurt twigs.
The main function of fruit tree pruning in winter is to remove redundant branches such as dense branches, pests and diseases, concurrent branches and long branches, excessive flowering and weak branches, shorten the extension branches of main branches, auxiliary branches and fruiting branches, or renew fruit branches; Auxiliary branches, fruiting branches, or weak main branches that retract too much and too long; Incision stimulates branch buds in some parts and promotes the transformation to strong branches and strong buds; Adjust the angles and extension directions of main branches, auxiliary branches and fruiting branches.
(2) Spring pruning, also known as spring pruning, is the continuation and supplement of winter pruning. The pruning time in spring is from germination to flowering. Besides grapes, many fruit trees can be harvested in spring. When pruning in spring, measures such as thinning, cutting and girdling are often taken to ease the tree vigor, improve the germination ability of buds and promote the growth of short and medium branches. These measures are more suitable for tree species and varieties with few branches, vigorous growth and late fruiting; By thinning flower buds and adjusting the ratio of leaves to flowers, it is beneficial to high and stable yield of trees; Thinning or retracting excessive auxiliary branches or branches is beneficial to improve lighting conditions and increase the yield of high-quality fruits. However, after germination in spring, the nutrients stored in trees have been consumed by sprouting branches and buds. Once these branches and buds are cut off, the buds below will sprout again, which will consume more nutrients and delay growth. So the growth is obviously weakened. Therefore, spring pruning is mostly used for young trees and flourishing trees, which is not suitable for annual application. After cutting off the budding eyes at the top, it can promote the germination of buds near and below the incision, improve the germination rate and increase the amount of branches and leaves. In some years, when pruning in winter, the flower buds of some fruit trees are difficult to identify, and tree species prone to freezing injury can also be pruned after germination. However, the pruning amount in spring should not be too large, the number of branches cut should not be too much, and it should not be year after year, so as not to weaken the tree too much.
(3) Pruning in summer results in less nutrients stored in the tree, and some branches and leaves decrease after pruning in summer. Therefore, pruning in summer has a great inhibitory effect on the vegetative growth of trees, so the pruning amount should be light. Pruning in summer, as long as the time is right and the method is right, can adjust the balance between growth and fruit in time, promote the formation of flower buds and the growth and development of fruits; Making full use of secondary growth, adjusting or controlling crown is beneficial to the cultivation of fruit-bearing branches.
Summer pruning methods include pruning, pruning, twisting, girdling, carving, etc., which can be used flexibly according to specific conditions. Among young and flourishing trees, the effect of pruning in summer is more obvious.
(4) The pruning time in autumn is after the new shoots stop growing in the annual cycle and before entering the relative dormancy period. At this time, the tree began to store nutrients. Moderate pruning can make trees compact, improve lighting conditions, enrich branches and buds, and rejuvenate inner branches. After pruning in autumn, the wound reaction left by pruning in spring of the following year is weaker than that in winter, which is beneficial to inhibit the growth in vain. Autumn pruning, like summer pruning, is widely used in young trees and flourishing trees, and has obvious effect on controlling crown handover in dense planting gardens. Its inhibitory effect on vigorous growth is weaker than that of summer pruning, but stronger than that of winter pruning, and the tree vigor is not obviously weakened.
In short, the earlier pruning in the growth period, the more vigorous the secondary branches grow and the more flower buds are formed. Therefore, growing pruning has been widely used in production.