After persimmon enters the senescence stage, the shoots and lateral branches are dying, the crown is gradually shrinking, the growth is also very weak, and the nudity in the crown is becoming more and more serious. The top of the tree is burnt, and the annual growth is very small. As a result, the position moves outward, the main branches are incomplete, the yield drops rapidly, and the back branches are clustered, showing a natural regeneration phenomenon; The fruiting ability of branchlets is weakened, and the phenomenon of fruiting every other year is serious.
The task of old tree regeneration and pruning is mainly to renew and re-form its crown. The principle of pruning is: the upper branches fall off and contract again; The lower branch is slightly retracted; Severe retraction of severe aging and appropriate retraction of mild aging. When pruning, the degree of retraction should be determined according to the aging of the tree. For the branches with bare base and slender drooping, they can be retracted in the place with good branches or long branches, which is usually about 5-7 years, so that the new branches can extend forward instead of the original big branches, maintain appropriate fruiting parts and maintain a certain yield.
When recovering the big branches, we should grasp them flexibly according to the actual situation. A branch will shrink when it ages, and so will the whole tree when it ages. Don't retract too much to avoid too many branches. New branches and long branches sprouting on the crown can be pruned in summer and cultivated and utilized in time; Those left as new backbone branches should be picked properly, pulled out in time and opened obliquely to promote expansion and extension; Too dense branches should be drained in time, and pruning measures such as coring should be taken in time to cultivate them into bearing branches.
For long branches, it is necessary to control the pinching in time to prevent baldness at the back, otherwise it is difficult for such branches to bloom and the yield will recover slowly. Too much retraction, too many wounds, difficult to heal, and easy to cause xylem rot.
Excessive growth of branches in old trees is a good branch to restore the crown, which should be protected and utilized, and can be picked in time to promote the growth of branches, form new backbone branches, update the crown or cultivate fruit branches; For the small regenerated branches in the inner cavity of old trees, the branches that are too dense and too thin can be thinned, and the remaining branches can be picked in time to promote their strength and cultivate them into fruiting branches so as to restore the yield as soon as possible.
High grafting refers to grafting by perennial seedlings or by changing improved varieties. The original balance between the aboveground and underground parts of this grafted tree was broken due to the sudden narrowing of the crown. In order to restore its original balance, after survival, the grafted aboveground branches grew vigorously, with strong branching ability, thick branches and large leaves, long growth period and stopped growing in the later stage. Pruning of such trees should be carried out immediately after grafting and branching survive. When the new shoots grow to a certain length, they should be picked in time and repeatedly, so as to form a good tree skeleton and bear fruit as soon as possible. For those redundant and dense branches, they should be thinned as soon as possible to avoid consuming nutrition.
Generally, two or more scions are often inserted when high grafting is carried out on branches with a thickness of 4 ~ 5 cm. After survival, the buds on each scion can germinate into branches, so it is easy to cluster. When the length of new branches is about 10 cm, according to the requirements of plastic surgery, stout new branches with suitable direction and angle should be selected as backbone branches, other new branches should be thinned and the rest should be pitted to maintain the growth advantage of backbone branches. If it is not suitable to keep the upper new shoot as the backbone branch, the backbone branch should be selected from the lower part, and the upper new shoot should be cut off to maintain the top advantage of the selected new shoot. If two scions grafted in the same position sprout new buds at the same time, only 1 new bud is needed, and other new buds should not be thinned temporarily, so as not to affect the survival of the preserved new buds or make the interface not heal and rot. However, in order not to make two new shoots compete, it is necessary to pick another new shoot in time to promote growth and branching, and then cultivate it into a fruiting branch group.
When the new shoots of grafted trees grow to a certain length, the core is removed according to the requirements of shaping to promote growth and branching; For other new shoots that have been picked, if they germinate for two or three times, some of them can be properly thinned, and the rest can be picked again to increase the number of branches and cultivate them into fruiting branches. However, the height of these new branches cannot exceed the new branches reserved as main branches.
When pruning in winter, the dense, crossed branches and new branches sprouted on the rootstock should be thinned according to the requirements of shaping, so as to maintain vigorous growth, rapidly expand the crown, increase the fruiting parts and increase the yield as soon as possible.