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How to prune walnut trees and paper walnuts
Good tree shape and correct pruning of walnut trees are beneficial to skeleton formation, reasonable distribution of branches, solving the contradiction between growth and fruiting, and realizing early maturity, high yield, stable yield and high quality production.

1. Tree shape: Walnut trees with different tree potentials and different cultivation conditions should adopt different tree shapes.

Under the condition of close planting, the varieties with strong growth potential and upright tree posture, such as Xiangling, Liaohe No.4 and Luguang, are free spindles. Its tree shape is: the stem is 0.6m high, and there is a main branch on it every 30㎝ from bottom to top, which is spirally arranged. The tree is about 4m high, and there are about 10 branches on it. The angle of main branches is about 70 degrees, which should be smaller than that of apples. The fruiting branches are directly distributed on the main branches. This kind of tree has few branches and many fruiting parts, which is beneficial to early high yield and strong wind resistance. The shaping method is: after planting, the stem height is 80~90㎝, and there are 4~8 full buds under the incision. About five new shoots can be produced in the year of fixed stem, and the first new shoot will be cut as the central main branch from May to June, and the evenly distributed and vigorous side branches will be selected as the main branches. In the second year, 60㎝ short sections are reserved for the central extension branches, and 40-50㎝ short sections are reserved for other main branches, with an angle of about 60 degrees. When the length of the central extension branch is 60㎝, about 50㎝ should be left for coring to promote branching, and the main branch with good angle should be selected as the main branch, and the angle of pulling the main branch should be about 70 degrees in autumn. The pruning of the central trunk and main branches in the third to fourth years is the same as that in the second year, and other branches should be thinned if they are crowded; In this way, by the fourth year, the high energy of the tree reaches about 4 meters, and about 10 main branches are distributed on the central trunk, basically taking shape.

Due to poor drying, Yuanfeng and Lu Feng opened their trees in a delayed opening shape, with trunk height of about 60㎝, 5-6 main branches distributed on the trunk, and then fell down happily, with the central trunk height of about 2 meters and the tree height of about 3 meters. This kind of tree forms early and has good lighting conditions. Its shaping method: the stem height is 80㎝, the first vigorous branch under the incision is the central main stem, the central main stem is fixed with a big bamboo pole to make it grow upright, and the other 2-3 evenly distributed and vigorous lateral branches are the main branches. In the second year, the central extension branch is 60㎝ short and the main branch is 40㎝ short, and the angle of the main branch is pulled to 60 degrees. The main branch will continue to be selected on the central trunk. When the central extension branch is 60㎝, 40㎝ will be selected to promote the branch, and the new branch with good directionality will be selected as the side branch on the main branch. The third year of plastic surgery is the same as the second year. At the end of the third year, the height of the tree can reach about 3 meters, and 5-6 main branches can be selected on the central trunk.

2. Pruning period

Walnut branches have thick pith and much bleeding, so they should be pruned when the leaves fall in autumn and when they sprout in spring.

3. Basic methods of walnut pruning.

(1) Short-cut: Short-cut pruning method is widely used in improving walnuts, which is also the main aspect different from seedling walnut pruning method. Most of the female flower buds of the seedling walnut are born at the top of the fruiting mother branch, so the pruning method is sparse and long, less and shorter. More than 85% lateral buds of improved walnut 1 year-old strong branches can form female flower buds, blossom and bear fruit, and short cutting can prevent the fruit from moving out, enrich the base, and play the role of thinning flowers and improving fruit setting rate. The pruning reaction varies greatly with the pruning degree.

Heavy and short cutting: for 1 annual strong branch, about 2/3 of the branch length is cut off. Generally, strong branches of 1-2 can be produced under the cut, and the lower buds do not germinate or germinate into short and medium branches, and some of them die after germination, especially long white branches. This reaction is more obvious.

Light and short cutting: about 65,438+0/3 of the branch length is cut off, and 65,438+0-3 of the strong branches under the cutting mouth grow vigorously, and many short and medium branches grow under it. If the branches are stout, nutritious and robust, and the fruit setting rate is high, they can also bear good fruits. On the contrary, it is poverty. If you cut it too long, there will be many buds and branches, and there will be many fruits. However, if the growth potential is dispersed, the branches will easily weaken, and the basal branchlets will die and soon become bare, leading to the outward migration of the fruiting parts.

Medium and short cutting: about 1/2 branches are cut, and the reaction is between heavy cutting and light cutting. 2-3 strong branches can be produced under the cutting mouth, with vigorous growth and low fruit setting rate, and 3-4 branches with moderate growth potential can be drawn under it, with good effect, high fruit setting rate, full fruit core and forming in young trees. Branches at all levels can be pruned by short and medium cuttings.

(2) long-term release

Branches can be pulled out after long-term planting, but many branches are short and have not been pulled out. Only a small number of hair-prone branches are pulled out of the long branches, which is easy to cause baldness on the back and the resulting parts to move outward.

After long-term release, different varieties and branches have different reactions. For upright varieties and branches, only a few branches are pulled out from the branches, which grow vigorously, and there are no branches in the middle and back, which is easy to cause baldness in the back and the resulting parts to move outward; However, branches with wide tree posture and angle can germinate a large number of branches, with high fruit-setting rate and dense fruit-bearing parts.

(3) thinning

The compound leaves of walnut trees are relatively fat, so there shouldn't be too many branches left. The upright flourishing branches, cross branches, overlapping branches, over-dense branches, weak branches, male flower branches and the big branches behind them should be thinned in time to solve the ventilation and light transmission conditions in the inner room, so as to rejuvenate the fruiting branches and improve the fruiting ability. The upper part of erect varieties is prone to a large number of flourishing branches, which should be thinned in time. Otherwise it is easy to cause the lower branches to die. As a result, the website moved out.

(4) Shrinkage and shearing

Different degrees of retraction can rejuvenate the lower part, while the thickness of the retracted part and its branches has different rejuvenation effects. The retraction position is related to the position and growth intensity of the 1 branch under the incision. Generally, cutting 1 branch has a better rejuvenation effect when the growth is vigorous and the position is high, otherwise the effect is poor.

(5) Picking hearts in summer

From the second year, young walnut trees grow vigorously without topping, and the branch length can reach 1.5 ~ 2 meters. Picking in summer can promote branching, increase the number of branches, expand the crown as soon as possible, increase the number of fruiting mother branches, bear fruit early and yield high. For the vigorous branches with a length of about 60㎝, core is taken from the part above semi-lignification.

(6) branching

The shoots of walnut grow vigorously. In order to promote branching, branches can be pulled in late August and early September.

4 Pruning of fruit trees

From the initial stage of fruiting, it is necessary to cultivate strong fruiting branches in a planned way, increase fruiting parts, expand fruiting area and improve the yield of young trees. At the peak of fruiting, with the expansion of crown and the increase of fruiting parts, the contradiction between growth and fruiting is easy to appear. The pruning task in this period is mainly to adjust the relationship between vegetative growth and reproductive growth and improve the ventilation and light transmission conditions in the crown, so as to achieve the goal of high and stable yield. In pruning, it is mainly to balance the tree potential, slow down or cut off the strong branches, slow down their growth, increase the number of branches, and retract the renewed and rejuvenated fruit branches in time to prevent premature aging. Continue to cultivate fruiting branches, make good use of auxiliary branches and long branches in the inner cavity to prevent the hollow cavity of the crown and the fruiting part from migrating outward. Handle back branches, drooping branches and crowded branches in time to prevent tree crown.

(1) Trunk branch pruning: retract the crossed trunk branches in time, retract the excessively weak trunk branches to the obliquely growing side branches, and improve the angle of the extended branches. If the tree is about 3.5 meters high, it will drop its head in time.

(2) Cultivation of fruiting branches

Cultivating fruiting branches of walnut varieties is an important measure to increase yield, stabilize tree vigor, prolong fruiting year, prevent fruiting parts from moving out and prevent premature aging. There are three ways to cultivate fruiting branches:

First release and then shrink: that is, 1 year-old strong branches can generally produce new shoots of more than 10, and shrink in the second year to cultivate fruiting branches.

Cutting before releasing: When cultivating large fruiting branches in large space, the 1 year-old strong branches should be cut short first, and the previous 1 ~ 2 strong branches should be removed in the second year, and other branches should be released in order to cultivate fruiting branches. It is also possible to remove the core from the new shoots at the beginning of June to promote branching, and then retract them during winter shearing, and the fruiting branches can be cultivated at 1 year.

Transformation of auxiliary branches: after the auxiliary branches with space are completed, they can be cultivated into large branches by retraction method. Generally, the method of releasing first and then retracting is adopted, and the branch group position is better with anticlinal branches. Only twigs are left on the back, and no back branches are left. The branch spacing is controlled at about 60 ~ 80 ㎝.

(3) Pruning of fruiting branches

After the formation of fruiting branches, some medium-long fruiting mother branches should be pruned in different degrees every year to control the amount of fruit left, prevent the phenomenon of big and small years, and remove the over-dense branches, thin branches and some male branches in time. The pruning of the upright fruiting branches should not be too high, only 3 ~ 5 branches can be left, and it should be controlled within a certain range to prevent the main and lateral branches from expanding too much and affecting the growth. If the oblique branch group has a large space, more branches can be reserved appropriately to make full use of the space. The method of retraction and dewatering can be adopted in time to remove the lower branches and keep the upper branches, remove the weak branches and keep the strong branches, and renew the fruiting branches, so as to keep them growing and healthy all the time and prevent the bare lumen and fruiting parts from moving outward.

(4) Dorsal branch treatment

After a large number of walnut trees bear fruit, the growth of the upper branches on the back becomes weak, and the growth of the back branches becomes prosperous, forming the phenomenon of "backward pulling" of the main and lateral branches. If the opening angle of the original branch is small, the original branch can be cut off and replaced by the back branch. If the opening angle of the original branch is appropriate or large, the back branch should be retracted or thinned in time.

(5) Treatment of long branches

As a result, no long branches are usually left in the early stage, so as not to disturb the tree shape; In the full fruit stage, if there is space, select and keep it properly, and transform it into branches as soon as possible by cutting short and removing stones. But for a variety like Liaohe No.4, the upper branches should be drained in time.

(6) Secondary branch processing

Improved walnut is easy to form secondary branches. Because the secondary branches develop late, exuberant and not full, the basal branches have no buds for a long time and become bare, so they should be dealt with in time. When there is space, remove the weak and retain the strong, pick the core in June-July, control the vigorous growth, promote its formation of fruiting mother branches, and drain it in time when there is no space.

5 treatment of dense planting garden

After 3 ~ 4 years of planting, the crown began to close, and the pruning task changed from cultivating individual trees to managing the whole orchard. When the whole walnut orchard is closed and the outer crowns cross each other, the main branches of temporary trees (rows) should be retracted to control the crown to make way for permanent plants and ensure the normal growth of permanent plants. When temporary plants (rows) have no space to grow for 5 ~ 6 years, they should be removed in time.