Pruning characteristics of walnut trees at different ages

   1. The pruning period of walnut is different from that of other fruit trees. Because the dormant pruning of walnut after defoliation will cause "wound flow" by the wound, resulting in nutrient loss, tree weakness, and even branch death, it is not suitable to be carried out in winter. The bleeding period of walnut is generally from falling leaves in autumn to before sprouting in the following year (that is, from mid-November to late March). For this reason, walnut pruning should avoid the bleeding period. The period of suitable pruning should be from the harvest of the fruit to before the leaves turn yellow and after the leaves are unfolded in spring. However, spring shearing loses a lot of nutrition, and it is easy to hurt tender branches and leaves, so it is appropriate for adult trees to be cut in autumn before October when the leaves do not turn yellow after fruit picking. Young trees can be pruned in spring, summer and autumn. In recent years, it has also been pruned during the low ebb period between the two peaks (from mid-December to mid-March), and no or only minor injuries have occurred. The response after winter pruning is better than spring pruning and autumn pruning, so many experts advocate winter pruning, and the best pruning time is before spring sprouting.

   2. The shaping and pruning walnut of young trees grows very fast in the young tree stage. If it is allowed to develop freely, it is not easy to form a good high-yield tree shape, especially the early-bearing walnut, which has strong branching power, early fruit, easy to produce secondary branches and cause tree shape disorder, which is not conducive to normal growth and fruit. The task of pruning at the young tree stage is to cultivate a strong skeleton and a high-yielding tree. Attention should be paid to adjusting the subordinate relationship of branches at all levels so as to maintain the advantage of the central stem and the robust growth of the main branches. The central stem uses the terminal bud branch as an extended branch, and more auxiliary branches are left on it to strengthen the growth of the central stem. The competition branch and the back branch should be controlled on the main branch.

There are usually two types of    walnut shaping: sparse layer shape and natural happy shape, which can be adapted to local conditions according to the characteristics of varieties, soil quality, fertilizer management and so on.

   (1) has obvious central trunk, 5-7 main branches, large crown and high yield. It is suitable for walnut trees with strong upright varieties, rich and deep soil and good cultivation and management conditions.

   (2) is naturally happy without central stem, less main branches and small crown, so it is suitable for walnut trees with open crown, poor soil or poor management conditions. According to the number of main branches, there are three kinds of happy branches: two main branches, three main techniques and multiple main branches.

   3. Fruit tree pruning walnut tree enters the fruiting period, the crown continues to expand, the fruiting position continues to increase, and it is easy to appear the contradiction between growth and fruit. ensuring high and stable yield of walnut is the main task in this period. Therefore, in pruning, we should always pay attention to the cultivation of good branch groups, using auxiliary branches and overgrown branches to deal with the back branches and drooping branches in time.

From the early fruiting stage,    planned to cultivate strong fruiting branch groups, increase fruiting parts, expand fruiting area, and increase the yield of young trees. In the peak fruiting period, with the expansion of the crown and the increase of the fruiting position, it is easy to appear the contradiction between growth and fruit. the main task of pruning in this period is to adjust the relationship between vegetative growth and reproductive growth and improve the ventilation and light transmission conditions in the crown. in order to achieve the purpose of high and stable yield. In pruning, it is mainly to balance the tree potential, slowly release or cut short strong branches, ease its growth, increase the number of branches, retract and renew the rejuvenated branches in time, and prevent premature senility. Continue to cultivate the fruiting branch group, make good use of the auxiliary branch and the inner chamber growing branch to prevent the inner chamber of the crown from being empty and the fruiting part from moving outward. Timely treatment of back branches, drooping branches, dense squeezed branches to prevent closeness.

   (1) pruning of early fruiting trees during this period, the tree structure is initially formed. The tree potential should be balanced, the upright and upright branches should be removed, the peripheral dense branches and ineffective Internode branches should be removed, sufficient effective branches should be retained (thick, short, strong), strong branches should be controlled to develop slowly (take, pull and change heads in summer), and all available fruit branches (including drooping branches) should be fully utilized. To achieve the goal of early fruit and early high yield.

   (2) Walnut trees in the pruning and fruiting stage, most of the canopy is close or already closed, the number of outer branches increases gradually, and most of them become fruiting branches, and some of the branchlets are dry and bald zone appears at the back of the main branch due to lack of light. Results when the site moved outward, it was easy to result in the next year. Therefore, the main task of pruning at this time is to adjust and improve the ventilation and light transmission conditions in the crown and constantly renew the fruiting branches in order to achieve the purpose of high and stable yield. The main points of pruning are as follows: thinning diseased branches, penetrating sunlight, shrinking periphery, promoting inner chamber, raising angle, saving nutrition, branch group, and increasing yield.

   4. After the pruning walnut of senescent trees enters the aging period, the shoots and big branches often die, and the yield decreases year by year, so it should be renewed and rejuvenated in time to prolong the fruiting years.

   (1) Trunk Renewal (Great Renewal) saws off all the main branches to make them re-branch and form the main branch.

For the plants whose trunk is too high,   ① can saw off all the crown in the appropriate part of the trunk so that the latent buds under the saw can sprout new branches, and then select 2 or 4 branches with suitable direction and strong growth from the new branches to culture into main branches.

  ② trunk is a highly suitable happy-shaped plant that can be sawed off at the base of each trunk. If it is a trunk-shaped plant, the crown can be sawed off from the upper part of the first main branch, and then sawed off from the base of each main branch, so that the latent buds at the base of the main branch can sprout.

   (2) the main branch renewal (moderate renewal) retracts in the appropriate part of the main branch to form a new side branch. the specific pruning method is as follows: select the robust main branch, retain the length of 50 ~ 100cm, and cut off the rest to make it branch near the saw mouth of the main branch. after branching, 2 or 3 strong branches with suitable orientation are selected on each main branch and cultured into a first-class lateral branch.

   (3) lateral branch regeneration (minor regeneration) retracts the primary lateral branch in the appropriate position to form a new secondary lateral branch. Its advantage is that the formation of new crown and the increase of yield are rapid.