1. dingan
Generally, in mountainous and hilly areas with shallow soil layer and poor soil quality, the fixed stem height is 40~60cm, and it can be slightly higher in gardens with thick soil layer and fertile soil such as flat land and gully, and the fixed stem of chestnut trees in dense planting gardens is lower than that in sparse planting gardens. When the stem is fixed, it should be cut off at the position where the bud is full and full within the height range of the stem. If the seedlings grow too fast, they should be fixed in the nursery by pinching in advance in summer, and then the branches should be promoted to grow and the main branches should be selected. If it is a seedling, it can be grafted in situ after planting, and can be combined with grafting to fix the stem.
Step 2: remove germination
In addition to the surviving branches and leaves, the new buds on the rootstock should also be erased in time to avoid competing for nutrients and water. For the trees that do not survive after grafting, all the sprouting branches will be removed except the vigorous sprouting branches with ideal branching angles and orientations on the rootstock, which will be replanted next year.
Pick a heart
Picking is mainly carried out on young trees and flourishing branches. In addition to normal winter pruning, summer pruning is an important technical link for early forming and flowering of chestnut. Generally, when the new shoots grow to about 20~30cm, the tender shoots with a shoot length of 3~5cm are removed, that is, the first coring. After enucleation, 3~5 buds at the top of new shoots germinate and grow again. When the length of the second and third new shoots is 50cm, the second and third coring are carried out, and the top length of the new shoots is 7~ 10cm. According to the local climate, the third and fourth coring should be carried out, and the new shoots formed should be strong and full, and should not be peeled in winter. When the secondary branches stop growing, the tender tips at the top should be cut off, which can obviously promote the formation of fruiting mother branches. Young trees should master the principle of early and light in the early stage and heavy in the late stage, and the new shoots formed after coring should be full and strong. After coring, several well-developed mixed buds can be formed at the top of the secondary or tertiary branches, which will bloom the next year. According to the survey, the proportion of mother branches bearing fruit after 2~4 times of branching is 35%~56%.
Pull branches
By pulling branches, bending branches, hanging branches and other measures, the angle of young branches is changed, and the strong branches are changed from upright to oblique, which inhibits the vegetative growth of strong branches, accelerates their transformation to reproductive growth and promotes the differentiation of female flowers. Branching can be carried out in autumn, the main branch angle should be 50 ~ 60, and the strong vegetative branch angle can be extended to 70 ~ 80 or even horizontal.
5. Selection and retention of extension branches of main branches
The pruning of main branch extension mainly involves the number, orientation, direction and pruning length of extension branches. Happy chestnut trees generally have 3~5 main branches. The main branches should keep a certain distance, and try to avoid the top 3~5 stout branches as the backbone branches at the same time. With the growth of the tree, the branches increase year by year, and the selection and retention of the main branches can be completed within 1~3 years. The selected main branches grow obliquely outward without overlapping and dispersion, which is beneficial to ventilation and light transmission. The selected main branch should be cut short at the full bud of the branch of 40~50cm to promote the branch of the main branch. Due to the tip advantage, the first bud under the incision produces a strong leading branch, which extends outward to expand the crown. When the angles of several flourishing branches at the top of the main branch are too small, the strong branches in the middle can be thinned out, and the slow branches with large angles of 2~3 buds at the top can be selected to replace the extended branches of the main branch. The selected extension branches of the main branches should be pruned every year until they reach the crown size required above.
6. Pruning of long branches and auxiliary branches
In the process of pruning young trees, because of the large amount of pruning, the hidden buds on the trunk often grow long branches. Tendrils that grow vigorously and erect, affect the main branches and disturb the tree shape should be removed in time. Tendrils growing in bare positions can be picked continuously in summer to promote branching and transform them into fruiting mother branches. The main function of auxiliary branches is to assist the growth of trees and should be transformed into fruiting branches as soon as possible. When pruning auxiliary branches, dense branches should be thinned out, and branches with room for development should be cut short.