In the park green space, proper pruning and shaping of garden trees is a very important conservation and management technology. Pruning and shaping can adjust the tree potential, create and maintain a reasonable crown structure, form a beautiful tree posture, and even form a landscape with certain characteristics. ? In urban street greening, because of the relationship between underground cables and pipelines, the contradiction between them and trees is usually solved by pruning and shaping measures. In areas invaded by typhoons, pruning and shaping measures can reduce wind damage and prevent lodging. For prolific tree species, such as trees, mulberry trees, tea trees and wood, pruning and shaping measures can promote high yield and high quality. ? "Pruning" refers to the measures to cut off or cut off some organs of plants, such as stems, branches, leaves, flowers, fruits, buds and roots. "Shaping" refers to the management technology of pruning plants to form a certain tree structure. Obviously, plastic surgery is done by certain pruning means, and pruning is carried out on the basis of plastic surgery according to certain purpose requirements. Therefore, they are closely related and belong to the technical measures required for certain cultivation and management purposes. ? When pruning and shaping garden trees, the following principles should be followed:

( 1)? Landscape requirements? Different pruning and shaping measures will bring different effects, and different greening purposes have their special pruning and shaping requirements. Therefore, first of all, it is necessary to clarify the use requirements of a specific tree in landscaping. For example, Sabina vulgaris of the same species is planted on the lawn alone as ornamental and cultivation timber forest, and the requirements for pruning and shaping are completely different, so the specific pruning methods are different, especially when it is used as a hedge. ? (2)? Growth and development habits of tree species? After defining the purpose requirements, the specific pruning must be carried out according to the growth and development habits of tree species, otherwise it will be counterproductive. Generally speaking, we should pay attention to the following two aspects: ① the growth and flowering habits of tree species. The growth habits of different tree species are very different, so different pruning and shaping measures must be taken. For example, many trees with pointed and conical crowns, such as Populus davidiana, Populus tomentosa, Sabina vulgaris, Ginkgo biloba, etc., have strong apical advantages, and there is an obvious subordinate relationship between the trunk and the main lateral branches. ? For trees with this habit, the central trunk should be kept to make it cylindrical and conical. For some trees that are not very strong at the top, but have strong branching ability, they are easy to form clumps, such as osmanthus fragrans, gardenia, plum blossom and Prunus tomentosa. They can be trimmed into circles and hemispheres. ? For positive tree species that like light, such as plum, peach, cherry and plum. If the purpose is to make it stronger, it is appropriate to use natural and happy pruning and shaping methods. Such as Sophora japonica, ebony and so on. The main branches should be in a horizontal disk shape to make the crown open in an umbrella shape. ? The germination ability and callus ability of each tree species have a great relationship with the overall shear resistance. Most tree species with strong budding and strong branches can withstand multiple pruning, such as water wax, Platanus acerifolia, Buxus macrophylla, Sabina vulgaris and Ligustrum lucidum. Accordingly, tree species with weak germination or callus ability, such as Platanus acerifolia, Osmanthus fragrans, Magnolia grandiflora and Ilex cornuta, should be cut less or lightly.

Pruning and shaping technology should be often used in gardens to adjust the growth of branches in different parts to maintain the balance of crown, and it must be operated according to the growth relationship between main branches and lateral branches on plants. ? According to the growth law between branches of trees, on the same plant, the stronger the main branch, the more new shoots, the larger the leaf area, and the stronger the ability to make organic nutrients and absorb inorganic nutrients, thus making the main branch grow sturdily. On the contrary, the relatively weak main branches grow weaker and weaker because of lack of new shoots and poor nutritional conditions. When pruning measures are taken to make the growth potential of each main branch close to balance, the transfer of nutrients from strong main branches to weak main branches should be inhibited. So, the principle of holistic cutting is to cut off the strong main branches? (? That is, keep it short? )? Weak main branches, weak scissors? (that is, stay a little longer? )? In this way, we can adjust growth and gradually balance it.

In order to adjust the growth potential of lateral branches, we should master the principles of strong lateral branches and weak lateral branches. This is because lateral branches are the basis of flowering and fruiting. When the lateral branches grow too strong or too weak, they are not easy to become flower branches. Therefore, the weak pruning of the strong can produce appropriate growth inhibition and concentrate nutrients, which is conducive to the differentiation of flower buds. The growth and development of flowers and fruits also inhibited the growth of strong side branches. Strong shearing of weak lateral branches can make nutrients highly concentrated, and top dominant stimulation can produce strong branches, thus regulating the growth of lateral branches.

Flower bud insertion and flowering habits of tree species vary greatly. Some flowers first and then leaves, some leaves first and then flowers, some single buds, some mixed buds, some flower buds inserted in the middle and lower parts of branches, and some inserted in branches. These ever-changing differences are all factors that should be considered when pruning, otherwise it is likely to cause adverse consequences. ?

How old is this plant? (? Life cycle? )? . When the plant is in its infancy, it is not suitable for intensive pruning because of its strong growth potential. Otherwise, the autumn branches will not fully mature, which will reduce the cold resistance and delay the flowering period. Therefore, except for special needs, young trees can only be cut weakly, not forcefully. ? Adult trees are in the stage of vigorous flowering and fruiting, and their crowns are beautiful and complete. The purpose of pruning and shaping in this period is to keep the plants robust and perfect, so as to keep flowering and fruiting and high and stable yield. The key is to cooperate with other management measures and comprehensively use various pruning methods to achieve the purpose of adjusting balance. ? Due to the weak growth potential, the annual growth of old trees is less than the death. When pruning, we should give priority to strong pruning to stimulate its growth potential, and be good at using long branches to achieve the purpose of rejuvenation.

Characteristics of environmental conditions for tree growth Because the growth and development of trees are closely related to environmental conditions, even if they have the same requirements for landscaping purposes, they will be different in specific pruning and shaping due to different conditions. For example, it is better to cut a single tree into a natural shape when the land is fertile, but when the soil is barren, it is necessary to appropriately reduce the branching points so that the main branches can form a crown in a lower place. In windy places, it is necessary to reduce the height of the trunk and properly sparse the crown.