Because different greening purposes have special requirements for shaping trees, we should first make clear the purpose requirements of trees in landscaping, and then choose appropriate pruning and shaping methods according to this requirement.

(2) According to the growth and development habits of tree species

Young trees are in a period of vigorous vegetative growth. At this time, except for special needs, it is generally not appropriate to carry out strength pruning. Adult trees are in a vigorous flowering and fruiting period. The purpose of pruning and shaping at this time is to keep the plants robust and perfect, and to keep the flowering and fruiting activities flourishing, high and stable for a long time. Therefore, the key is to comprehensively use various pruning methods and cooperate with other management measures to achieve the purpose of adjusting the balance. Because the growth of trees is weak during the aging period, the annual growth is less than the death, and it is in the stage of centripetal growth and renewal. Therefore, pruning should be based on strong shearing to stimulate its growth, and it is necessary to be good at using long branches to achieve the purpose of rejuvenation.

For tree species with strong terminal bud growth potential and obvious subordinate relationship between trunk and main lateral branches, such as Populus tomentosa and Ginkgo biloba, the central trunk should be reserved for shaping, and it should be cylindrical or conical. For tree species with weak top growth potential but strong branching ability, such as osmanthus fragrans and Eucommia ulmoides, which are easy to form tufted crowns, they can be pruned into spheres and hemispheres. For trees that like light, such as plum, peach and plum. You can use natural and happy pruning and shaping methods. For tree species with spreading habits, such as Sophora japonica and ebony. The main branches should be made into a horizontal disc shape, so that the crown of the tree opens in an umbrella shape. Tree species with strong budding and branching ability, such as Chinese parasol and magnolia, should be pruned less or only lightly.

In order to keep the growth potential between the main branches of trees close to balance, we should suppress the strong main branches and divert nutrients to the weak main branches. Therefore, the principle of pruning is "strong branches and strong cuts, weak branches and weak cuts." Because lateral branches are the basis of flowering and fruiting, too strong or too weak can not be transformed into flowering branches, so weak pruning can be carried out to inhibit the growth of strong lateral branches; In order to stimulate weak branches to send out strong branches, strong shearing can be carried out to adjust the growth of side branches.

The flower bud position and flowering habits of tree species are very different, some of them bloom first and then leave, while others leave first and then open; Some are simple flower buds, some are mixed flower buds; Some buds are inserted in the middle or lower part of the branch, while others are inserted in the tip of the branch. These ever-changing differences are all factors to be considered in pruning, otherwise it is likely to cause greater losses.

(three) according to the characteristics of the environmental conditions for the growth of trees.

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, in fertile land, it is best to cut a single tree into a natural shape, but in places where the soil is barren or the groundwater level is high, the branch point should be appropriately lowered so that the main branch begins to form a crown at a lower place; In windy places, the height of the trunk should also be reduced, and the crown should be properly sparse.