The concept of street trees followed in history is narrow, which refers to providing shade for pedestrians and vehicles, and planting tall trees, which are generally divided into two types: medium-dry strong (with spindle) and medium-dry weak or not obvious (without spindle). Street trees with strong middle stems are generally planted on streets with wide roads and no high-voltage lines on them, while those with weak middle stems or inconspicuous middle stems are generally planted on streets with narrow streets or high-voltage lines. In modern road greening, we should not only pay attention to the selection and application of tree species, but also consider how to beautify the road while shading trees in hot summer. In fact, in road greening, a large number of flowering shrubs with high ornamental value are planted.
Therefore, the flowering shrubs planted on both sides of the road system should also belong to the category of street trees. Street trees in a narrow sense must have a straight trunk. The height of roadside trees planted on both sides of the road should be 3 ~ 4 meters, so as not to hinder the passage of vehicles; The trunk height of the trees in the garden road or avenue in the park is based on the principle of not affecting the walking of tourists, and the height under the branches is generally about 2 meters. In addition, in places where the groundwater level is high and the soil layer is thin or windy, the trunk and tree height of street trees should be reduced appropriately, and the crown should be reduced accordingly. Never force a certain tree shape because of the pursuit of beauty and charm. Doing so will be counterproductive, the tree will not grow well, but it will not achieve the desired effect. Street trees generally have no special shape except vertical trunk. The common shaping methods are central leading trunk, multi-leading trunk, leaderless trunk and cup-shaped trunk. The basic trunk of street trees and branches that can be selected as main branches are cultivated in nursery stage. When the trunk is fixed, the height of the branch points on the same trunk road should be consistent, so as to make it unified and not affect the appearance and management. The tree shape is formed within 5-6 years after planting. After molding, a large number of pruning is not needed, but only regular pruning (thinning out pests and diseases, aging branches, cross branches, redundant branches, etc.). ) to maintain the ideal tree.
Generally speaking, the crowns of street trees are mostly natural trees, without special plastic work, but with the continuous improvement of urban greening level, the decorative nature of street trees should be considered, so now many cities cut the crowns of street trees into various shapes such as spherical, oblate and regular geometric shapes to improve their ornamental value, and at the same time, they can also reflect the appearance and local color of a city.