Street trees refer to trees planted neatly on both sides of the road, and each road has the same tree species. In cities, street trees planted on main roads are mainly used to beautify the city appearance, improve the urban microclimate, increase temperature and decrease temperature in summer, retain dust and provide shade. Street trees require spreading branches, open crowns and dense branches.

The crown shape depends on the overhead lines and traffic conditions of the planting site. On the main roads and general roads, regular tree crowns are used and trimmed to form three-dimensional geometric shapes such as cups and open hearts.

Natural crowns can be used on roads or narrow lanes where no motor vehicles pass. After planting street trees, they should be pruned every year to enlarge the crown, adjust the extension direction of branches, increase the shading and heat preservation effect, and also consider the use and lighting of buildings.

2. Pruning and shaping of cup-shaped street trees

The cup-shaped street tree is a typical crown shape with three * six strands and twelve branches. After germination, select 3-5 branches with different directions and evenly distributed at an angle of 45 with the trunk as the main branches, and peel or thin the rest in stages. In winter, the main branches are cut into pieces of 80 cm- 100 cm, and the cut buds remain on the side and on the same plane.

In the summer of the following year, the young paulownia has a strong top advantage by stripping buds and thinning branches. When the main branch grows obliquely, lateral buds and back buds tend to grow upright branches to prevent lateral buds or lower buds from growing upright at the incision.

In the winter of the third year, the 1-2 lateral branches on both sides of the main branch were selected as extension branches, which were cut at 80 cm- 100 cm, and the cut buds were left on the branches, and the original temporary reserved upright branches and cross branches were removed. After repeated pruning, a cup-shaped crown can be formed after 3-5 years.

3. Pruning and modeling of happy street trees

It is mostly used for trees with no central spindle or neck bud, natural crown expansion and self-shearing. When planting, leave the trunk 3 meters or cut it off. After germination in spring, select 3-5 evenly distributed lateral branches in different directions for short cutting, so as to promote the branches to grow into main branches, and smooth all others.

During the growing season, pay attention to wiping off the buds on the main branches, and keep 3-5 side branches with appropriate directions and even distribution. After germination in the second year, choose to leave 6- 10 lateral branches, make them incline in all directions, and cut short to promote the secondary lateral branches, so as to make the crown full and symmetrical.

4. Pruning and modeling of natural crown street trees

Under the condition that traffic and other public facilities are not hindered, when trees have any growth conditions, street trees often adopt natural crown shapes, such as tower, oval, oblate and so on.

Street trees with central main branches. Such as poplar, Metasequoia glyptostroboides, Platycladus orientalis, money pine, cedar, Pterocarya stenoptera and so on. The height of the branching point depends on the characteristics of tree species and tree specifications, and the terminal buds should be protected from growing upward during cultivation.

If the top of the trunk is damaged, the branches that have been growing vertically should be selected or cut short at the strong buds, and the lower lateral buds should be erased, and the upright branches should be taken out to avoid the phenomenon of multiple heads. Broad-leaved trees such as Populus tomentosa are not resistant to heavy plastering or cutting, and thinning should be given priority to in winter.

When pruning, an appropriate ratio of crown to stem should be maintained. Generally, the crown height accounts for 3/5 and the trunk height (below the branch point) accounts for 2/5. The height of the branch point next to expressway should be at least 2.8m Pay attention to that the bottom three branches should be staggered up and down, with symmetrical directions and appropriate angles.