Street trees, like other trees, have the function of protection and beautification, and at the same time have its unique role in urban community greening. Street trees are the skeleton of urban community greening, connecting all kinds of green spaces scattered in urban communities to form a beautiful and spectacular green whole; Street trees also have the function of organizing traffic, which not only reflects the appearance and local color of urban communities, but also relates to people's physical and mental health. Therefore, it is the unshirkable responsibility of landscape workers to ensure the healthy growth of street trees.
Street trees refer to trees planted neatly on both sides of the road, and each road has the same tree species. In urban communities, the main functions of street trees planted on main roads are to beautify the city appearance, improve the urban microclimate, humidify and cool down in summer, and retain dust and shade. Street trees require straight trunks, elongated branches, open crowns and dense branches.
Generally, the height of the main roads in urban residential areas is 2.8~4.0m, and the suburban roads are 3 ~ 4m or higher. When street trees are fixed, the height of branch points on the same main road should be consistent and uniform, so as not to affect the appearance and management. According to the standards formulated by the electric power department, various pruning techniques are adopted to keep the crown branches and leaves at a safe distance from various lines (as shown in Figure 3-6).
Figure 3-6 Relationship between Street Tree Pruning and Upper Line Figure A- Upper Crown Pruning; Trim on one side of the crown; Lateral pruning under the canopy; Pruning in the middle of the crown
(1) cup-shaped street tree pruning
Cup pruning is a typical crown shape with three branches, six branches and twelve branches, such as Sophora japonica and Platanus acerifolia. After the skeleton is formed, the crown of the tree expands rapidly, thinning and deciphering the collected branches and upright branches, promoting the lateral branches, properly retaining the internal branches and increasing the shading effect.
(2) Pruning of happy street trees
It is mostly used for trees without central axis, and the crown naturally develops. When planting, leave the trunk for 3m or cut it off. After germination in spring, select 3 ~ 5 lateral branches evenly distributed in different directions for short cutting, so as to promote the branches to grow into main branches, and smooth all others. After germination in the second year, 6 ~ 10 lateral branches are selected to grow obliquely in all directions, cut short in parallel, promote secondary lateral branches, and make the crown full and symmetrical.
(3) pruning of natural crown-shaped 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.
1. Branched tree with central leadership
Such trees include poplar, ginkgo, Metasequoia glyptostroboides, Platycladus orientalis, Pinus yunnanensis and Cedar. 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. Tall trees are mostly used in suburbs, and the branch points are above 4 ~ 6 m. If the top of the trunk is damaged, you should choose branches that have been growing vertically or cut them short at strong buds, and erase the lower lateral buds and take out the upright branches to avoid the phenomenon of multiple heads. This kind of tree should be based on thinning and pruning, with as few short sections as possible.
2. Branches without central leadership
Choose tree species with weak trunks, such as early willow and elm. The height of the branch point is generally 2 ~ 3m. Leave 5 ~ 6 main branches, and the spacing between the main branches on each floor is short, so that it naturally grows into an oval or oblate crown. The main objects of pruning every year are dense branches, dead branches, diseased branches and residual branches.
Second, the pruning of shade trees in the courtyard
Shade trees should have a huge crown, a beautiful tree shape and a smooth trunk. When shaping this kind of tree, we should first cultivate a medium-height trunk, which is tall and strong. There is no specific regulation on the trunk height of shade trees, which should mainly meet the requirements of the surrounding environment and also depend on the ecological habits and biological characteristics of tree species. Generally, as a shade tree, the height of the trunk is higher, which should be between 1.8 ~ 2.0m for tourists to move freely under the tree. The trunks of ornamental trees planted in the center of hillsides or flower beds are mostly less than1m.
The crown size and the ratio to the height of shade trees depend on the growth habits and greening requirements of tree species. Shading trees and solitary trees make the crown as large as possible, so as to give full play to their protective effects such as shading, and also prevent some tree species with thin bark from being burned and dried by the sun. It is generally believed that the ratio of the crown of shading trees to the height of trees is more than 2∶3, and it is appropriate to be no less than 1∶2; If the crown is too small, it will affect the growth and health of trees.
There are not many kinds of ornamental trees as shade trees, and most of them use natural trees. During the dormancy period, the branches that are too dense, disabled, sick and dead and the branches that disturb the tree shape are thinned out to cultivate a healthy and tall tree shape; Some also carry out special modeling and trimming according to the requirements of configuration to present better viewing effect.
Third, ornamental flowers and shrubs are trimmed.
(a) when pruning trees with the main purpose of flower viewing, we must consider the flowering habits, flowering positions and flower bud properties.
1. early spring flowering species
Most kinds of flower buds differentiate in summer and autumn of the first year, so flower buds are planted on biennial branches, and some can also form flower buds on perennial branches. The pruning period is mainly dormant, combined with summer pruning, the pruning method is mainly thinning, and other pruning methods are comprehensively applied.
2. Summer and autumn flowering types
The bloom of this tree on the new branch of that year, that is, the flowers and trees that are usually called "leaves first and then flowers", refers to this kind, such as hydrangea, crape myrtle, hibiscus, pearl plum and so on. This kind of tree is generally not pruned in autumn, so as to avoid sprouting and freezing damage after the branches are stimulated. Usually in early spring, before the sap starts to flow. Because of the different types of pruning methods, the combination of short cutting and thinning is the main method. Some trees can bloom for the second time (pearl plum, crape myrtle, etc.). ).
(2) Fruit ornamental category
Gold and silver wood, holly, centipede and so on. Can belong to ornamental shrubs. In fact, these flowers and fruits are ornamental, so the pruning time and method are the same as those in early spring. The difference is that after flowering, it is generally not cut short, mainly to remove too dense branches, so as to facilitate ventilation and light transmission, reduce pests and diseases, and improve the ornamental effect.
(3) Ornamental branches
This kind of tree includes Tang Di, red-headed wood, etc. In order to make its ornamental time long, it is often pruned before germination in early spring and not pruned in winter, so as to give full play to its ornamental function in the long winter. The twigs of this tree are the brightest, and the color of the old stems is often dim. Therefore, it should be cut again every year to promote more new branches, and at the same time, the old stems should be gradually removed and constantly updated.
(4) formal observation class
This kind of tree includes weeping peach, weeping elm, albizzia albizzia, Sophora japonica and so on. , mainly because of their elegant tree shape. Pruning depends on different kinds, such as peaches, elms, locust trees, etc. If you cut it short, there will be no buds, and there will be buds. For example, after the acacia tree is formed, it is only conventional thinning, and generally it will not be cut short.
(5) foliage plants
This kind of trees mainly appreciate their bright leaf colors. Such as forsythia, Ligustrum lucidum, red Berberis, cherries, sour plums, peaches and the like. This kind of tree should be treated differently according to its different growth characteristics. Usually, short cutting can be carried out to promote new branches, and proper ventilation and light transmission can be achieved to achieve ornamental effect.
Four, hedges, ribbon modeling and pruning
Hedges and ribbons play an important role in landscaping, because they can form various shapes and combine with each other to improve the ornamental effect. In addition, the hedge also has the functions of shielding bad viewpoints, isolation, protection, dust prevention and noise prevention. Ribbon is a hedge or ribbon planted by hedge seedlings according to design requirements. Hedge pruning is not only for neatness and beauty, but also for the hedge to grow luxuriantly for a long time. Hedges with different heights adopt different modeling methods, generally including regular and natural.
Hedges and ribbons should be trimmed with clear outline, neat lines, flat top surface, consistent height and vertical sides. If there are special design requirements, it should be trimmed according to the design requirements. When trimming a curved ribbon, make the surface naturally smooth.
Natural pruning
Green walls, high fences and flower fences are widely used. Properly control the height, prune the branches of diseases and insect pests, dead branches and dead branches, let the branches grow, make the branches closely connected, and improve the blocking effect. Natural pruning is also the main way to prevent hedges with thorns such as holly and oranges and flower hedges such as roses. Prune slightly after flowering to keep flowering, and prune dead branches and pests in winter. For tree species with strong germination, such as roses, heavy pruning is carried out after flowering, and the new branches are thick and the hedges are tall and beautiful.
(2) Form pruning
Middle hedges and short hedges are often used to edge lawns and flower beds, or to organize people's flow. This hedge is low. In order to beautify and enrich the landscape, geometric patterns are often used for modeling and trimming (as shown in Figure 3-7), such as rectangle, trapezoid, inverted trapezoid, wavy hedge surface and so on. After the hedge is planted, the height of 1/3 ~ 1/2 is cut off, the flat branches are trimmed, the height and sides are unified, and the lower buds are promoted to sprout branches, forming a low wall with tight branches and dense leaves, which presents three-dimensional beauty.
Figure 3-7 Whole Hedge Pruning
Generally, rectangular shaping is used for word combination and pattern hedges, which require sharp edges, clear boundaries, narrow and consistent hedges, and the number of pruning per year should be more than that of hedges with edges and precautions. The replacement and renewal of branches should be short, without baldness, and the words and patterns should be clear. Cut plants into three-dimensional shapes, such as birds and beasts, archways and pavilions. In order to keep their images realistic, branches should not be allowed to grow at will to destroy their shapes. They should be pruned several times a year.
(3) Hedge pruning period
Hedges of evergreen conifers are usually trimmed in late spring and early summer. In the middle and late April, in order to welcome May Day, a plastic surgery was carried out. Prune every 10 ~ 15d from May to August, especially Ligustrum lucidum. The stubble height of pruning is 65438±0cm higher than that of the last pruning. In order to welcome the "Eleventh" National Day, a plastic surgery was performed from September 20th to 25th. However, the interval between this pruning and the last pruning should be at least 15d.
Verb (abbreviation for verb) pruning of vines
Pruning ornamental flowering vines is generally simple, not as complicated as cultivating grapes in orchards. Pruning of flowering lianas, on the one hand, determines their growth and development habits (tendrils, winding, sucker), on the other hand, determines the application mode.
(1) scaffold type
The most widely used forms of tendrils and twining vines are square, rectangle, circle, polygon and compound. Before plastic surgery, a solid scaffold should be built first, and then vines should be planted next to it. After the tree survives, it will be cut off from the ground to make it send out 3 ~ 4 main vines. After stretching, it will be attracted to the top of the trellis, and its lateral vines will be evenly distributed on the surface of the trellis, thus quickly forming a shade shed. The speed of forming a shade shed determines the species of plants, the size of the shelf surface and the planting density. When planting tree species that are not hardy in cold areas, the weak and aging branches should be cut off in winter, coiled and tied and buried in the soil. It was unearthed in the second year and put on shelves. Cold-resistant tree species do not need to be buried under the frame to prevent cold, as long as the branches that affect viewing are cut off next year.
(2) Gallery style
It is often used for tendrils and winding, and some plants are adsorbed. Because there is a lattice frame on the side of the veranda, in order to cover the frame surface with plants, don't lure the top of the veranda too early, otherwise it is easy to form a gap on the side.
(3) Fence type
Mostly used for tendrils and twining plants, all kinds of roses are widely used in gardens, such as Douglas fir, Ten Sisters, Tang Baiyu and so on. Their branches are long and soft, the length of branches can be chosen at will, and the growth direction can be changed freely. These varieties are extremely resistant to pruning and grow rapidly, and can basically take shape after 2 ~ 3 years of planting. When pruning, twigs, pests and diseases should be drained at any time; Keep it ventilated and transparent, so that it can bloom more.
(4) Attached to the wall
Most adsorptive plants are used as materials, such as Euphorbia humifusa, Lingxiao, Ivy, Euonymus fortunei and so on. The method is simple, just introduce vines into the wall and gradually cover the wall with suction cups or roots. Pruning mainly adopts shearing shrinkage to promote branching, to prevent the base from being empty, and at the same time, conventional thinning should be carried out.