It takes 3-5 years or more 10 years to cultivate street trees and large seedlings for landscaping. Broad-leaved trees, such as poplar, willow, elm, locust, sugar maple, colored wood, Ailanthus altissima, Sophora japonica, linden, Platanus acerifolia, peach tree, phellodendron amurense and walnut. 1. Flat stubble dry cultivation: For deciduous broad-leaved tree species with strong germination, such as Paulownia, Robinia pseudoacacia and Ailanthus altissima, flat stubble is an effective measure to improve dry shape. One year after transplanting, if it is considered that the stem shape of the seedling does not meet the requirements, the growth is not vigorous, or the aboveground part is seriously damaged, the ground can be leveled before germination in spring to make it grow into a strong trunk again. It is best to level the stubble in the northern area before the soil thaws in early spring. The incision should be smooth to facilitate wound healing and germination. After stubble leveling, loose soil with a thickness of 3-5 cm can be covered to prevent the wound from drying due to excessive evaporation of water. After that, many sprouting strips will grow on the root plants of the seedlings. When the sprout grows to a height of about 15 cm, the plant can be fixed, one vigorous sprout can be kept, and the rest can be removed. Strengthening tending management can generally reach the height required by seedling trunk in that year. 2. Heading, pruning and dry cultivation: dry cultivation is very important for garden seedlings. Generally, large seedlings have a certain trunk height, but for various reasons, the trunk can't grow upright and can't reach the required height. In this case, the method of stubble leveling is not adopted, but the required trunk height is achieved by heading and pruning. Conifers are uniaxially branched, and the top is extremely favorable. With a little management, they can grow into completely straight seedlings, while the tops of broad-leaved trees (especially in the case of sparse planting) are easy to branch, so it is necessary to take necessary measures to cultivate completely straight seedlings. In order to cultivate the dry shape of seedlings, we must first understand the reasons why seedlings can not form tall, straight and dry shapes under general growth conditions, and then take effective measures to overcome these shortcomings. (1) Because of the branching habit of seedlings, the cultivation of excellent stem shape is hindered. Trees with combined branches, such as elm, Robinia pseudoacacia and Platanus acerifolia, have no real terminal buds in their new shoots, and their shoots are not full, but their buds are thin. Therefore, the top advantage is not obvious, the middle part of the new shoot grows fully and the buds are full. Under normal circumstances, the weak buds at the top of new shoots often fail to form the most vigorous branches when they germinate in spring, while the branches extracted from several strong buds in the middle and upper part of new shoots grow vigorously, even exceeding the branches extracted from the terminal buds. Therefore, an obvious trunk cannot be formed. Pruning method: when the buds swell in spring, cut off the underdeveloped top, choose the place where the buds are full in the middle and upper part of the top, cut off the buds with upward buds, and wipe off the 4-5 buds below, so as to promote the emergence of vigorous new buds at the cut. For example, in early spring, after the top of the stem is cut short and smeared with buds, the buds below still send out tall and strong branches, so it is necessary to cut short and weaken its growth to ensure the advantage of the top. Quasi-dichotomous tree species, such as paulownia, catalpa, etc. The tip of the new bud is thin and extremely weak, and there are opposite lateral buds below. Under the condition of natural growth, the top of the seedling trunk can not grow, and the opposite lateral buds near the top send out a pair of thick lateral branches inclined to both sides, so that the trunk can not continue to grow upward. Pruning method: when the bud is about to sprout in spring, choose a bud with upward bud tip and vigorous growth from the top of the top tip, obliquely cut the top tip on it, and then wipe off 4-5 pairs of opposite side buds below, so as to ensure that new branches grow upward on the cut bud, which is more than the side branches below, and can continue the trunk. (2) The competition of buds hinders the cultivation of excellent stem shape. Trees with competing branches, such as Robinia pseudoacacia, Platanus acerifolia, Populus canadensis, etc. It is necessary to deal with competitive branches in time to cultivate excellent trunks and continue to grow in a uniaxial direction. According to the branching habit of trees, the cultivation trunk should be pruned in advance to prevent competitive branches. If there are competing branches, it is best to cut them short in June, so as to restrain the competing branches and support the top of the trunk. Modification of crown: The methods of shaping and pruning should be different for crowns with different development conditions. (1) Appropriate thinning: The crown of seedlings is basically balanced, and appropriate thinning is mainly adopted during transformation. Sparse the vertical and overgrown branches on the trunk of seedlings, as well as the opposite branches, whorled branches and too dense cross branches, so as not to destroy the normal crown shape and trunk shape. It is also necessary to remove branches that grow weakly and have pests and diseases in the crown. (2) Restrain the strong and help the weak: the crown of uneven development is mainly to restrain the strong and help the weak in the transformation. For robust double-sided large lateral branches, in winter, the vigorous branches and upright branches can be properly loosened, the opening angle of lateral branches can be increased, the head can be changed with back branches, and weak buds or weak branches can be left when cutting short branches to weaken the growth of excessively vigorous large lateral branches. For the weak lateral branches, it is necessary to promote their growth, sparse the dying and dead branches, reduce the opening angle of the lateral branches, replace the head with upright branches, and take appropriate short cutting, cut the mouth and leave full buds to promote the growth of new shoots. (3) Control the growth of big lateral branches: Control the growth of big lateral branches regardless of whether the crown is balanced or not. If the base diameter of the big lateral branch is more than 65,438+0/3 of the trunk diameter of the seedling where it is located, the big lateral branch should be re-cut (including thinning and re-cutting, etc.). ) to inhibit the growth of * * *. (4) Adjusting the extension direction of the lateral branches: Generally speaking, the growth direction indicates the extension direction of the later branches. Therefore, keeping the orientation of cutting buds during short cutting can control the development of new shoots. For example, in order to increase the angle of the lateral branches, the buds located at the side of the branches can be reserved as cutting buds; In order to make the lateral branches develop in the vertical direction, the buds growing upward on the inner side of the branches can be reserved as cutting buds; In order to make the new buds extend to the left or right, let the cut buds grow to the left or right. In order to expand the opening angle of the lateral branches, if the method of simply cutting the lateral buds can't achieve the goal, the method of pushing out the inner buds can be adopted, that is, the second cut bud is selected as the head of the future lateral branches in winter, and the cut buds remain the inner buds. After cutting in the second year, the first branch stands upright and the second branch leans outward. You can put the first branch in winter. There are many branches. When the 1 branch is left under the cutting gate and the second branch stands upright, the third bud can be cultivated as an extension branch, and the 1 branch and the second branch can be cut off in winter. This method is called double-bud kick. In addition, in the summer when the branches grow vigorously, measures such as binding and pulling can be adopted to change the position and extension direction of the lateral branches. After the end of the growth period, the branches are lignified, basically shaped, and can be loosened after being tied. (5) Crown-to-height ratio: The purpose of determining the crown-to-height ratio (the ratio of seedling crown length to seedling height) is, on the one hand, to maintain proper seedling crown width and leaf area to ensure vigorous growth of seedlings; On the other hand, it is necessary to gradually eliminate the lateral branches at the base of seedling crown during the growth process, so as to ensure the continuous growth of trunk height, reach the required fixed trunk height as soon as possible, and promote the growth of trunk. The value of crown height ratio depends on different tree species, ages and crown width development of seedlings. Generally, the ratio of crown width of negative tree species to evergreen tree species is large; For positive species, deciduous broad-leaved species and fast-growing species, the crown width ratio can be smaller. Landscape trees, especially street trees with "four sides" greening, are mostly fast-growing deciduous broad-leaved trees, such as poplar, paulownia, elm, Sophora japonica, Robinia pseudoacacia, Platanus acerifolia and Toona sinensis. For these tree species, when the height reaches 3 ~ 4 meters, the crown width ratio should be kept at about 3/4. When the seedlings are 5-6 meters high, the crown ratio should be kept at about 2/3; When the seedling height is more than 7 meters, the ratio of crown height should be kept at about 1/2. After the height of the trunk reaches about 2 meters, the big lateral branches and small lateral branches at the base of the seedling crown can be pruned every 3-4 years. The height of seedlings is increasing year by year, so it is necessary to gradually prune the branches planted at the base of seedlings to keep the trunk growing and reach a fixed height. When the trunk reaches a fixed stem height, the lateral branches of the above parts may not be pruned, but the crown of the seedling can be enlarged as much as possible, the nutritional area can be increased, and the height and thickness of the seedling can be promoted. I'm really not good at marketing. I'm sorry