A Detailed Guide to the Maintenance Methods for Greening Plants and Flowers Along Expressways
Greening maintenance and management along expressways is an important part of the greening work of high-grade highways, playing a significant role in maintaining the landscape effect of expressway greening, giving play to ecological functions, and ensuring driving safety. Due to the specific environmental conditions of expressways, the various flowers, grasses and trees planted must achieve normal growth and reflect the greening effect, so maintenance and management work must be strengthened. Otherwise, no matter how well the species are selected and planted, the beautification effect cannot be achieved. Therefore, as expressway greening receives more and more attention, it is very necessary to further emphasise and study the maintenance and management techniques of greening, and then establish a whole set of effective measures.
Water Management for Expressway Greening Plants
At present, in the greening maintenance and management of expressway green belts, especially the central median, because the line is long, the quantity is large, there is no natural sprinkler irrigation system, the soil water-holding capacity is small, and the soil is mostly miscellaneous soil left over from road construction, the water needed by the flowers, grasses and trees in the central median mainly depends on manual supply.
In daily maintenance and management, the number of waterings depends on weather conditions and drought conditions, with the principle of ensuring normal growth of various plants. When natural rainfall is low, drought is particularly likely to occur, so the number of waterings during the growing season, that is, from April to October, must be well controlled; for watering during the dormant period, that is, the freezing water in early and mid-November, and the thawing water from mid-to-late February to early March, each irrigation should have a water depth of 15 to 20 cm; for single-plant planting, each hole should be irrigated with 0.15 to 0.2 m. If the water volume is insufficient because the pit is small, it can be watered twice in succession; the water volume must not be too small, and only the surface must not be watered.
Watering should be carried out in sequence to prevent missed watering. Watering must be timely and must not wait until the drought is especially severe. If conditions permit, after watering, the soil should be loosened and weeds removed in good time, which not only reduces soil moisture evaporation, but also reduces competition between weeds and trees for water and nutrients, helping to preserve soil moisture, improve aeration and promote well-developed root systems. Lawns in courtyards and interchanges should be watered as soon as they dry, while the turf in the central median is generally watered together with the trees.
Nutrient Management for Expressway Greening Plants
When water is supplied normally, to ensure normal growth and development of plants, corresponding nutrient elements and nutrient substances must be supplied. For the central median, because there are many trees and the line is long, if farmyard manure is used, the amount required is too large, so foliar fertiliser is best. In courtyards, interchange ramps, plazas and other areas where the area is concentrated and the soil is better, the amount and frequency of fertilisation can be reduced accordingly.
Base fertiliser is generally applied in late autumn and early winter, when the trees are in the dormant period from the root crown upward, while the underground part is still in its peak period, which is conducive to healing root wounds and also increases soil porosity, helping to preserve soil moisture.
The season for topdressing should be determined according to the growth characteristics of the plants. Because expressways have a relatively long mileage, it is advisable to topdress twice a year, preferably organically combined with irrigation work. Topdressing is generally carried out before the end of April to June, and should not be too late, otherwise it is likely to cause shoot withering in trees, which is unfavourable for overwintering. The fertiliser composition should be mainly N, P and K, and after fertilisation it is best to follow with watering to avoid loss of fertiliser efficiency.
Shaping and Pruning of Expressway Greening Plants
Vehicle speeds on expressways are high and the space is enclosed, so it must be ensured that greening plants cannot affect drivers' driving safety. Therefore, greening plants in the central green belt, side slopes, interchanges and other areas must be regularly pruned in a timely manner.
Attention should be paid to the pruning time of flowering shrubs. For those that bloom first and then leaf out, such as elm-leaved spirea (Prunus triloba) and redbud (Cercis chinensis), the old branches should be compressed and pruned after flowering in spring, and weak branches should be appropriately thinned to promote strong branches and benefit flowering the following year. The pruning of trees and shrubs is mainly to improve the survival rate and to cultivate tree form, while also reducing natural damage. Therefore, under the premise that the crown does not affect aesthetics, appropriate heavy pruning should be carried out. Growing-season pruning is generally carried out from May to June, and dormant-season pruning is generally carried out from October to November. However, note that juniper and Chinese juniper types in the central median grow relatively slowly, so they are generally pruned once a year from October to November; boxwood must be pruned every year during both the growing season and the dormant season.
For the pruning of boxwood and Chinese juniper in the central median, the horizontal plane must be kept level in one line, while the two sides should have a slight inclination, that is, the cross-section is a trapezoid (narrow at the top and wide at the bottom). This is conducive to photosynthesis and prevents the lower part from becoming bare. Juniper has a better tree form, so only the top is pruned to keep it level. Diseased and insect-damaged branches, dead and dry branches, and branches extending out below the steel plate should all be pruned in a timely manner. At the same time, miscellaneous trees and twining objects should be removed. For the pruning of trees on greening platforms, except for evergreen tree species such as pines and cypresses, which are generally not pruned, the remaining tree species should be artificially pruned according to their natural growth form. For example, for red-leaf plum (Prunus cerasifera), remove sprouting branches and buds on the trunk; for Chinese pagoda tree (Sophora japonica var. pendula), remove upright branches at the top and prune drooping branches; for Chinese privet (Ligustrum sinense) that affects driving, use heavy pruning and shaping during the dormant period. However, all seedlings should have diseased and insect-damaged branches, dead and dry branches and the like removed.
For the shaping and pruning of trees in interchange areas, courtyards, toll plazas and other places, the principle of "varied shapes, beautiful and elegant" should be followed, and methods should be determined according to the buildings, terrain and landforms in the environment. The original design pattern shapes should also be maintained, depicting garden art patterns with different styles. When pruning, add branches and colour as much as possible.
Pest and Disease Control for Expressway Greening Plants
Because expressway greening has a long line and a large area, maintenance and management are difficult, so pests and diseases are very hard to prevent. Therefore, frequent inspections should be carried out, and once pests or diseases are found, they should be controlled in a timely manner. If not controlled in time, they will spread rapidly. Prevention should be the main approach, with control combined with prevention.
In design, attention should be paid to the rationality of plant arrangement in green spaces. For example, poplars and willows should not be planted singly over long distances, and cypress types should not be arranged close to fruit trees such as apples and pears. In design, mixed planting should be emphasised to prevent the occurrence of pests and diseases caused by improper arrangement. Do a good job of forecasting and reporting in ordinary times, so as to detect early and treat early, which can achieve twice the result with half the effort.
Preventive pesticide spraying should be carried out once each in March and October every year. Spraying should be carried out on sunny, windless mornings or afternoons; when using pesticides, be "skilful, accurate and firm"; do not use a single pesticide for a long time; apply the right pesticide for the symptoms and do not use pesticides blindly; the concentration when using pesticides should be moderate; when spraying, spray evenly from the upper side and underside of leaves, with no omissions. In actual work, biological pesticides and chemical pesticides should be reasonably selected, making the best use of advantages and avoiding disadvantages, and giving full play to the superiority of pesticides; in autumn, apply a coating of fine lime slurry once on the trunk from the ground to a height of about 1 m, which can not only prevent fungal rot, but also increase the beautifying effect.
Expressway Greening Design and Maintenance Management
With the continuous development of the economy, expressway construction has entered a brand-new era, and several more expressways in our province are about to open one after another. Following this, what we need to continuously explore in greater depth is how to compensate for the impact of expressways on the environment, and how to beautify expressways and improve the overall service level of expressways. Based on many years of experience in greening work, the author has written this article to discuss with peers.
1 Terrain, Landforms and Ecological Characteristics
Expressway green spaces can be divided into three types: first, median green space; second, interchange green space; third, side slope (slope toe) green space. Because the environments and functions of the green spaces are all different, the terrain, landforms and ecology have the following characteristics:
(1) In terms of terrain and landforms, median and side slope green spaces are relatively simple, while interchange green spaces are more complex, not only having flat land and gentle slopes, but also often containing structures such as pools and longitudinal and transverse artificial channels. These special terrains and landforms require special greening designs to adapt to them.
(2) The ecological conditions of expressway green spaces are more severe. Notably, expressway green spaces have strong solar radiation for long periods during the day, so the average daytime temperature is relatively high and air humidity is low, while at night the temperature drops quickly, and plants are prone to freezing damage in winter. Moreover, water supply for expressway green spaces is relatively difficult, generally relying only on rainwater, soil moisture is scarce, and the green space soil contains construction waste left during construction, while the backfill soil is mostly raw soil, making it difficult to meet the requirements for planting and growth.
2 Design Principles
Expressway green spaces should follow the principle of "adapting to local conditions, adapting to road conditions, coordinating the landscape, and combining trees, shrubs, flowers and grasses for easy maintenance", striving to provide road users with an efficient and harmonious traffic environment. Thereby improving the ecological benefits and landscape effects of expressways.
2.1 Using Plants as the Main Element for Landscape Creation
Plant-based landscape creation can not only improve the ecological environment of expressways, playing a role in cooling, increasing air humidity, improving the environment, eliminating noise, purifying air and so on, but can also change terrain and landforms, and can also screen some unsightly artificial structures, making the rigid road landscape full of vitality. In 1993, under the unified planning of the provincial government, the key greening project - the greening project on both wings of the Shenyang-Dalian Expressway - formed a greening pattern combining belts, patches and network points. Along the Shenyang-Dalian line, 50 m wide green belts were built on both wings along the road, forming a high-grade greening landscape of "scenery within the belt, belt within the scenery". For example: the two-wing forest belt greening at the 103-130 kin section under the Anshan management section is lush and shady in spring. Whenever driving through this section, one always feels a sense of freshness, safety and softness, and it also reduces driver fatigue, so we should continuously improve landscape creation measures and add more green to the road.
2.2 Designing from the Overall Effect
In order to set off the grand momentum of the expressway and at the same time adapt to the visual requirements of road users viewing the scenery in an instant, a landscape design using large colour blocks is more suitable. It not only has a striking overall effect and an open, concise landscape, but planting the same plants in patches and forest blocks will also create a good growth environment for plant communities. At the same time, it improves the plant survival rate (such as mixed planting of coniferous and broad-leaved trees, trees and shrubs in each interchange area). In addition, because expressway green spaces are linear, the choice of composition should ensure that the green spaces along the entire route have a unified and coordinated feel, achieving change within unity and improving the overall greening effect of the road landscape.
3 Composition Methods
Among expressway green spaces, the composition methods of median and side slope green spaces are relatively simple, mainly belt-shaped. The composition of interchange green spaces is more complex, with three common types: 1) formal style; 2) natural style; 3) abstract style (between formal and natural styles). The composition of the Shenyang-Dalian road is mainly abstract style. This gives the greening landscape a composition concept with clear and concise pattern outlines, great momentum, and landscape connotations that are easily coordinated with the alignment of interchange roads.
4 Selection and Arrangement of Plants
Because the ecological environments of the green spaces are basically similar, according to the special ecological conditions of expressways, stress-resistant native tree species, lawns and flowers should be selected as the main plants, and in terms of growth habits they should have characteristics such as drought tolerance, cold tolerance, barren tolerance and pollution resistance. Plants suitable for the greening purpose should be arranged to enrich the road landscape effect and adapt to the extensive management characteristics of expressway green spaces.
4.1 Median Green Space
Greening is mainly functional, with plants mainly being straight-row shrubs, lawns and flowers, and the height should be 1.5-2 m, with the boundary being not blocking the line of sight. At the same time, broad-leaved plants with anti-glare, dust-proof and pruning-tolerant characteristics should be used. In addition, there should be some variation in colour and plant shaping, such as maple, elm-leaved spirea (Prunus triloba), lilac, prickly rose and water wax, and planting patterns should also be arranged according to the alignment; for straight sections: because the lights of vehicles travelling in opposite directions at night do not greatly affect each other, the shrub spacing should preferably be 4 m to provide space for plant growth; for curve sections, the opposite is true. The shrub spacing should preferably be 2 m, or they should be planted as hedges. The planting length of each plant should preferably be between 10-15 km, which not only meets traffic safety requirements but also benefits daily maintenance and disease control work.
4.2 Interchange Green Space
Greening aims to combine functionality and beautification. In order to enrich the three-dimensional layers of interchange green spaces and achieve "evergreen in all four seasons, with flowers in three seasons", trees and shrubs are combined with coniferous and broad-leaved flowers and grasses, with large-area skilful mass planting as the main approach according to the composition, and cluster planting or accent planting of plants with different seasonal colour leaves, flowers and fruits, making the overall view strongly coloured and open, forming a multi-layered mixed community, and making the facade layers of the entire green space even richer.
4.3 Side Slope (Slope Toe) Green Space
Greening aims to stabilise soil and protect slopes, prevent erosion and improve the landscape. Due to the influence of soil conditions, slope-protection plants should be selected that are drought-tolerant, highly adaptable, have well-developed root systems, strong sprouting ability, are easy to survive and easy to manage. The planting points should be kept 1.5-2 m from the road shoulder, with triangular arrangement (50 cm X 50 cm). The planting points of trees should be kept 4-5 m from the road shoulder to avoid autumn leaves scattering with the wind onto the parking lane surface and affecting daily maintenance and management.
5 Maintenance Management of Greening
The overall greening design has been fully implemented in highway construction. It can be said that the greening work has only just begun. Therefore, people summarise the relationship between planting and maintenance as "three parts planting, seven parts management", which is to say that maintenance and management work is the key to consolidating greening results.
5.1 Classification of Greening Maintenance
According to the location of the green space and its impact on the traffic environment, green space maintenance work can be divided by importance into two categories:
The first category: key areas. Because of traffic safety, the central median must maintain plant height, and at the same time attention must be paid to horticultural shaping. In addition, for areas that are frequently pruned and plants within the visual range of intersections, in addition to one physiological pruning each year (shaping in winter and spring), timely pruning must also be carried out from the perspective of safety according to plant growth conditions. Because the soil layer is relatively thin and its ability to retain water and fertiliser is poor, water and fertiliser management need to be strengthened in dry seasons.
The second category: non-key areas, such as interchanges and side slopes (slope toes). These areas have little impact on traffic safety, and shaping and physiological pruning are carried out once each in spring and autumn every year.
5.2 Strengthening Water and Fertiliser Management
Water is the lifeblood of all growing things, and fertiliser is a beneficial measure for improving plant growth conditions and raising soil fertility. Therefore, plant growth must have relatively sufficient water and fertile soil for plants to thrive. Therefore, spring and winter irrigation must be strengthened to prevent physiological drought, and watering throughout the year depends on drought conditions. Topdressing must be maintained twice to consolidate and improve the greening effect.
6 Pest and Disease Control
Pest and disease control cannot be ignored in greening maintenance and management either. Every plant will have its common diseases. Once infected by disease or pests, it may spread and expand rapidly among the same species in a short time, bringing greater difficulty to maintenance work and causing huge waste of manpower and material resources. Therefore, we must grasp the occurrence and development patterns of plant pests and diseases in the areas under our jurisdiction and achieve integrated control, with prevention as the main approach. Therefore, when designing and arranging plants, relevant factors such as mutual parasitism of diseases among plant populations must be considered. In addition, daily inspections should be strengthened.
7 Conclusion
The greening project of the Shenyang-Dalian Expressway has been completed, and the expressway greening model is in a stage of continuous improvement and development. However, as people's ideological awareness constantly changes and their appreciation taste continuously rises, adjusting the highway landscape to gradually approach perfection and achieve coordination between road and scenery, smoothness and safety, and comfort and beauty is a issue for greening workers to jointly investigate and discuss in the future.
In short, we must continuously improve the design concept of expressway greening. Strengthen maintenance and management work, improve the level of mechanised maintenance, do a good job in forecasting and reporting, and provide road users with a beautiful, comfortable, safe, smooth and clean driving environment.
References
1 Su Xuehen, Plant Landscape Creation, China Forestry Publishing House, 1989
2 Chen Youmin, Landscape Dendrology, China Forestry Publishing House, 1996
3 Hu Changlong, Landscape Planning and Design, China Agriculture Press, 1995
Expressway Greening Design and Maintenance Management
News from the China Landscape Network on December 14: With the continuous development of the economy, expressway construction has entered a brand-new era, and several more expressways in our province are about to open one after another. Following this, what we need to continuously explore in greater depth is how to compensate for the impact of expressways on the environment, and how to beautify expressways and improve the overall service level of expressways. Based on many years of experience in greening work, the author has written this article to discuss with peers.
1 Terrain, Landforms and Ecological Characteristics
Expressway green spaces can be divided into three types: first, median green space; second, interchange green space; third, side slope (slope toe) green space. Because the environments and functions of the green spaces are all different, the terrain, landforms and ecology have the following characteristics:
(1) In terms of terrain and landforms, median and side slope green spaces are relatively simple, while interchange green spaces are more complex, not only having flat land and gentle slopes, but also often containing structures such as pools and longitudinal and transverse artificial channels. These special terrains and landforms require special greening designs to adapt to them.
(2) The ecological conditions of expressway green spaces are more severe. Notably, expressway green spaces have strong solar radiation for long periods during the day, so the average daytime temperature is relatively high and air humidity is low, while at night the temperature drops quickly, and plants are prone to freezing damage in winter. Moreover, water supply for expressway green spaces is relatively difficult, generally relying only on rainwater, soil moisture is scarce, and the green space soil contains construction waste left during construction, while the backfill soil is mostly raw soil, making it difficult to meet the requirements for planting and growth.
2 Design Principles
Expressway green spaces should follow the principle of "adapting to local conditions, adapting to road conditions, coordinating the landscape, and combining trees, shrubs, flowers and grasses for easy maintenance", striving to provide road users with an efficient and harmonious traffic environment. Thereby improving the ecological benefits and landscape effects of expressways.
2.1 Using Plants as the Main Element for Landscape Creation
Plant-based landscape creation can not only improve the ecological environment of expressways, playing a role in cooling, increasing air humidity, improving the environment, eliminating noise, purifying air and so on, but can also change terrain and landforms, and can also screen some unsightly artificial structures, making the rigid road landscape full of vitality. In 1993, under the unified planning of the provincial government, the key greening project - the greening project on both wings of the Shenyang-Dalian Expressway - formed a greening pattern combining belts, patches and network points. Along the Shenyang-Dalian line, 50 m wide green belts were built on both wings along the road, forming a high-grade greening landscape of "scenery within the belt, belt within the scenery". For example: the two-wing forest belt greening at the 103-130 kin section under the Anshan management section is lush and shady in spring. Whenever driving through this section, one always feels a sense of freshness, safety and softness, and it also reduces driver fatigue, so we should continuously improve landscape creation measures and add more green to the road.
2.2 Designing from the Overall Effect
In order to set off the grand momentum of the expressway and at the same time adapt to the visual requirements of road users viewing the scenery in an instant, a landscape design using large colour blocks is more suitable. It not only has a striking overall effect and an open, concise landscape, but planting the same plants in patches and forest blocks will also create a good growth environment for plant communities. At the same time, it improves the plant survival rate (such as mixed planting of coniferous and broad-leaved trees, trees and shrubs in each interchange area). In addition, because expressway green spaces are linear, the choice of composition should ensure that the green spaces along the entire route have a unified and coordinated feel, achieving change within unity and improving the overall greening effect of the road landscape.
3 Composition Methods
Among expressway green spaces, the composition methods of median and side slope green spaces are relatively simple, mainly belt-shaped. The composition of interchange green spaces is more complex, with three common types: 1) formal style; 2) natural style; 3) abstract style (between formal and natural styles). The composition of the Shenyang-Dalian road is mainly abstract style. This gives the greening landscape a composition concept with clear and concise pattern outlines, great momentum, and landscape connotations that are easily coordinated with the alignment of interchange roads.
4 Selection and Arrangement of Plants
Because the ecological environments of the green spaces are basically similar, according to the special ecological conditions of expressways, stress-resistant native tree species, lawns and flowers should be selected as the main plants, and in terms of growth habits they should have characteristics such as drought tolerance, cold tolerance, barren tolerance and pollution resistance. Plants suitable for the greening purpose should be arranged to enrich the road landscape effect and adapt to the extensive management characteristics of expressway green spaces.
4.1 Median Green Space
Greening is mainly functional, with plants mainly being straight-row shrubs, lawns and flowers, and the height should be 1.5-2 m, with the boundary being not blocking the line of sight. At the same time, broad-leaved plants with anti-glare, dust-proof and pruning-tolerant characteristics should be used. In addition, there should be some variation in colour and plant shaping, such as maple, elm-leaved spirea (Prunus triloba), lilac, prickly rose and water wax, and planting patterns should also be arranged according to the alignment; for straight sections: because the lights of vehicles travelling in opposite directions at night do not greatly affect each other, the shrub spacing should preferably be 4 m to provide space for plant growth; for curve sections, the opposite is true. The shrub spacing should preferably be 2 m, or they should be planted as hedges. The planting length of each plant should preferably be between 10-15 km, which not only meets traffic safety requirements but also benefits daily maintenance and disease control work.
4.2 Interchange Green Space
Greening aims to combine functionality and beautification. In order to enrich the three-dimensional layers of interchange green spaces and achieve "evergreen in all four seasons, with flowers in three seasons", trees and shrubs are combined with coniferous and broad-leaved flowers and grasses, with large-area skilful mass planting as the main approach according to the composition, and cluster planting or accent planting of plants with different seasonal colour leaves, flowers and fruits, making the overall view strongly coloured and open, forming a multi-layered mixed community, and making the facade layers of the entire green space even richer.
4.3 Side Slope (Slope Toe) Green Space
Greening aims to stabilise soil and protect slopes, prevent erosion and improve the landscape. Due to the influence of soil conditions, slope-protection plants should be selected that are drought-tolerant, highly adaptable, have well-developed root systems, strong sprouting ability, are easy to survive and easy to manage. The planting points should be kept 1.5-2 m from the road shoulder, with triangular arrangement (50 cm X 50 cm). The planting points of trees should be kept 4-5 m from the road shoulder to avoid autumn leaves scattering with the wind onto the parking lane surface and affecting daily maintenance and management.
5 Maintenance Management of Greening
The overall greening design has been fully implemented in highway construction. It can be said that the greening work has only just begun. Therefore, people summarise the relationship between planting and maintenance as "three parts planting, seven parts management", which is to say that maintenance and management work is the key to consolidating greening results.
5.1 Classification of Greening Maintenance
According to the location of the green space and its impact on the traffic environment, green space maintenance work can be divided by importance into two categories:
The first category: key areas. Because of traffic safety, the central median must maintain plant height, and at the same time attention must be paid to horticultural shaping. In addition, for areas that are frequently pruned and plants within the visual range of intersections, in addition to one physiological pruning each year (shaping in winter and spring), timely pruning must also be carried out from the perspective of safety according to plant growth conditions. Because the soil layer is relatively thin and its ability to retain water and fertiliser is poor, water and fertiliser management need to be strengthened in dry seasons.
The second category: non-key areas, such as interchanges and side slopes (slope toes). These areas have little impact on traffic safety, and shaping and physiological pruning are carried out once each in spring and autumn every year.
5.2 Strengthening Water and Fertiliser Management
Water is the lifeblood of all growing things, and fertiliser is a beneficial measure for improving plant growth conditions and raising soil fertility. Therefore, plant growth must have relatively sufficient water and fertile soil for plants to thrive. Therefore, spring and winter irrigation must be strengthened to prevent physiological drought, and watering throughout the year depends on drought conditions. Topdressing must be maintained twice to consolidate and improve the greening effect.
6 Pest and Disease Control
Pest and disease control cannot be ignored in greening maintenance and management either. Every plant will have its common diseases. Once infected by disease or pests, it may spread and expand rapidly among the same species in a short time, bringing greater difficulty to maintenance work and causing huge waste of manpower and material resources. Therefore, we must grasp the occurrence and development patterns of plant pests and diseases in the areas under our jurisdiction and achieve integrated control, with prevention as the main approach. Therefore, when designing and arranging plants, relevant factors such as mutual parasitism of diseases among plant populations must be considered. In addition, daily inspections should be strengthened.
7 Conclusion
The greening project of the Shenyang-Dalian Expressway has been completed, and the expressway greening model is in a stage of continuous improvement and development. However, as people's ideological awareness constantly changes and their appreciation taste continuously rises, adjusting the highway landscape to gradually approach perfection and achieve coordination between road and scenery, smoothness and safety, and comfort and beauty is an issue for greening workers to jointly investigate and discuss in the future.
In short, we must continuously improve the design concept of expressway greening. Strengthen maintenance and management work, improve the level of mechanised maintenance, do a good job in forecasting and reporting, and provide road users with a beautiful, comfortable, safe, smooth and clean driving environment.
References
1 Su Xuehen, Plant Landscape Creation, China Forestry Publishing House, 1989
2 Chen Youmin, Landscape Dendrology, China Forestry Publishing House, 1996
3 Hu Changlong, Landscape Planning and Design, China Agriculture Press, 1995