A. The Design / Maintenance Interface
The design of a landscape has a direct influence on the type and intensity of work that is required for its proper maintenance. Unfortunately, maintenance of the landscape is often assumed or overlooked during the planning and design phase of a project and therefore little consideration is given to ensuring the landscape can be maintained using cost-effective and environmentally sound maintenance practices.
A lack of maintenance considerations in the design of a landscape commonly results in a site that is more maintenance intensive (i.e., costly) than necessary and/or appropriate for its purpose, and one that requires the routine use of practices that are undesirable (e.g., extensive pesticide use, intensive pruning of plants that grow too large for the spaces they occupy).
When applying integrated pest management (IPM) to a landscape that has not been designed with its maintenance requirements in mind, it is frequently necessary to implement site modifications to reduce or eliminate costly and undesirable maintenance practices. The nature, extent, and expense of such modifications depends on the initial design of the landscape. Although the costs of site modifications are recoverable through the long- term maintenance savings they provide, they do add to the front-end expense of implementing IPM.
Costly and undesirable maintenance practices and the need for site modifications can be minimized or avoided by including maintenance considerations and the use of IPM throughout the planning and design phase of a landscape development project. On such sites the cost of implementing IPM is reduced. Thoughtful landscape design also enhances the quality of a site by freeing maintenance resources for application to high priority work that is often deferred.
The term "design / maintenance interface" refers to the
relationship between the design of a landscape and its maintenance requirements.
The extent and quality of this relationship and the benefits it produces
are determined by the degree to which maintenance considerations (including
the application of IPM) are included in the planning and design stage of
a landscape project.
B. Key Considerations for Low Maintenance,
IPM-based Landscape Designs
It is essential that designers have a thorough understanding of situations and designs that cause maintenance problems, and those that make a landscape easier to maintain. Important considerations for designing a low-maintenance, minimum pesticide use landscape include: proper plant selection and planting design; adequate treatment of the interface between different elements of the design (e. g., where shrub beds, buildings, trees, etc., meet turf); use of geotextiles for weed control, surface stabilization, and material separation; configuration and placement of features; specification and detailing of materials and features; and good construction practices.
In most cases, designing for low-maintenance and utilization of IPM is quite straight forward, the same principles generally apply from site to site, and their application will not significantly increase the design and construction expenses of a project (particularly when life-cycle costs and benefits are considered). In a general sense, it is important that the designer think not only about good aesthetic design and proper construction, but also in terms of maintaining the final product with cost-effective and environmentally sound practices.
An understanding of these design considerations, presented
in the following discussions, will provide a basic framework for planning
landscapes that are both attractive and easy to maintain with minimal use
of pesticides. For the most part, these design concepts offer general ways
of avoiding problems that commonly arise in maintaining urban landscapes.
Many of the details of these principles (e.g., use of materials, configuration)
can be executed in a wide variety of ways. For example, mowing strips might
be concrete or brick, while tree wells can be any shape desired (e.g.,
diamond-shaped is useful for facilitating mowing). As long as the basic
concepts are well understood, designers are encouraged to exercise creativity
in finding new ways of applying them.
1. Plant Selection and Planting Design
Plant selection and planting design are obviously important to the overall success of any landscape design. Plants must, of course, be selected and arranged so the species are compatible and suitable for their specific function, whether this is for aesthetics, screening, shading, etc.; but plants should also be chosen and placed with maintenance considerations in mind.
An understanding of the level of tolerance of specific plants to local insect pests and diseases is critical in designing a landscape that minimizes the use of pesticides. Selecting plants that are susceptible to pest problems will increase the potential need for pest control practices and the likelihood of regular applications of pesticides. On the other hand, selecting plants that are resistant to pest problems will decrease the potential need for pest control treatments, including the use of pesticides.
Planting design is a broad term that refers primarily to the selection and arrangement of plants to serve one or more purposes. When minimizing maintenance requirements and pesticide use are included in the objectives of landscape design, emphasis should be placed on 1.) matching plants to their site conditions, 2.) choosing plants that have few cultural and physical maintenance requirements both generally and in the specific context of the design, 3.) choosing plants that are tolerant of local pests, and 4.) situating plants to facilitate maintenance treatments.
How well a plant will do under particular site conditions is largely determined by its cultural requirements. Because microclimatic conditions often vary within a site regardless of its size (e. g., differences in exposure to sunlight between the north and south sides of even a small building), it is always important when selecting and placing plants to consider factors such as soil type, moisture conditions, and exposure to sun and wind. Plants unsuited to their site conditions will not be healthy and vigorous and therefore require added maintenance treatments to help them grow and/or prevent their loss.
Proper placement of plants also includes consideration of their mature size in relation to their proximity to other site features (e.g., trees with a 50' mature height should not be planted beneath powerlines that are only 30' off the ground; a vigorous, spreading shrub should not be planted too near a sidewalk or entrance). Plants that are too large for their space must be pruned regularly, adding to their routine maint- enance requirements and resulting in poor plant form and often poor health (which reduces the aesthetic quality of the landscape).
Design approach is also an important factor influencing maintenance requirements. Landscape designs can range from formal to naturalistic, and from simple to complex. Large monoculture plantings are more susceptible to insect and disease problems, and infestations are likely to be more severe than in the case of mixed, multi-species plantings.
Likewise, due to the uniformity of texture, color,
and overall appearance of monocultures, insignificant levels of "damage"
(e.g., minor insect pest/disease impacts) are more noticeable and therefore
less acceptable than if such damage were present in a more diverse, informal
design. Also, while replacement plants are highly visible in a fairly mature,
formal design with little plant diversity, new plants may be hardly noticed
in a multi-species, mixed design. In addition, an informal, naturalistic
design approach has the potential to require less general maintenance (e.g.,
pruning, weeding) by virtue of the nature of the design approach as described
2. Treatment of the Interface Between Different Elements of the Design
The interface of different design elements (e.g., where a turf area meets a shrub bed) is often inadequately considered. As a result, maintenance problems are common in these areas and they often require repeated manual, mechanical, and/or chemical treatments. However, the need for such practices can be avoided through thoughtful landscape design.
The term "mowing strip" refers to a hard surface (e. g., concrete, brick) installed along the interface between a turf area and another landscape feature such as a shrub bed or a building wall). "Underlayment" refers to the use of a hard surface under a landscape feature (e.g., a concrete pad or strip under and/or around benches, tables, signs, bicycle racks, fencelines).
In the case of walls, fencelines, tables, benches, etc., mowing strips and underlayments eliminate the need to spray or trim the grass and/or weeds that grow where mowers cannot reach. When placed along the interface between shrub beds and turf areas, mowing strips serve as a barrier to underground rhizomes, and they also reduce the need for edging treatments. (See drawing.)
A tree well is a mulched area around the base of a tree (or a group of trees). Usually tree wells are found on turf areas, but they also are used around trees growing in paved areas.
Tree wells are primarily used to eliminate damage from mowers and weed eaters that are used for trimming the grass or weeds that develop at the base of trees. However, tree wells also provide additional benefits. These include improved plant health and development (not only as a result of reduced damage to the tree, but also from reduced competition presented by grass and weeds that grow around the base of trees and from reduced soil compaction caused by mowing equipment); and reduced requirements for controlling the growth of weeds and turf around the base of trees.
To aid in their maintenance, tree wells can be constructed using specific techniques and materials. These include: 1.) a geotextile weed barrier (see discussion on geotextiles), 2.) a perimeter barrier (e. g., concrete, landscape timbers, metal or plastic edging) around the tree well, and 3.) 2"-4" of mulch on top of the weed barrier. (See drawing.)
If desired, ornamental plants (e.g., annual or perennial flowers; small shrubs) can be added to tree wells to improve their aesthetic quality.
Weeds are a common problem where materials with many joints (e.g., pavers) or gravel are used for walkways, rather than those materials with a more continuous surface (e.g., concrete). Installing edging (e. g., metal, treated wood) along the sides of paths constructed with these materials can reduce the encroachment of weeds into the walkway. This will help minimize weed control treatment needs and help maintain the aesthetic quality of the walkway. The use of edging also provides support for the edge of the pathway and reduces its deterioration by physical wear and tear (from people and/or equipment) and damaging weeds (e.g., horsetail, morningglory). (See drawing.)
Curbing can be placed along the edges of paved areas (e.g., parking lots, driveways) that interface with turf and other planted areas to prevent vehicle damage to ornamental plants (e.g., shrubs, flowers, turf) and to the edge of the pavement. Where pavement is adjacent to turf, it is important that curbs be placed 6"-10" from the edge of the pavement to create a mowing strip. (See drawing.)
3. Use of Geotextiles for Weed Control, Material Separation, and Surface Stabilization
Geotextiles (landscape fabric) can play a valuable role in designing low-maintenance landscapes that require only minimal or no use of herbicides. They can be used for weed control, material separation, and stabilization purposes. Since geotextiles are usually included "within" a complex feature (e.g., under a layer of mulch and around ornamental plantings in a shrub bed), it is highly preferable that they are installed during the initial construction of the feature. However, they can also be retrofitted to many landscape features. Geotextiles can provide significant benefits by reducing maintenance requirements and the need for herbicide use for weed control when installed in shrub beds, tree wells, playgrounds, storage yards, underneath dry-laid pavers, etc. Proper material selection and installation procedures are important to ensure the effectiveness of geotextiles.
Thermally spunbonded fabrics are much more effective than woven or needle punched geotextiles in preventing fine roots from penetrating the fabric. Heavier weight fabrics should be used for sites that do not have frequent maintenance intervals. When installing geotextiles, potentially damaging objects (i.e., large angular rocks; pointed sticks) should be removed from the site and the soil should be graded so the fabric will lay smooth and flat on the ground. Where potentially difficult to control weeds are abundant (e.g., quackgrass), an herbicide may be desirable or necessary to prevent weeds from growing to and through seams and edges from below. In some settings, a shallow trench (3"-4") around the perimeter of the installation site is helpful to hold the edges in place and keep them from becoming exposed. Seams should be overlapped 6"-8" and the fabric should be tightly fitted around any objects. Where fabrics may become exposed and subjected to vandalism they should be pinned firmly to the ground, especially around the perimeter. The fabric should then be covered with 3"-4" of a coarse mulch with few or no "fines" to create an inhospitable environment for weed development. Because ultraviolet light is damaging to most geotextiles, fabrics should always be adequately covered. When installed properly, geotextiles will last indefinitely.
A disadvantage of using geotextiles in shrub beds, tree wells, and other ornamental plantings is that the soil under the fabric becomes relatively inaccessible, making it difficult and time consuming to add amendments for soil improvement. However, this problem can be alleviated by adequately preparing the soil before the fabric is installed. (See drawing showing landscape fabric in a shrub bed.)
Geotextiles can also be used to stabilize surfaces by preventing uneven settling, which is a common problem with pavers and asphalt (i.e., when a load is applied to a single point, such as a footstep, the fabric helps distribute the load).
In addition, geotextiles are frequently placed between
layers of different materials to prevent their mixing (e.g., in walkways
made with pavers, under gravel in electrical substation interiors).
4. Configuration and Placement of Features
The placement and configuration of the elements of a landscape also influence its maintenance requirements. For example, it is a good practice to locate sidewalks according to "desire lines", which are preferred pedestrian access routes based on convenience of traveling from one location to another. Without appropriate placement of sidewalks, people will develop damaging and unsightly paths across turf areas and through ornamental plantings such as shrub beds.
On areas of turf, features such as shrub beds, trees, and other objects should not be placed too close together nor too near the edge of the turf so that they create spaces that are too narrow for efficient mowing with the appropriately sized piece of equipment for the scale of the task (i.e., this may only be a couple feet for a small area mowed by a walk-behind mower but may be several feet for a large area where gang mowers are used). Likewise, features on turf areas should include mowing strips or underlayment, or be placed in a mulched "well" to facilitate mowing.
Regarding configuration, landscapes should be designed
to allow for the access and aid the maneuverability of maintenance equipment
(e.g., acute angles should be avoided in turf areas; wide angles, gentle,
sweeping curves, and straight lines are much easier to mow).
5. Specification and Detailing of Materials and Features
Many different types of materials are available for landscape designs. To minimize maintenance requirements, the most durable and least problematic materials are the obvious choice. While such materials can be more expensive, their positive impact on reducing maintenance needs will make their purchase cost-effective (i.e., life-cycle costing).
The same general principle is also true for detailing
dimensions and construction techniques. For example, concrete sidewalks
should have a well-prepared subgrade, be sufficiently thick, adequately
reinforced, and have properly designed and constructed expansion/contraction
joints to prevent cracking or other damage. Also, when specifying mulch,
use a 2"-4" deep layer of coarse material with few or no "fines" - it is
substantially better for weed control than a shallow layer of fine mulch.
6. Good Construction Practices
Good construction practices provide protection for existing plants, turf areas, and other features that are included in the new design and they preserve topsoil and soil structure in areas that will be graded.
Limits of construction should be clearly shown on construction documents and areas that need protection should be fenced off before work begins. Likewise, heavy construction equipment should not be allowed any closer than 10'-15' outside the dripline of trees that are to remain, nor should this space be used for storage of materials, tools, or equipment.
Where grading is necessary, topsoil should be removed and stockpiled for later use where plants are added to the landscape. When preservation of topsoil is not a specific priority, this valuable resource is often mixed with or completely covered by subsoil, buildings, roads, parking lots, etc.
Source: IPM Access - An Integrated Pest Management Online Service
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