Before Using Graywater to Irrigate a Projects Landscape the Landscape Architect Should Review
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Section 4: Landscape Pattern
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Overview
Landscape Design coordinates the Landscape and Aesthetics Assessment, Landscape and Aesthetics Chief Plan, and other resource with basic landscape concepts to go far at a working landscape and aesthetics design for a projection. Landscape designers bring together ornamental aspects, functional needs, maintenance and sustainability, special ecology goals, relationships to structures, and other factors.
This department contains subsections on ornamental aspects of mural blueprint which include:
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- The Aesthetics of Right-of-Mode Vegetation Anchor: #BCCBQRCQ
- Using Ornamental Grasses Anchor: #NAVFTKJK
- Non-mow Areas Anchor: #XEMQHUHG
- Restoration, Habitat Cosmos, and Naturalization Anchor: #IIPXURES
- Ornamental Landscape Planting Design Guidelines Anchor: #MFGLASCV
- Institute Choice Criteria Anchor: #EMDIBKXP
- Plant Container Sizes Ballast: #UPUBHDOG
- Vandalism Anchor: #OYTGBOVY
- Using Trees in the Roadway Anchor: #LAKTPJNA
- Using Shrubs in the Roadway Ballast: #TCTOBLGW
- Using Groundcovers and Seasonal Colour Plants Anchor: #QWMKUVQM
- Plant Material Human relationship to Structures Ballast: #AJDSCTGT
- Planning and Design for Landscape Maintenance Anchor: #WYEXXDBE
- Plant Irrigation Anchor: #XHGPAHWG
- Irrigation System Types Anchor: #FGFGYDVP
- Designing for Weed Control in Ornamental Landscape Plantings Anchor: #RJIAOEJE
- Pattern Guidelines for Weed Command in Tree Plantings Anchor: #PSSLNMYM
- Blueprint Guidelines for Weed Command in Beds and New Shrub Plantings
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The Aesthetics of Correct-of-Mode Vegetation
The vegetation within the right-of-way, grassy vegetation and wildflowers, is an important part of roadway aesthetics. Grassed rights-of-way in urban areas that are weedy and unkempt give the corridor a neglected appearance and this image may be transferred to the city. Consequently, mowed vegetation that is edged and gratis of litter will lend the roadway and the metropolis a expect of cleanliness and neatness. In most cases, the start pace in improving the aesthetics of the roadway should be to bring the existing vegetation to an acceptable level of appearance.
Roadside vegetation is maintained to accomplish specific goals of sight-distance, articulate view of obstructions, erosion control, and aesthetics. Consequently, blueprint alternatives should exist reviewed to be sure that minimum standards are met for each of these problems. Most roadways are kept mowed to a pinnacle that accomplishes the needs of these problems and meets with the public's expectations for the appearance of the roadside. Public standards should be considered when developing any aesthetic programs that impact roadside vegetation to be sure the proposed enhancements meet with community acceptance.
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Using Ornamental Grasses
Ornamental grasses as office of shrub or mass plantings may be unsuitable in most cases due to the extra maintenance required for cut and removal of annual litter. Plants such equally Pampasgrass have been used successfully in some instances where make clean-upwardly may be delayed for years at a fourth dimension.
In the majority of cases grasses for the roadside shall conform as a minimum to the guidelines and specifications given in the TxDOT Standard Highways Specifications for Construction of Streets and Bridges and the Roadside Vegetation Management Transmission.
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Non-mow Areas
Not-mow areas are portions of roadside that for reasons of safety, utility, or aesthetics are removed from regular mowing and other direction practices such as weeding, pruning, or herbicide control for an indefinite period of time. Sites that are far removed from the travel lanes, are difficult or dangerous to access, are hidden from view, or do not bear upon drive prophylactic are candidates for not-mow status (come across Figure 2-iv).
The designer should exist enlightened that the removal of regular mowing might allow weeds previously held in check to proliferate and present an unkempt appearance. The not-mow option is non synonymous with "restoration," "habitat creation," or "naturalization." Likewise, the adjacent land apply must be considered. Mowing may be required to control invasive species that could proliferate on the right-of-way and invade the side by side state. These weather are about oft encountered on rural rights-of-way.
Effigy 2-4. Vegetation immune to achieve natural growth may be visually acceptable where information technology can be ready dorsum from travel lanes.
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Restoration, Habitat Cosmos, and Naturalization
The apply of the roadside for specialized environmental goals should be carefully considered to be sure that the rubber, sustainability, and life-cycle costs of the project meet department goals and resources. These areas of ecology focus may be defined every bit:
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- Restoration - Restoring a site to the topographic shape, hydrologic function, and plant community that existed in historical times earlier disturbance by man. This exercise is expensive and requires detailed cognition and constant management. Anchor: #GCDKUQOG
- Habitat Creation – Designing and managing plant communities for use as habitat by birds, mammals, reptiles, or insects. Habitat creation involves providing one or all of cover, food, or h2o to a targeted species and requires detailed planning and evolution funding. Where general habitat for wildlife is a goal, the preservation of existing sites is preferable to the development of new habitat. Anchor: #FYMMJALX
- Naturalized Areas – The preservation or establishment of native plant communities either as an aesthetic programme or as role of habitat cosmos. Naturalization seeks to promote or re-introduce native plants to minimize maintenance or ameliorate the aesthetics of the roadside. This volition usually involve the seeding or planting of desirable plants and periodic management to aid in their survival or it may focus on preserving threatened or endangered species. See Figure 2-4 for an example of a natural growth area.
Some portions of the right-of-style may be suitable as office of a re-naturalization project or to remove large areas from routine maintenance. These are usually large areas beyond the minimum distances from pavement edges that do not require regular maintenance and encounter aesthetic and management goals. Near oft these areas are found in large interchanges. In these projects, institute fabric that would non normally be advisable for use in other roadside applications may be desirable as a part of urban reforesting programs, wild fauna habitat, or storm water quality programs.
The institution of naturalized areas in the roadway will oftentimes entail specialized management techniques and scheduling that may require special specifications and contracting procedures. These needs should be advisedly considered in determining the advisable use and design of these features.
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Ornamental Mural Planting Design Guidelines
Plants tin can be an important addition to the right-of-style as an aesthetic enhancement that blends highway structures with the surrounding environment. Figures 2-5 through 2-viii show examples of effective planting design.
The proper utilize of plants tin help brand roadways a positive element in the visual material of our cities. The function and management of transportation corridors place exacting demands on the elements within the roadway. These demands must be thoroughly identified and understood in each design situation. The utilize of plants in the right-of-way must always exist considered in the context of the of import role of safe, maintainable transportation corridors.
Effigy 2-5. Median plantings tin add color and visual separation betwixt driving lanes.
Effigy 2-half-dozen. Bedded plantings in islands tin can add involvement and variety. Height restrictions on plants in these areas are critical.
Figure 2-7. Pedestrian-ways are frequently proficient locations for ornamental plantings.
Effigy 2-viii. Plants are constructive for visually softening tall retaining walls or noise walls.
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Found Pick Criteria
TxDOT is required to apply regionally advisable plants in highway right of fashion beautification projects.
Plants for the right-of-way must also be selected based on their anticipated maintenance needs and their adaptability to the roadside surroundings. The placement of plant fabric in the roadway is of disquisitional importance because of its potential consequence on driver safe. Constitute placement will be discussed in a separate section (see Plant Cloth Human relationship to Structures subsection).
Plants in the roadside are generally viewed at high speeds and are often but part of the driver's peripheral vision. Consequently, the variety of color and textures of complex, multi-species plantings is not appreciated by the viewer as information technology would be in residential or commercial applications. For ease of management, plant lists should be short and composed of species that take demonstrated an ability not just to survive but to thrive in the roadside environs. Many ornamental plants that exercise well in residential or commercial settings do not perform well in the stressful conditions of the right-of-way. Loftier winds, exhaust fumes, and intense sunlight and estrus make establishment hard for even the hardiest plants.
While some native plants are suitable for the roadside, the roadside is very different compared to native environments. Roadside soils are bailiwick to extremes of heat and cold due to the absenteeism of tall grasses or litter layers present in about native constitute communities. Understory trees such as Yaupon (Ilex decidua) that are bonny in a forest setting will generally not perform every bit well in the exposed weather of the roadside. Additionally, slopes that assure well-drained weather for roadbeds and structures atomic number 82 to hot dry soils in the summer. Many native plants will be able to accommodate over time to some of these harsh weather but the fact they are native does not indicate whatever less need for carefully planned establishment programs.
Plant option criteria deal with the following areas:
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- water requirements Ballast: #WFNTGPLC
- adjustability to soils and climates Anchor: #VNVUHPIN
- appropriate size and shape of plants Anchor: #TGWKSCUJ
- longevity Ballast: #DAYTOYDK
- insect and disease resistance Ballast: #XSUPSYRG
- baneful or invasive plants Anchor: #XLVTCMOV
- pruning
Water Requirements. TxDOT is mandated to adopt wise h2o-apply techniques associated with landscape developments. Plants selected for use on the right-of-way must be sufficiently hardy to maintain themselves without regular, supplemental irrigation once they have get established. The goal of roadside landscape irrigation is to let the plants to become established such that supplemental irrigation is no longer required. In most situations, irrigation systems that are iii to v years quondam volition not be repaired if damaged. Arrangement design should let for scaling back the organisation to completely manual operation for institute replacement or during times of astringent drought. (See Plant Irrigation.)
Adaptability to Soils and Climate: Plants must be adapted to the climate of the area and to the unique surroundings of the roadway. The roadway has been engineered to support a paved travel surface. Consequently, the soils are oft re-consolidated and compacted substrate materials. These soils are ordinarily droughty and ofttimes infertile. In determining the adaptability of a plant, consider also its preferred soil pH, drainage needs, and pollution tolerance. Plants sited close to swales or in low, poorly drained areas should be capable of thriving in wetter soils. Those planted on slopes or near the tops of embankments should exist able to withstand drought and high wind conditions.
Advisable Size and Shape of Plants. Plants selected should fit inside their intended location without impairing safety or maintenance access when their mature size is attained. Plants must not obscure any unyielding structure within the xxx-human foot clear-zone.
Longevity. Plants should exist long-lived for their plant blazon and purpose. In some cases this may exist a native plant species but this is not a prerequisite to the consideration of a particular plant.
Insect and Disease Resistance. Avert using plants that are known to attract and harbor dissentious insects that are not easily controlled. Examples of plants to be avoided include (but are non limited to):
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- euonymus (scale) Anchor: #BQECWECP
- photinia (aphids) Anchor: #EQNYRPGL
- non-native holly (aphids and scale)
Noxious or Invasive Plants. Do not use plants that are considered noxious or invasive. Examples of plants to exist avoided include (but are not limited to):
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- cottonwood Anchor: #NBUEIQQG
- chinese tallow Ballast: #HLVDWONE
- chinaberry Anchor: #RTSXDXAP
- hackberry
Pruning. Plants requiring frequent pruning to await or perform well should non be used in the roadway. Plants such equally wax myrtle, photinia, or sumac may be more appropriately used in naturalized areas where frequent maintenance is not intended and the plant is gratis to achieve its full, mature size. No constitute should be placed where pruning will be required in the future to maintain safe sight-distances.
Due to the open character of the roadway, plants are often exposed to loftier winds. Trees which are weak-wooded or that routinely generate excessive limb-fall such as pecan and mimosa can provide potential hazards to traffic or become projectiles during mowing operations. Plants that are susceptible to limb breakage should exist avoided. Plants that produce large or popular fruits are non suitable for the roadside since these may entice pedestrians into the roadway or generate projectiles. Examples of plants to be avoided include but are not limited to:
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- pomegranate Ballast: #IEKNVLDF
- persimmon Ballast: #UOEGLCBV
- bois d'arc Anchor: #KCWBCMBP
- fruiting plums Anchor: #ODXQIPGI
- pears Anchor: #JPDNYVLI
- pecan
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Constitute Container Sizes
Plant container sizes volition vary according to the type of plant and to the species. Shrubs will usually be nominal sizes of one to five gallons. Trees should more often than not be installed in sizes large enough to baby-sit against theft yet small enough to exist handled without the utilize of heavy equipment. Generally, xx-xxx gallon sizes see these requirements in about situations. It is recommended that big copse (greater than 3 in (75 mm)) be used very sparingly if at all. Experience has shown that larger trees establish slower and are more susceptible to transplant daze than smaller specimens.
Refer to Item 192, Tabular array 1A and 1B in the TxDOT Standard Specifications for Construction of Highways, Streets and Bridges for a listing of container dimensions and designations.
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Vandalism
The potential for vandalism and theft of materials within the correct-of-style is sometimes high. Projects that are well-nigh susceptible are those with portions of the site not visible from routine traffic or those which take structures like bridges or culverts that provide shelter in inclement weather. Irrigation systems near areas such every bit these should have no above ground parts and include lockable covers on valves to discourage vandalism by persons using the water for drinking or bathing.
Constitute theft is as well an occasional problem particularly if the project is nigh residential areas. In such cases, select found sizes that discourage theft and avert the use of small shrubs.
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Using Trees in the Roadway
The size of copse at time of planting should be based on budget, visibility of the plant to mower operators, and susceptibility to theft. Generally, pocket-size tree sizes less than two inches caliper are more susceptible to being stolen, peculiarly when the installation occurs almost a residential area. Large trees greater than 3 inches caliper are usually slower to constitute in the right-of-fashion and often exhibit some dieback within the offset two to iii years. In most cases the middle range of sizes, 2 - 3 inches caliper is a reasonable compromise for ease of installation, institution, visual bear upon, and costs.
In some cases, the use of large trees, greater than iii inches caliper, may exist desired for the immediate visual impact they provide. Other than this large trees should be used sparingly. History has shown that loss rates are higher with larger specimens, even container-grown materials, and the college costs associated with purchase and installation are often impractical, given the corporeality of correct-of-manner being planted.
It is of import to note that trees with mature caliper of iv inches or greater cannot be planted within clear zone.
Trees volition require weeding and this can add significantly to the cost of maintenance of the projection. The design should consider the culling maintenance practices available and brand estimates on the predictable maintenance costs for this item.
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Using Shrubs in the Roadway
Massed shrub plantings are those shrubs that are planted in groups or rows and where each is planted into individual planting pits (no area soil tilling) with the intention of creating a continuous shrub cover over the planted surface area. This method is almost often used for erosion control on slopes, filling areas that are difficult for mowers to access, and screening off-site areas (run across Figure 2-9). The preferred species for these applications are the larger shrub varieties. Avoid shrubs with leggy growth habits (ex. Photinia) since these invite weed and grass growth that is hard to access with mowing equipment. Species that carry their foliage shut to the footing surface are preferred since this helps reduce weed growth about their trunk and reduces the need for mitt weeding and the possibility of impairment due to cord trimmers or mowers.
Effigy two-9. Massed shrubs on slopes add visual involvement in addition to improving mowing efficiency in tight corners.
Bed plantings are those areas of tilled, prepared soil planted with varying plant types, usually shrubs. Beds should always be contained within borders deep enough and wide enough to foreclose grass and weed invasion by stolons or rhizomes (see Effigy two-10). A meaning portion of a bed is by and large open to weed invasion during the establishment period, necessitating frequent weeding activities either past hand weeding or with herbicides. Consequently, the maintenance costs for shrub beds can be a meaning office of the overall maintenance budget.
Figure 2-x. Bedded plants in turf areas require substantial edge protection confronting invasive grasses.
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Using Groundcovers and Seasonal Colour Plants
Traditional groundcover plant species such every bit Asian jasmine, honeysuckle, Virginia creeper, English or Algerian ivy, and similar species are often not suited to the constitute direction goals of TxDOT due to their general lack of hardiness, specialized maintenance needs, and susceptibility to invasion by weeds. Low-growing evergreen shrubs are a amend alternative for situations where groundcovers are desired. Refer to Figures ii-five and 2-6 for examples of groundcover settings.
The use of seasonal, ornamental plants (i.e.: almanac color) is discouraged inside the right-of-way due to the high costs of maintenance and replacement. Such plantings should not be included in projects that will be under country maintenance contracts.
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Plant Material Relationship to Structures
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- Signs: No plants with the potential of blocking a sign should exist placed in front end of the face of any sign (see Figures two-11 through two-14). Anchor: #TUGRDRYF
- Retaining and Noise Walls: Plants should not be placed any closer to a wall construction than half the expected mature spread of the plant. Anchor: #MGVHTWDL
- Elevated Roadways: Plants should not be placed where foliage may intrude to within 10 feet of the travel lane of elevated roadways and bridges (see Figures 2-fifteen). Ballast: #BQCQTPYV
- Tempest Water Structures: Copse placed almost drainage structures may inhibit mowing equipment and lead to excessive hand maintenance. Keep trees at least 20 feet from headwalls and culverts to permit mower access.
Figure 2-11. Plants must not exist placed where they may obstruct whatever sign.
Figure 2-12. Visibility within intersections is always a primary goal. Establish employ in intersection areas must exist limited to depression-growing varieties.
Figure 2-xiii. Approach ramps require long, unobstructed sightlines. Practice not place plants near merging lanes.
Figure two-14. Select and maintain plants at intersections that provide open up visibility in all directions.
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Planning and Blueprint for Mural Maintenance
The suitability of any development for Texas roadways will finally exist determined by its ability to be managed and maintained within the resource levels equally determined past TxDOT. All proposals for development will include estimates of the extent, duration, and costs of maintenance into the futurity. (Estimating procedures are provided in the following capacity of this set of guidelines.)
Routine Maintenance Activities. Maintenance activities of i sort or another are constantly taking identify within the correct-of-mode. These include but are not limited to litter pickup, mowing, trimming, construction inspections or repair, sign repair, guardrail repair, and herbicide application. Landscape development must exist undertaken so that access is provided for normal maintenance operations. Come across Figures 2-16 and 2-17 for design considerations related to maintenance activities. Improvements must avoid the creation of unsafe weather for motorists or maintenance personnel.
Effigy two-xv. Copse should not be placed where their mature height or spread will interfere with utilities or encroach on travel lanes.
Figure ii-sixteen. Allow aplenty room around drainage structures to facilitate maintenance.
Safety. Avoid situations that would require personnel and equipment to exist on the driving lane side of guardrails and concrete barriers or on the shoulders of high-speed, main-lane traffic. On frontage roads, allow a minimum of 3 anxiety clear space between the back of curb and any expanse to be maintained for maintenance personnel (and their equipment) to stand up well clear of moving traffic.
Effigy two-17. E'er provide paved setbacks well-nigh traffic lanes for the safety of maintenance crews.
Mowing. Mowing roadway vegetation is an of import maintenance activity. Landscape development projects must have into consideration the functional requirements of the operation to insure that condom and efficiency are not impaired. The consideration of mowing operations within a corridor must also recognize the relationship between fourth dimension and equipment. Mowing costs are calculated past the acre for each mowing event and can be significant over time. The rate per acre is a function of the estimated time required to mow an expanse that is determined past equipment size and obstructions nowadays. Areas that have no or few impediments can be mowed with larger equipment, thereby reducing time and lowering costs. Areas where access is express volition necessitate using smaller equipment, accept longer, and increase costs.
The width of the mowing equipment determines turning radius and maneuverability and is impacted past the spacing and arrangement of elements inside the site. In full general, the design should allow for flowing movements of equipment and avoid sharp turning operations. Avoid the use of isolated obstacles that would impede mowing operations. Consideration should be given to how the equipment will enter and exit the site and how and where turning operations will be required.
Figure two-xviii. Trees on steep slopes can impose dangerous turning motions on mowers and ofttimes lead to damage of soil-property grasses.
Weeding, Trimming, and Mowing. The virtually costly maintenance operations in mural development projects are weeding, trimming, and mowing. When designing plantings for the roadway, conscientious consideration should exist given to how these may minimize backlog maintenance requirements while improving the overall maintenance efficiency of the roadside (see Figures ii-10 and 2-xix).
Figure 2-xix. Concrete paving in hard-to-reach areas reduces maintenance costs and improves roadway appearance.
Specialized Maintenance Activities. It is important that proposed mural developments be manageable inside the resources capabilities of TxDOT. This includes anticipating the capabilities of the contractors responsible for executing maintenance contracts. In some cases, projects may exist maintained by public agencies outside TxDOT. In these instances, the design should be tailored to the maintenance capabilities of the municipality or civic system involved.
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Plant Irrigation
Irrigation of landscape plants is generally recommended both to protect the monetary investment of the project and to help insure the plants' healthy evolution. Turf irrigation is non appropriate for the right-of-way except in those situations where responsibleness for the maintenance and operation is causeless by other entities.
The atmospheric condition of the roadside determine the type of irrigation system suitable for use. Windy conditions tin accident sprayed water onto pavement surfaces, perhaps creating slick weather condition where the driver does not expect them. Therefore, baste or bubbler irrigation techniques are preferred over those that discharge water in the grade of sprays. In addition, keeping water on the desired target aids in water conservation.
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Irrigation System Types
Baste organization components may consist of barbed emitters in polyethylene tubing or in-line emitter tubing. Spaghetti tubing from multi-nozzle emitter heads should not be used due to ease of harm and numerous parts involved. Bubbler irrigation systems discharge water as a low pressure menstruum or as streams. Either of these may be appropriate depending on the blazon of plants and their spacing.
Irrigation systems should exist designed and then that no parts of the system are higher up ground in order to foreclose vandalism, unauthorized use and to minimize exposure to damage. Valves or controllers that cannot be located beneath footing should be secured in locked boxes. Brass valves or nozzles should non be used due to their historically high incidences of theft for their salvage value.
Large irrigation systems should consider the use of automatic, electronic controllers. The utilize of solar ability is permissible where costs brand electric service impractical. Where possible, equipment selection shall lucifer that of the systems already present on the roadside to create an economic system of maintenance. Small irrigation systems may be able to rely on manual functioning but the costs and unpredictability of manual functioning should exist considered. Truck irrigation is an option in isolated situations but unpredictable operators and damage to the site past the vehicles are of import bug.
All irrigation systems volition crave routine inspection and maintenance. This factor should exist considered in the development of long-term maintenance cost estimates.
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Designing for Weed Control in Ornamental Landscape Plantings
The most costly aspect of the management of ornamental plantings is weed control. The application of design techniques that limit weed invasion is the offset step towards reducing the overall cost of the projection and extending its life.
Cost-effective, long-term weed control in shrub plantings is dependent on the rapid development of salubrious plants. Therefore, intensive and timely procedures should be specified for the early stages of the project, peculiarly the 90-twenty-four hours establishment menses.
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Pattern Guidelines for Weed Control in Tree Plantings
Weeds at the bases of copse are cruddy and requite the advent of shoddy maintenance in add-on to inhibiting the development of the tree. The following guidelines are recommended practices for controlling weeds in tree plantings.
Soil Amendments. The preferred backfill for new copse is the native soil excavated from the planting pit. Where native soils are rocky or filled with large clods, add compost or other specified material to fill voids in the backfill.
Soil amendments are best practical to the upper few inches of the backfilled pit to improve oxygen availability to the surface roots of the tree. Studies have shown that the addition of soil amendments creates a soil texture very different from the surrounding soils. This texture departure leads to a wicking-away effect on water practical to the plant, resulting in a water stress condition. If soil amendments are added to the backfill, irrigation schedules should be adjusted based on observation of soil moisture in the planting pit.
Fertilizers.
- Anchor: #JKNOBJCU
- Use soil tests to make up one's mind fertilizer needs of new tree plantings. Anchor: #XOTRVEWM
- Utilize fertilizer to the surface or top two inches of the planting pit. Ballast: #IJHASPYR
- Apply a fertilizer drench in one case every 30 days during the ninety-day establishment period.
Weed Control. For command of annual weeds in new plantings, include a granular pre-emergent to the surface of the planting pit prior to mulch installation. For control of perennial weeds, specify liquid mail service-emergent herbicide as needed and include removal of weed residue.
For command of annual weeds in post-construction or existing plantings, specify water- soluble or granular pre-emergent applied to surface of mulch layers. Follow with mitt removal of weed rest.
For control of perennial weeds, specify liquid post-emergent as spot handling as needed. Follow with hand-removal of weed residual.
Mulch. Pine bawl mulches may be used on slopes less than 4:1. They are not recommended for slopes greater than 4:1 considering they are easily dislodged and will migrate to the lesser of the slope. When using pine bark mulches specify a particle size of one-half to one inch, with an installed depth of two inches, unless otherwise shown on the plans.
Hardwood mulches are suitable for all slopes since they tend to "knit" together and resist erosion. Specify a particle size not longer than 6 inches at an installed depth of ii inches, unless otherwise shown on the plans.
Irrigation. Conduct on-site field test to make up one's mind water infiltration rate to gear up minimum awarding per found.
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Design Guidelines for Weed Command in Beds and New Shrub Plantings
The goal of blueprint for weed control in shrub beds or mass plantings is to quickly institute a dense cover of leafage so weeds are not able to effectively compete. Plantings should be designed and then that at the end of ii complete growing seasons, the plants class a complete, continuous canopy. This goal places strict requirements on the selection of plants for landscape projects. The requirements for shrubs or ground covers are:
- Anchor: #IWYAGTSK
- The plant should hold its leafage all year (evergreen); deciduous plants allow invasion by many almanac weeds. Anchor: #DWXQCBEQ
- The plant foliage must be dumbo enough to completely shade the ground surface. Anchor: #UPLYBRBG
- The constitute should take a spreading growth habit rather than upright. Anchor: #ETKQATQV
- The top of the mature foliage should be at least 12 in.
The following items highlight the design alternatives to be considered for decision-making weeds in shrub plantings.
Bed Preparation. Specify a non-selective post-emergent herbicide to kill all vegetation and remove all existing sod to a depth of three inches. Specify weed-free replacement soil, or compost or other specified fabric.
Edgings. Beds should be edged with physical to preclude weed invasion from adjacent vegetation. The edging should be a minimum of 12 inches wide and thick enough to withstand the weight of mowing equipment. Modular materials, such as concrete pavers and fieldstone have joints that let weed invasion and should exist used sparingly. Steel edging is non recommended because this material cannot agree up to mowing equipment.
Soil Amendments. Organic soil amendments such as bark, tree clippings, etc. are recommended for most bed plantings if they have been thoroughly composted and this should be specified clearly, refer to current compost specification. Uncomposted material such as fresh sawdust or tree trimmings should never exist used.
Mulch. See mulch subsection for Design Guidelines for Weed Command in Tree Plantings.
Weed Barriers. Synthetic fabrics may be suitable for bed plantings but mulch on steep slopes could exist easily dislodged by water runoff. All fabrics should exist covered with appropriate mulch.
Weed Control. For control of annual weeds during 90-day institution period use granular pre-emergent to soil surface of planting pit prior to mulch installation.
For control of perennial weeds during 90-24-hour interval establishment period utilize liquid post-emergent spot treatment as needed. Follow with repeat application and specify follow-upwards for hand removal of weed remainder.
Irrigation. Beds should be designed for permanent irrigation. Drip or bubbler systems are recommended (see Establish Irrigation) and watering rates should exist set according to site conditions.
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Source: http://onlinemanuals.txdot.gov/txdotmanuals/lad/landscape_design.htm
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