Landscape Design and Planting Criteria

It is essential to note all the existing conditions on an accurate base map when doing the site inventory Figure 2. Utilities such as power lines, septic tanks, underground utilities and roof overhangs determine plant location. Use a surveyor's plat of your property for the boundaries and location of your home. Measure and note on the survey other structures and hardscape such as patios, driveways, or sidewalks. It is very important to hire a surveyor if you do not have a plat; guessing the location of boundaries can be a costly mistake.

The users are typically you, your family, the family pets, and visitors, and each have their own needs. There are five things to consider: It is very important to consider how you currently use the yard. For example-which entry is used by whom, where do the kids play and where does the dog usually run? Figure 3 Thinking about how you currently use the yard, and how you want to use the yard in the future Figure 4 , determines the need to re-organize old spaces into new spaces and amenities.

It is also important to remember the vehicles used by your family; driveways and parking are space intensive. Budget concerns include the materials, initial installation costs and the on-going maintenance costs. Determine the time and money you are willing to put into maintaining the plants and hardscape-be realistic about your intentions and ability. There are many different landscape design themes- from simple to complex, but it is helpful to choose one to guide your plant and material selection.

Think of a theme as the inspiration for your garden. Many people find it helpful to look in gardening magazines and books for ideas. This is a good start, but be aware that the gardens in the photos were picked because they are outstanding examples. Look at the photos with a critical eye to gather ideas that you can adapt to your passion level, your budget and your site. Before choosing a theme it is important to look at the surrounding views of your property.

Decide if you want to open your yard, close your yard, or a little of both, to these views. In other words, do you want the garden to enclose the space around you and relate mostly to the house, or do you want the garden to open views and look outward, relating to the surroundings? This will give you a starting point to think about a theme. Care should be taken to choose appropriate themes for your yard based on the architecture, the type of neighborhood, the topography, and the regional landscapes.

This is called "sense of place", which means it fits with the surroundings. There are both form themes and style themes. Every garden should have a form theme, but not all gardens have a style theme. In fact, many residential gardens have no particular style except to blend with the house by repeating details from the architecture such as materials, color, and form. All gardens, however, should use a form theme to create spaces for activities.

In a form theme the organization and shape of the spaces in the yard is based either on the shape of the house, the shape of the areas between the house and the property boundaries, or a favorite shape of the homeowner. The form theme determines the shape and organization the layout of the spaces and the links between them. Common themes include geometric, such as a circle, square, and rectangle; or naturalistic such as irregular organic edge or curvilinear meandering lines Figure 5. Form themes are sometimes combined; geometric shapes are used for the hardscape and naturalistic shapes for the plantings.

For example, plant bedlines are often curvilinear while the hardscape is square in form. Style themes are most often related to the architecture and they often simplify the design of a residential yard because materials and form are to some extent pre-determined.

Landscape design criteria.

Many style themes today are a contemporary version of traditional garden designs. Architecture is usually the primary source of a theme, but themes can also represent a time, a culture, a place, or a feeling, such as serenity or calmness. The advantage to using a traditional style theme is the established set of forms and elements have historically worked well together and endured the test of time. Because architectural styles typically fall into a formal or informal category, the landscape theme tends to be either formal or informal Figure 6.

Formal architectural and garden styles that can be used for inspiration include French, Spanish, Italian, and Middle Eastern. Less formal designs include Oriental, English, and American. Style themes can also apply to the planting plan and may include tropical, desert, meadow, woodland, marsh, or coastal plantings. Themes can be as simple as a color mix or plants with a distinct character- such as grasses-used repeatedly in the composition.

The yard is an extension of the home where a variety of activities take place. A yard can generally be divided into three areas: The location of activity areas depends primarily on the type of area, the size of space needed, the type of activity, and the desired proximity to other activities and structures. Perhaps the most important spatial concept for successful garden design is the creation of outdoor rooms in the yard.

These spaces are often separated through the use of plant beds, sod areas, trees, planters, garden walls, arbors, level changes, and paved surfaces Figure 7. The features are used to enclose or define the spaces and give them a room-like feel. For psychological comfort, creating spaces that are of human scale is important because most people prefer to be in places that feel protected and sheltering, rather than open and exposed. The outside wall of the house often serves as the first wall or starting point of an outdoor room. Incompatible uses should be separated, and related activities, such as cooking and dining, should be put together to make the yard more efficient and enjoyable.

When using hardscape to create spaces, use construction material similar to that used in the house for continuity from the house into the garden. Pedestrian circulation in the landscape should move people through the yard and provide organizational structure.

Outdoor rooms are typically linked by pathways, steps, and walkways, or openings with gates or arbors that encourage exploration and use of the entire yard Figure 8. These spaces can also be linked by visual features such as a creek bed wet or dry that meanders through or beside several spaces, or a garden wall that begins at a patio, moves along a turf area and ends along a planted area. Using similar hardscape features and repeating plants pulls the eye around the garden.


Reusing construction materials will reduce the environmental impact of using new materials and keep old materials out of the waste stream. Shrubs will usually be nominal sizes of one to five gallons. Establishing focal points Crafting views Incorporating personal touches And more! Search for the word or phrase:. This is a good start, but be aware that the gardens in the photos were picked because they are outstanding examples.

Important points along the way can be emphasized with plantings or features that draw attention and encourage movement in a particular direction. Moving along the path takes a person from one area to the next and allows the user to have a variety of experiences. In an informal garden the curves and bends of the path should partially conceal what lies ahead. This provides a sense of mystery that promotes exploration and discovery of the landscape. From a design perspective, plant materials have three major functions in the landscape: Aesthetically, plants create a visually pleasant environment and structurally plants organize and define spaces.

Low and moderate water use plants can be mixed but the entire hydrozone will be classified as moderate water use for MAWA calculations. High water use plants shall not be mixed with low or moderate water use plants. Plants shall be selected appropriately based upon their adaptability to the climate, geologic, and topographical conditions of the site. Protection and preservation of existing native species and natural areas is encouraged. The planting of appropriate trees is encouraged.

The Minimal Use of Turf. Turf areas shall be used wisely in response to functional needs and shall not exceed the MAWA. Where turf is installed, the use of warm season turf is strongly encouraged. Turf is not allowed on slopes greater than twenty-five percent where the toe of the slope is adjacent to an impermeable hardscape and where twenty-five percent means one foot of vertical elevation change for every four feet of horizontal length. The establishment of naturalized areas in the roadway will often entail specialized management techniques and scheduling that may require special specifications and contracting procedures.

These needs should be carefully considered in determining the appropriate use and design of these features. Plants can be an important addition to the right-of-way as an aesthetic enhancement that blends highway structures with the surrounding environment.

Section 4: Landscape Design

Figures through show examples of effective planting design. The proper use of plants can help make roadways a positive element in the visual fabric 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 use of plants in the right-of-way must always be considered in the context of the important role of safe, maintainable transportation corridors. Median plantings can add color and visual separation between driving lanes.

Bedded plantings in islands can add interest and variety. Height restrictions on plants in these areas are critical. Pedestrian-ways are often good locations for ornamental plantings. Plants are effective for visually softening tall retaining walls or noise walls. TxDOT is required to use regionally appropriate plants in highway right of way beautification projects.

Plants for the right-of-way must also be selected based on their anticipated maintenance needs and their adaptability to the roadside environment. The placement of plant material in the roadway is of critical importance because of its potential effect on driver safety.

Plant placement will be discussed in a separate section see Plant Material Relationship to Structures subsection. Consequently, the variety of color and textures of complex, multi-species plantings is not appreciated by the viewer as it would be in residential or commercial applications. For ease of management, plant lists should be short and composed of species that have demonstrated an ability not just to survive but to thrive in the roadside environment. Many ornamental plants that do well in residential or commercial settings do not perform well in the stressful conditions of the right-of-way.

High winds, exhaust fumes, and intense sunlight and heat make establishment difficult 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 subject to extremes of heat and cold due to the absence of tall grasses or litter layers present in most native plant communities.

Understory trees such as Yaupon Ilex decidua that are attractive in a forest setting will generally not perform as well in the exposed conditions of the roadside. Additionally, slopes that assure well-drained conditions for roadbeds and structures lead to hot dry soils in the summer. Many native plants will be able to adapt over time to some of these harsh conditions but the fact they are native does not indicate any less need for carefully planned establishment programs.

TxDOT is mandated to adopt wise water-use techniques associated with landscape developments.

Landscape Design Principles for Residential Gardens

Plants selected for use on the right-of-way must be sufficiently hardy to maintain themselves without regular, supplemental irrigation once they have become established. The goal of roadside landscape irrigation is to allow the plants to become established such that supplemental irrigation is no longer required. In most situations, irrigation systems that are three to five years old will not be repaired if damaged. System design should allow for scaling back the system to completely manual operation for plant replacement or during times of severe drought. Adaptability to Soils and Climate: Plants must be adapted to the climate of the area and to the unique environment of the roadway.

The roadway has been engineered to support a paved travel surface. Consequently, the soils are often re-consolidated and compacted substrate materials. These soils are usually droughty and often 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 be able to withstand drought and high wind conditions.

Principles of Landscape Design

Appropriate Size and Shape of Plants. Plants selected should fit within their intended location without impairing safety or maintenance access when their mature size is attained. Plants must not obscure any unyielding structure within the foot clear-zone. Plants should be long-lived for their plant type and purpose. In some cases this may be a native plant species but this is not a prerequisite to the consideration of a particular plant. Insect and Disease Resistance. Avoid using plants that are known to attract and harbor damaging insects that are not easily controlled.

Examples of plants to be avoided include but are not limited to:. Noxious or Invasive Plants. Do not use plants that are considered noxious or invasive. Plants requiring frequent pruning to look or perform well should not be used in the roadway. Plants such as wax myrtle, photinia, or sumac may be more appropriately used in naturalized areas where frequent maintenance is not intended and the plant is free to attain its full, mature size.

No plant 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 high 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 be avoided. Plants that produce large or popular fruits are not suitable for the roadside since these may entice pedestrians into the roadway or generate projectiles.

Plant container sizes will vary according to the type of plant and to the species. Shrubs will usually be nominal sizes of one to five gallons. Trees should generally be installed in sizes large enough to guard against theft yet small enough to be handled without the use of heavy equipment. Generally, gallon sizes meet these requirements in most situations. It is recommended that large trees 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 shock than smaller specimens. The potential for vandalism and theft of materials within the right-of-way is sometimes high.

Projects that are most susceptible are those with portions of the site not visible from routine traffic or those which have structures like bridges or culverts that provide shelter in inclement weather. Irrigation systems near areas such as 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. Plant theft is also an occasional problem particularly if the project is near residential areas.

In such cases, select plant sizes that discourage theft and avoid the use of small shrubs. The size of trees at time of planting should be based on budget, visibility of the plant to mower operators, and susceptibility to theft. Generally, small tree sizes less than 2 inches caliper are more susceptible to being stolen, particularly when the installation occurs near a residential area.

Large trees greater than 3 inches caliper are usually slower to establish in the right-of-way and often exhibit some dieback within the first two to three years. In most cases the middle range of sizes, 2 - 3 inches caliper is a reasonable compromise for ease of installation, establishment, visual impact, and costs. In some cases, the use of large trees, greater than 3 inches caliper, may be 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 higher costs associated with purchase and installation are often impractical, given the amount of right-of-way being planted.

It is important to note that trees with mature caliper of 4 inches or greater cannot be planted within clear zone. Trees will require weeding and this can add significantly to the cost of maintenance of the project. The design should consider the alternative maintenance practices available and make estimates on the anticipated maintenance costs for this item. 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 area.

This method is most frequently used for erosion control on slopes, filling areas that are difficult for mowers to access, and screening off-site areas see Figure