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New Urbanism: Planting Standards

By Buck Abbey, ASLA, LASN associate editor for ordinances






Tree planting spaces recommended in the SmartCode are a minimum of four feet by four feet or a total of 16 square feet. This size space might be appropriate for small ornamental trees but is too small for larger trees.




The important place-maker is the code." --Vincent Scully, The New Urbanism, The Architecture of Community



This column has provided several stories over the last few months concerning the landscape design standards associated with New Urbanism and the SmartCode. New Urbanism communities conserve natural areas when appropriate and provide for the design of new civic spaces that include parks, greens, squares, plazas and playgrounds. Detailed landscape standards are also provided in the SmartCode for spaces closely associated with buildings. This is typical of most landscape codes.

New Urbanism Landscapes

Article 5 of the SmartCode ("SmartCode: A Comprehensive Form-Based Planning Ordinance" by Andr?s Duany) describes detailed landscape standards and provides design tables (1, 3C, 4A, 4B, 6, 7 and 9) that set technical standards for the design of small spaces associated with building site plans. (Ed. note: For Duany's complete article and tables, go to tndtownpaper.com/images/SmartCode6.5.pdf)

Table 1, for instance, identifies variations in planting based upon the six transect zones (T zones), which are central to new urbanism inspired design. A transect is a "geographical cross-section of a region used to reveal a sequence of environments," states Andr?s Duany in "Curbing Sprawl with a Code." He explains further: "For human environments, this cross-section can be used to identify a set of habitats that vary by their level and intensity of urban character, a continuum that ranges from rural to urban. In transect planning, this range of environments is the basis for organizing the components of the built world: building, lot, land use, street, and all of the other physical elements of the human habitat. One of the key concepts of transect planning is the idea of creating what are called immersive environments. Successful immersive environments are based, in part, on the selection and arrangement of all the components that together comprise a particular type of environment. Each environment, or transect zone, is comprised of elements that keep it true to its locational character. Through a complete understanding of the transect, planners are able to specify different urban intensities that look and feel appropriate to their locations."

In T1 zones landscape design is informal and naturalized. As T zones become more urbanized, landscaping becomes more formal and planting spaces become smaller and more compact. Limited planting spaces are available in the T6 urban core zone. Table 3C provides standards for the planting of public thoroughfares. Planting for circulation is broken down into a variety of passageways, including roads, boulevards, commercial streets and even avenues. Plantings vary from informal on low-intensity roads to formal streetscape plantings on avenues and in commercial districts. No planting standards are given for alleys, bike trails, paths or transit routes, all essential passage ways.

Tables 4A and 4B set forth planting standards for public frontages commonly called street tree planting in traditional zoning ordinances. Planting in this zone is primarily trees, arranged in a formal manner in which trees are equally spaced within the more densely developed T5 and T6 zones and more informally planted within the T3 and T4 zoning district. Public frontages are generally not planted within T1 and T2 zones due to their rural character. It is assumed that local government provides these plantings since they are included on public land.

Table 4B gives specific design standards, including dimensions for curbs, walkways, planters, swales and landscape. These are the elements of public frontage.

Table 6 sets forth standards for public tree plantings. Six typical tree forms are given for use in the planting design of public spaces. They include tree species that have defined shapes such as vase, umbrella, pyramid, ball, oval and palm-like. Landscape architects presumably specify the correct species by botanical name to achieve these predicated forms. The code requires that trees should be selected to provide high canopies that will not block views into commercial shop fronts. They must also be tall enough to allow public utility lines to pass under the crown. Selected species should be durable, hardy and able to withstand the severe growing conditions found in tight urban spaces.

Tree planting spaces recommended in the code are a minimum of four feet by four feet or a total of 16 square feet. This size space might be appropriate for small ornamental trees but is too small for larger trees. This space is not large enough for the use of species noted in Table 4B and recommended as street trees. Within traditional zoning ordinances, in contrast, planting spaces for Class A trees are generally a minimum 100 square feet to allow proper rootball growth and crown development.

Design Table 6 is horticulturally problematic and assumes that all street trees should be large native shade trees.

Private frontages are equivalent to street yard planting areas in traditional zoning ordinances whose purpose is to improve the view from the street. Table 7 (private frontages) sets forth several variations of outdoor space that can be designed as common yards, fenced enclosures or paved forecourts depending upon the T zone.

Within the technical language of the SmartCode, private frontage plantings seem to be used as decorative planting space to enhance building design and the edge of the public street. This street frontage is used to establish the urban character of a center city neighborhood. There is generally no private frontage landscaping within the city center or T6 zone. The street wall of the building, a gallery, arcade, shop awning or stoop is pushed to the property line and is used to establish the interface between the private zone and the public realm. This leaves no space for landscaping.

The last design table of concern to landscape architects is Design Table 9 that sets forth the building disposition standards of the principal structure and all pervious plantable areas that might surround it. There are five typical building footprints in this code that can be planted, depending on the T zone. They include edgeyards, sideyards, rearyards, courtyards and specialized building typologies, all based upon the relationship of building to property line. Sadly, there are no specific landscape design standards for these smaller private spaces associated with buildings as would be found within traditional landscape codes.






Noticeably missing from the SmartCode are site design standards for parking lots. Andr?s Duany notes, however: "Through a complete understanding of the transect, planners are able to specify different urban intensities that look and feel appropriate to their locations."


Further Development Needed

New urbanism shows promise for making urban developments green. The landscape planting aspects of new urbanism are critical factors of community design, but they need refinement. Landscape standards must be allowed to be more environmentally useful and must recognize plants as something beyond mere urban decoration. Specialty gardens and use of outside space for instance are not mentioned in the SmartCode. Noticeably missing from this code are site design standards for parking lots, site service areas, offsite screening and the civic spaces noted in Table 13. More attention must be given in the SmartCode to irrigation, stormwater management and the detailing of streetscape amenities. With time and attention to detail, the landscape standards of the SmartCode can be elevated to refined proscriptive and prescriptive standards set forth in traditional community landscape codes as found in communities such as Austin, Chapel Hill, Atlanta, Seattle and San Diego.

What is excellent about the SmartCode is that landscaping is considered as an important element of new urbanism.






Transect Zones

The six transect zones (T zones) are central to new urbanism inspired design. As T zones become more urbanized, landscaping becomes more formal and planting spaces become smaller and more compact. The T zones elements are Land Uses, Buildings, Private Frontages, Public Frontages, Thoroughfares and Open Spaces. Here we list only Land Uses and Public Frontages criteria.

Transect Zone I

  • Land Uses: Natural preserve, recreation and camping.
  • Public Frontages: Swales and naturalistic planting,
    bike trails.

Transect Zone 2

  • Land Uses: Natural reserve, agriculture, recreation
    and camping.
  • Public Frontages: Swales and naturalistic planting,
    bike trails.

Transect Zone 3

  • Land Uses: Low-density residential and home occupations.
  • Public Frontages: Open swales, some flat curbs,
    bike lanes and naturalistic tree planting.

Transect Zone 4

  • Land Uses: Medium density residential and home occupations; limited commercial and lodging.
  • Public Frontages: Raised curbs, narrow sidewalks, bike lanes, continuous planters, street trees in allee.

Transect Zone 5

  • Land Uses: Medium intensity residential and commercial: retail, offices, lodging, civic buildings.
  • Public Frontages: Raised curbs, wide sidewalks, bike routes, continuous or discontinuous planters, street trees in allee.

Transect Zone 6

  • Land Uses: High-intensity residential and commercial: retail and offices, lodging, civic buildings.
  • Public Frontages: Raised curbs, wide sidewalks, bike routes, discontinuous planters, street trees in allee.






D.G. "Buck" Abbey, Associate Professor of Landscape Architecture at Louisiana State University, is LASN's Associate Editor for Ordinances.




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October 23, 2019, 10:29 pm PDT

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