Landscape Design Criteria

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4.0 Introduction to Landscape Design Standards

4.1 Statement of Intent

The purpose of the following landscape standards is to provide supplemental requirements and criteria to the latest version of the City of Thornton Development Landscape Code and Standards and Specifications and to organize a framework in which the following goals are met.

  • Create a landscape theme for Larkridge that recognizes Thornton's agricultural history and reflects Thornton's natural environment in the cultivated landscape.
  • Insure consistency of design and materials throughout the site.
  • Provide site orientation, direction, connection, a sense of scale, and a feeling of security for users.
  • Enhance commercial and retail profitability.
  • Create an aesthetically pleasing environment.
  • Institute water-wise landscape principles and management techniques.
  • Guide future Larkridge landscape design and approvals process.

These standards and guidelines will insure that quality landscaping will be integrated throughout the project during the development review process.

4.2 Landscape Objectives

Consideration shall be given to plant material types, growth rates, and canopy sizes in relationship to building location, signs, site lines, site utilities, sight triangles, view corridors, and parking. A variety of plant materials shall be incorporated into the project including indigenous drought-tolerant vegetation, flowering trees and shrubs, evergreen trees, accent plantings, and ground covers. Evergreen, deciduous trees and shrubs, flowering ornamental trees, grasses, and groundcovers will be used in combination to provide year around seasonal interest and layering while maintaining the functional requirements.

  • Emphasize clusters of trees and shrubs in natural settings.
  • Feature wide bands of shrubs to suggest drainage ways and irrigation ditches with expanses of ornamental and turf grasses to mimic prairie.
  • Establish view corridors to the Front Range and the plains.

4.3 Landscape Concepts

  • Reserve the richness of plant palette and hardscape materials for pedestrian entrance areas, public gathering spaces and retail front door areas.
  • Shade trees in grates or built trellis structures provide a canopy within paved areas.
  • Raised planters, pots of seasonal color and other hardscape accents create 'topography' and pedestrian seating areas and delineate the boundary of front door entrance areas.
  • Water features draw pedestrians to public gathering spaces.
  • Identify outside seating areas and view corridors.
  • Plant similar clusters of large scale plant material to anchor and identify the built environment.
  • Create a hierarchy of vehicle and pedestrian entry areas with a hierarchy of monumentation and plant material selection.
  • Masses of evergreen trees and groups of deciduous trees with massed shrubs and wide areas of ornamental and turf grasses guide views to buildings, provide appropriate scale to buffer uses and establish foreground to screen or highlight building architecture and function.

5.0 Landscape Design Standards

5.1 Common Area Landscaping

The following landscape requirements shall be applicable for all landscape common areas.

a)    Common area landscaping shall have a minimum of one Tree Equivalent (TE) for every 300 square feet of area required to be landscaped.

b)    Reference the latest versions of the COT Development Landscape Code and Standards & Specifications for minimum requirements and criteria.

c)     A maximum of 50% of the total landscape area of each property may be planted with approved turf.

5.2 Public Rights-of-Way

The following additional landscape requirements shall be applicable for all areas within public rights-of-way.

     a)  A minimum of 1.5 Tree Equivalents (TE) shall be required for each 50 lineal feet.

     b)      Views into parking lots shall be screened from all public and private right of ways.

     c)  Plant materials must be located such that a minimum two-foot clear zone behind the back of curb allows for car bumper overhang unless curb stops are utilized.

d)    Shrubs shall be massed in order to strengthen street edges and buffer parking lots.

e)    Medians in public rights-of-way shall be landscaped per COT Development Landscape Code or as approved in the Development Permit process.

5.3 Parking Lot Islands

The following additional landscape requirements shall be applicable for all landscaped parking lot islands.

a)    Plant materials must be located such that a minimum two-foot clear zone behind the back of curb allows for car bumper overhang unless curb stops are utilized.

b)    Shrubs shall be massed in order to strengthen street edges and buffer parking lots.

c)    At 18' and wider Islands, a 3' wide band of 3" to 6" diameter cobble mulch over filter fabric shall be provided behind the curb. Top of cobble shall not be higher than the adjacent top of curb. All cobble shall be hand laid with flat sides down. Interior to the cobble mulch shall be Fir Fiber wood mulch.

d)    At 9' and up to 18' wide Islands, a 2' wide band of 3" to 6" diameter cobble mulch over filter fabric shall be provided behind the curb. Top of cobble shall not be higher than adjacent top of curb. All cobble shall be hand laid with flat sides down. Interior to the cobble mulch shall be Fir Fiber wood mulch.

e)    Parking lot islands in front of all buildings shall be a minimum 18 feet wide and 18 feet long and contain a minimum of 3 TE per island or as approved in the Development Permit process.

5.4 Building Perimeter and Pad Site Foundations

The following additional landscape standards are applicable for commercial retail, inline tenant space, and pad site developments.

a)  Building perimeter landscaping shall provide layering and visual interest during all four seasons and shall include a combination of decorative planted pots, shade trees in tree grates, raised planters or pad site foundation planting beds. To provide visual interest, plants shall be selected from a variety of plant categories. The major categories are:

.       Deciduous flowering and evergreen shrubs

.       Multi-stemmed and/or single trunk ornamental trees and shrubs

.       Annuals and perennial flowering species

.       Woody ground covers

.       Shade trees

     b)  Front door building perimeter areas consisting of hardscape between the building and the back of curb shall be planted with a minimum of 1 TE every 50 lineal feet of building perimeter as shade trees in grates, permanent planters, decorative planted pots or combination thereof.

c)  Trees located in pavement areas shall be planted in tree grates a minimum of 6' in diameter.

d)    Permanent decorative planted pots shall be a minimum of two-foot tall.

e)    Planters that will be located in pavement areas shall be a minimum of 4' wide and 18" high. Planter areas shall be located to strengthen pedestrian circulation, provide pedestrian refuge areas and transition grade.

f)     Building perimeter landscape design shall be coordinated with building construction documents in order to coordinate with doors, windows, signs, utilities, ramps, light poles and other features.

g)    Building perimeter landscape areas not covered in hardscape shall meet the common area landscaping requirement of 1 TE every 300 s.f.

h)  Major anchor tenants with specific requirements for no landscaping in front of their building may locate the building perimeter landscape requirements on the sides and rear of the building.

5.5 Service Area, Loading Dock & Utility Device Screening

     a)  Service, loading and utility areas shall be screened by fences, walls, landscaping, berms, or any combination thereof.

     b)  Planted areas must meet the common area landscaping requirement of 1 TE every 300 s.f.

c)  75% of the required landscaping must be evergreen.

     d)  Service, loading, and utility areas visible from residential areas shall be screened with a wall, berm, trellising or combination, in addition to landscape requirements.

     e)  Service and loading areas shall be landscaped with upgraded landscape materials. See Landscape Hierarchy Map for landscape upgrade areas.

5.6 Detention, Retention, and Water Quality Ponds

Detention, retention and water quality ponds shall be integrated physically, functionally, and aesthetically into the adjacent landscape design. Vegetated slopes shall not exceed 4:1 and all pond turf areas shall be properly drained. Water quality enhancement areas within the bottom of the pond shall be planted with vegetation that is appropriate with the presence of saturated soils.

a)    Pond depth should be limited to not more than ten feet. Pond grading should be designed to accommodate access for maintenance equipment. Rock-scaped or riprap slopes are prohibited except when necessary for erosion control and when approved by the City of Thornton. Ponds shall be designed with natural sides and bottoms and shrub beds adjacent to the top for transition to traditional, cultivated landscapes. Wetland plantings in low spots will be encouraged.

b)  Additional landscaped requirements for areas surrounding Detention, Retention, and Water Quality Ponds are as follows:

.       The area within the tract surrounding the pond(s) shall be planted with a minimum of 1 TE/3000 square feet of tract area.

.       All natural seed areas shall be watered by a permanent automatic irrigation system.

5.7 Seeding of Future Development Areas

All future phased development areas disturbed during construction shall be seeded and stabilized to prevent wind and water erosion for the time the site remains without development. Temporary irrigation to establish seeded areas is required.

5.8 Plant Material List

Landscaping for the development shall include a variety of appropriate water-wise plant material that reflect a mix of canopy, understory, groundcover and turf that are hydrozone compatible and are chosen from the Larkridge Plant List or as approved in the Development Permit process.

5.9 Plant Material Standards & Upgrades

The location of plant material standards and upgrades is illustrated on the Landscape Hierarchy Map. Upgraded plant material sizes shall not receive additional credit toward the TE requirement, unless otherwise approved during the Development Permit process.

a)    Plant material for all landscape areas identified as Service Areas, Loading Docks, and Utility Device areas (blue) shall be installed in the following minimum sizes:

.       Deciduous and Ornamental trees - B&B, 3" caliper or 8' height clump.

.       Evergreen Trees - B&B, 8' to 12' height

.       Deciduous and evergreen shrubs - #5 container

.       50% of evergreen trees to have 12' height minimum

.       75% of all trees to be evergreen

     b)  Plant material for all landscape areas identified as Upgraded Landscape Areas (red) shall be installed in the following minimum sizes:

.       Deciduous and Ornamental trees - B&B, 3" caliper or 8' height clump

.       Evergreen Trees - B&B, 8' to 12' height

.       Groundcover - #1 container

.       Deciduous and evergreen shrubs - #5 container

.       50% of evergreen trees to have 12' height minimum

.       50% of all trees to be evergreen

c)  Plant material for all other landscape areas shall be installed in the minimum sizes established in COT Development Landscape Code and as located on the Landscape Hierarchy Map.

5.10 Organic and Inorganic Mulches and Landscape Materials

The following mulches shall be used as described below:

a)    Perennial, groundcover and ornamental grass shrub beds shall include 3" depth Fir Fiber wood mulch without filter fabric. Re-apply wood mulch as necessary due to settlement.

b)    Landscape parking lot islands shall include a band of 3" to 6" diameter tan colored cobble mulch behind the curb over filter fabric. Cobble mulch shall be keyed-in with brown breeze crusher fines. Interior to the cobble mulch shall be 3" depth Fir Fiber wood mulch.

c)    Remaining planting beds shall include 1-1/2" diameter tan colored crushed river rock mulch with or without filter fabric, Fir Fiber wood mulch with or without filter fabric, or crusher fines as approved in the Development Permit process.

d)    Mulches shall match development type and samples shall be provided to Owner's Landscape Architect for review and approval prior to installation.

5.11 Organic Soil Amendments

All newly landscaped areas shall be amended with soil amendment, the amount and type of amendment based on representative site soil analysis. Soil amendment shall be incorporated a minimum of 6 inches deep and include the following:

a)    Soil Amendment rate: Minimum 4 cubic yards per 1000 s.f.

b)    Soil Amendment shall meet the following requirements:

.       Organic matter content: 30 to 50% (dry matter basis)

.       PH range: less than 7.5

.       Ammonia nitrogen: Max. 500 ppm

.       Salt content: max. 3.0 mmhos over 25c

.       Carbon / nitrogen ratio: 15-25

5.12 Drought Tolerant Turf Grass

All new landscape turf areas shall provide the following:

a)    100% 'Pure Gold' Tall Fescue (or approved equal) sod. ('Pure Gold' Tall Fescue is designated as a low water-demand sod and shall be zoned separately from different water-demand plant material).

b)    Legacy Buffalo Grass sod, plugs, or approved equal may be used as an ornamental grass substitution for particular areas of landscape turf.

5.13 Landscape Design Requirements

Tree diversity requirements shall be meet as follows: 10-19 trees (no more that 50% of any one species), 20 and over trees (no more than 33% of any one species).

5.14 Irrigation Design Requirements

a)    Trees in turf areas shall receive supplemental irrigation with drip irrigation on a separate zone.

b)    Low water-demand turf areas shall be zoned separately from different water-demand plant material areas.

Irrigation design and installation shall conform to requirements and criteria of the latest version of the City of Thornton Standards and Specifications or as approved in the Development Permit process.

5.15 Landscape Maintenance

All landscaped areas shall be maintained in a neat, clean, and healthy condition and include the following:

a)    Mowing and fertilizing of Pure Gold Tall Fescue lawns:

.       Weekly mow all lawn areas during the warm seasons to a height of 2"-3½" .

.       Provide fertilizer applications in the spring and fall. Pure Gold Tall Fescue requires low to medium nitrogen application with 2-4 lbs. actual nitrogen per year.

b)    Pruning:

.     Follow the American Nurseryman's Association pruning standards and procedures.

.     Immediately remove all dead or dying branches and stems.

.     Tree branches shall be removed where they conflict with pedestrian or vehicular circulation, traffic signs, etc..

.     Removal of evergreen tree under-story branches is not recommended.

.     Perennials and ornamental grass shall be cut back in the spring.

.     Formal 'ball type' pruning of shrubs is discouraged.

c)    Winter watering & deep root feeding:

.       Provide winter watering of trees and shrubs up to 2 times a month, as necessary.

.       Provide deep root feeding of trees in the spring, as necessary.

d)    Other:

.       Dead plant materials shall be removed and replaced with originally specified and approved materials, per the COT Development Code.

.       Provide regular removal of trash and other debris throughout the site.

.       Trees shall be regularly inspected and pre-treated for diseases.

.       Regular removal of snow and ice at private roads, parking lots, and pedestrian access routes shall be provided.

6.0 Landscape Appendix

6.1 Landscape Hierarchy Map

Landscape Hierarchy Map

6.2 Larkridge Approved Plant Material List

Download ZIP file with Plant Materials Lists