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Planting Details and Specifications - ISA
10.103 Acceptable Plant Material
(a) No artificial plant materials may be used to satisfy the requirements of this article.
(b) In satisfying the requirements of this article, the use of high-quality, hardy, and drought-tolerant plant materials is recommended and encouraged. (Ord. Nos. 22053; 25155)
- Encourages the use of native plant species.
- Notes that palm trees may not be used to satisfy the requirements of Article X.
- The building official shall have the authority to require plant species substitutions to a landscape plan if scheduled plants are deemed invasive.
- Synthetic turf may not be used to satisfy the requirements of Article X, and may not be used under the critical root zone of a protected tree without the approval of the building official.
- Discussion: The sensitivity of palm trees was well demonstrated across the region with the winter blast that fell on us Super Bowl week. As it had been some time since we had experienced a cold at the scale of the winter of 2011, the concerns of planting palms in North Texas seemed by some to be unwarranted. Nature teaches us well - if we listen. The UFAC recommends writing 10.103(b) to state "the use of high-quality, winter-hardy, and heat and drought tolerant plant materials' be recommended and encouraged." The current ordinance does not discuss details of ground cover except for around landscape areas. Synthetic turf can be manufactured and installed through different means and the primary concern for its installation is for tree root protection in areas where the sub-base may not allow for water and air infiltration, and the synthetic turf may artificially increase temperatures of the soil surrounding the roots. Further research on these turfs is needed.
Understanding Synthetic Grass Systems (ATurf - presented for educational purposes.)
Introduction to Cold-Hardy Tropicals For Virginia Landscapes (Virginia Cooperative Extension) -No, it's not Texas, but has a similar - if not cooler - climate. This is a good general resource for information on placing tropical exotics in a temperate environment.
Palm, California Fan
Common Name: California Washingtonia
Washingtonia filifera
Tree Size: Large
Leaf Type: Evergreen
Comments:
Commonly available palm from California or Florida nurseries.
Palm, Texas Sabal
Common Name: Texas Sabal Palm
Sabal texana
Tree Size: Medium
Leaf Type: Evergreen
Comments:
Only palm tree native to Texas; cold-tolerant; can be difficult to find nursery stock.
Palm, Windmill
Common Name: Windmill Palm
Trachycarpus fortunei
Tree Size: Small
Leaf Type: Evergreen
Comments:
A small palm for use in small spaces, or close to the shore.
Selected palm trees in the Texas Tree Planting Guide (Texas Forest Service).
10.104 Soil Planting Requirements
(a) Planting areas in general must have the following soil depths and dimensions:
(1) For each large shrub or small tree installation, a minimum of 24 inches of soil depth and 16 square feet of surface area (total of 32 cubic feet).
(2) For each large tree installation, a minimum of 36 inches of soil depth and 25 square feet of surface area (total of 75 cubic feet).
(b) Planting areas located above underground buildings or structures must have the following soil depths and dimensions:
(1) For each large shrub or small tree installation, a minimum of 30 inches of soil depth and 25 square feet of surface area (total of 62.5 cubic feet).
(2) For each large tree installation, a minimum of 40 inches of soil depth and 36 square feet of surface area (total of 120 cubic feet).
(c) The building official may waive the minimum planting area requirements if a landscape architect certifies that the proposed alternative soil depths and dimensions are sufficient to support the healthy and vigorous growth of the plant materials affected. (Ord. Nos. 22053; 25155)
- Planting areas for small trees require a minimum of 64 square feet.
- Planting areas for large trees require a minimum of 180 square feet.
- Minimum spacing for trees is specified in the Technical Manual. The building official may approve alternative spacing.
- Discussion: The terminology of the code should change to demonstrate that the soil planting area can expand under the built infrastructure. Through various
technologies, the planting area can expand beyond the traditional 5' x 5' planting holes through a multi-use substructure that allows for continual root growth. Expanded planting area can be at grade or below the infrastructure. Understanding how tree roots grow in an urban environment is critical to making sound planning decisions for long-term tree growth. The difficulty of applying minimum soil planting requirements is that trees are ALWAYS forced to compromise to our demands. When the trees are planted in large open spaces, they have a greater opportunity to thrive and grow to their fullest potential. As many of our reduced landscape areas are forcing trees into tighter and tighter spaces, healthy trees are being placed into more constricted growing zones that give no allowance for the critical tree root growth and are in direct conflict with underground or overhead utilities. Relatively new technologies are literally opening up new avenues for tree roots where they didn't exist before. But the application of these technologies need to be more than encouraged if we are to expect our street landscapes to grow to the desires of the community. As we adapt to these higher density issues, we need to apply the methods to allow for the trees to adapt as well. If developments are going to continue to force required landscaping into the streets and sidewalks with their inherent city maintenance costs, it is fair to consider 'less traditional' practices of construction that will benefit the community and the trees in the long term.
- Suggested Reading: Tree Space Design (see attachments); Article XIII Dallas Form Districts; Structural Soils; Silva Cells; Rootwell
10.105 Protection of Planting Areas
Required areas for plant materials must be protected from vehicular traffic through the use of concrete curbs, wheel stops, or other permanent barriers. (Ord. Nos. 22053; 25155)
10.106 Irrigation Requirements
All plant materials used as screening under this article must be irrigated by an automatic irrigation system installed to comply with industry standards. Other plant materials used to comply with this article must be located within 100 feet of a verifiable water supply. Proposed watering methods (irrigation or otherwise) must be:
(a) indicated on the landscape plan, if any; and
(b) adequate to maintain the plant materials in a healthy, growing condition at all times. (Ord. Nos. 22053; 25155)
- Revised to require a verifiable water supply for watering existing trees during the construction process, and to authorize the building official to approve alternative irrigation plans for properties seeking compliance with green building standards.
- Discussion: If the standard code is applied, the city arborist recommends a definition for 'verifiable water supply' to mean 'an established (to place or settle in a secure position) water source accessible to each plant and fully sustained (kept in existence and maintained) on the property.' It has also been suggested by UFAC for the building official to be authorized to approve an alternative irrigation plan that is 1) designed to comply with the general maintenance requirements of 10.108 and that is 2) designed by qualified professionals per city regulation when a lot or tract seeks qualifications for credit under green building, or equivalent, standards.
- Suggested Reading: Irrigation Ordinance (see attachment below)
City of Dallas Irrigation Requirements
IRRIGATION - WaterWise Landscaping (TNLA)
Landscape Irrigator, Technician and Inspector (TCEQ)
Ordinance Approach To Water Conservation (TX Urban Landscape Guide)
10.107 Planters Allowed
Planters may be used to satisfy the requirements of this article provided that the soil requirements in Section 51A-10.104 are met. (Ord. 22053)
- Discussion: Planter volume must be the same as the minimum required for the tree type. Volume is measured on the inside of the container.
10.108 General Maintenance
(a) Required plant materials must be maintained in a healthy, growing condition at all times. The property owner is responsible for regular weeding, mowing of grass, irrigating, fertilizing, pruning, and other maintenance of all plantings as needed. Any plant that dies must be replaced with another living plant that complies with this article and the approved landscape plan, if any, within 90 days after notification by the city.
(b) Any damage to utility lines resulting from the negligence of the property owner or his agents or employees in the installation and maintenance of required plant materials in a utility easement is the responsibility of the property owner. If a public utility disturbs a landscaped area in a utility easement, it shall make every reasonable effort to preserve the plant materials and return them to their prior locations after the utility work. If, nonetheless, some plant materials die, it is the obligation of the property owner to replace the plant materials. (Ord. 22053)
- Discussion: It has been suggested by the city arborist that in order to address specific landscape compliance for LEED or other programs, a provision should state 'all facilities that are landscaped in compliance with LEED or other crediting programs must be maintained in accordance with the conditions of that program. Any facility that is determined by the city to be in non-compliance, or is not credited due to lack of proper maintenance (per this section), must bring the site back into compliance, or revise the standards of accreditation, within 90 days after notification by the city. A record of maintenance program must be provided to the building official.' This standard may be considered if it is deemed by council that enforcement of specific green building standards is warranted. In addition, for the purpose of site stabilization and containing erosion, the following condition has been suggested from the Stormwater Management office. It states 'a uniform perennial vegetative cover of at least 70% of the native background vegetative cover of the area shall be planted or seeded on all unpaved areas and areas not otherwise covered by permanent structures, unless an alternative plant material or cover has been approved, or an alternative application time period has been approved.' The conditions would be imposed prior to final landscape inspection and administered for compliance within 30 days after notification by the city. Synthetic turf would need to be determined to be an acceptable ground cover material or not. Stormwater regulations would apply to all introduced synthetic surfaces.
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