§ 154-20.03  Landscape Design Standards.
   (A)   Landscape design.
      (1)   Recommended Plants List. Plant materials shall be selected from the City of Yuma Recommended Plants List, as found in the latest edition of the city landscaping guidelines.
      (2)   Xeriscape. Xeriscape landscaping incorporates water-conserving designs that take into account soil and drainage factors, microclimates, grouping of plants with similar water requirements, efficient irrigation systems, native vegetation, paving permeability, and low-water-using and drought tolerant vegetation. Xeriscape landscaping is not limited to cacti, boulders, and gravel; nor shall “xeri” be interpreted to mean “zero”.
      (3)   Irrigation required. All landscape areas shall include a permanent, water efficient, underground irrigation system controlled by automatic valves.
      (4)   Hydrozones. A key to the establishment of xeriscape landscaping that conserves water is to arrange plants in appropriate locations and not to interplant them with others that have different (i.e. higher or lower) water requirements. This grouping of plants into hydrozones is based on their water needs, and allows them to be irrigated and maintained efficiently. Plants with similar water use should be grouped together in distinct hydrozones.
      (5)   Existing trees. Existing trees preserved on a development site where the area under the canopy remains undisturbed and protected may be credited toward landscape tree requirements.
      (6)   Visibility triangles. Only landscape materials less than 30 inches in height are permitted in any visibility triangle, as defined in the latest edition of A Policy on Geometric Design of Highways and Streets published by the American Association of State Highway and Transportation Officials (AASHTO).
      (7)   Arizona Department of Transportation (ADOT) right-of-way. Parkways within the Arizona Department of Transportation (ADOT) rights-of-way shall be landscaped with trees, shrubs, and groundcover in conformance with the ADOT regulations.
      (8)   Public utilities and fire facilities.
         (a)   A minimum of three-foot wide clear space shall be maintained around the circumference of fire hydrants and Fire Department Connections (FDC). Groundcover materials used within this three-foot wide area shall be approved by the City of Yuma Fire Marshal.
         (b)   Trees shall not be planted directly under or over utility lines nor shall they be planted within utility easements. Trees which have a mature height of 25 feet or greater shall not be planted within 15 feet of overhead utility lines.
         (c)   A ten-foot clearance shall be maintained in front of the facilities and appurtenances of any public utility and a three-foot clear space shall be maintained around the circumference of any such facility or appurtenance. Groundcover materials used within this area shall be approved by the appropriate public utility.
      (9)   Protection of planted areas. Turf areas shall be separated from other planting areas by a minimum four-inch by four-inch concrete mow strip. Planted areas shall be separated from any adjacent paved or unpaved vehicular parking or drive area by concrete curbing measuring at least six inches by six inches above grade. Any plant material with a mature height of 18 inches or greater shall be set back at least two feet from any adjacent parking, aisle, or driveway.
      (10)   Provision of soil treatment. All non-vegetative planting areas shall be prepared with treatments to eliminate native seed germination. Typical methods for treatment include chemical pre-emergent sprays, soil fabric, mechanical removal, or a one and one-half inch ABC base beneath the non-vegetative groundcover.
   (B)   Plant and hardscape material.
      (1)   Trees.
         (a)   Purpose. Trees provide environmental, aesthetic, safety, and economic benefits. Environmentally, trees provide shade which reduces urban heat island effect, absorb carbon dioxide, and reduce stormwater runoff. Aesthetically, trees provide visual enclosure to streets, accentuate spaces, and add a human scale. Street trees serve to calm traffic speeds and absorb noise. Trees are known to increase property values and encourage pedestrian activity in retail environments. Trees are an important component of achieving effective Complete Streets, a policy adopted by the City in the Transportation Element of the City of Yuma General Plan.
         (b)   Types. Trees are classified in the City of Yuma Recommended Plants List as follows:
            1.   Street trees. Street trees are those that grow to an average mature height of 30 feet or more, generally have a high branching pattern, and upright or rounded crown form. Street trees are planted near the sidewalk or street to provide shade to pedestrians and visual enclosure to the street. The best species for street trees are low maintenance and produce low litter. Street trees shall be pruned and maintained to allow for minimum of 12 feet of clearance over any roadway and seven feet of clearance over any sidewalk.
            2.   Shade trees. Shade trees are those that grow to an average mature height of 30 feet or more, an average spread of 30 feet or more, and typically have a dense canopy that provides shade. The branching structure can be more spreading, vase-shaped, or layered than street trees.
            3.   Accent trees. Accent trees are small, ornamental trees that typically grow to a mature height of 15 to 20 feet. Accent trees can be used near overhead utility lines where tall trees are prohibited. Accent trees also include palm trees and saguaro cacti, although palms may not be used near overhead utility lines. Accent trees can be used to substitute required street or shade trees at a rate of two accent trees for each required street or shade tree.
   FIGURE 1: Types of Trees
         (c)   Distribution and placement.
            1.    Street trees shall be placed at a maximum interval of 35 feet along all street rights-of-way.
            2.   Street trees shall be placed four to eight feet from the sidewalk or curb, and when space allows they shall be located in the tree belt between the street and the sidewalk.
   FIGURE 2: Street Tree Placement
            3.   No tree shall be planted closer than four feet from the sidewalk or curb or closer than eight feet from any vertical structure or subdivision wall to avoid upheaval damage caused by the roots, unless other structural soil or stabilization methods are implemented.
   FIGURE 3: Tree Placement to Avoid Upheaval
            4.   Trees may be clustered; however no tree shall be located within 20 feet of another tree.
         (d)    Size. Required trees shall be planted at a minimum size (height, width, and caliper) as specified in the latest edition of the Arizona Nursery Association’s “Container Grown Tree Guide”, a copy of which will be maintained on file by the Department of Community Development. For every project, the container size for 50% of the required trees shall be a minimum of 24 inch box and 50% shall be 15 gallon container.
         (e)   Minimum required uncompacted soil per tree. Each tree well shall have a minimum of 150 cubic feet of uncompacted soil. Provisions for the required uncompacted soil shall be reflected in the landscape plan and details. If the minimum volume of uncompacted soil cannot be provided, structural soils or structural planting aides may be used to prevent compaction under paved surfaces.
         (f)   Staking. All trees shall be staked with two lodgepole stakes seven feet in height above grade with wire ties protected with rubber fittings. Staking details shall be shown on the plans submitted for approval.
         (g)   Mix of species. As it is desirable to have a mix of species and genera represented in the urban forest in order to protect against the loss of trees due to disease, insects, or environmental conditions, the following guidelines shall be used:
            1.   Plantings of five or fewer trees may all be of the same genus;
            2.   Plantings of six to ten trees must use at least two different genera, with roughly equal numbers of each;
            3.   Plantings of more than ten trees shall use no more than 30% of trees in any one genus.
      (2)   Shrubs.
         (a)   Purpose. Shrubs serve to provide visual screening between uses, create a colorful focal point, stabilize soils, cut glare, and prevent evaporative water loss.
         (b)   Distribution and placement. Shrubs shall not be placed in a planting area less than three feet wide, in either the width or length dimension. Shrubs can be clustered at driveway entrances, building entrances, property corners, and around signage to create distinct focal points. Encroachment into the visibility triangles shall not be permitted.
         (c)   Size. Required shrubs shall have a minimum mature growth height of 18 inches. For every project, the container size for a minimum of 50% of the required shrubs shall be five gallon, and in no case shall any shrub container size be less than one gallon.
      (3)   Groundcover. Required groundcover may be of two types, vegetative or inert.
         (a)   Purpose. Groundcover serves to reduce dust, stabilize soils, cut glare, and prevent evaporative water loss.
         (b)   Vegetative groundcover consists of living plant materials generally characterized by primary horizontal growth, as well as secondary vertical growth generally not exceeding 18 inches in height and includes grass/turf. Vegetative groundcover is not required, but groundcover plants of a one-gallon container size may be used to substitute required shrubs at a rate of three groundcover plants per one required shrub. Refer to the Recommended Plants List for groundcover plant species approved for use in City of Yuma rights-of-way.
         (c)   Inert groundcover consists of landscape rock such as gravel, decomposed granite, or crushed rock, with a minimum size of one-quarter inch screened. Unscreened road base material is not an acceptable material. Other materials, such as artificial turf, are also approved.
            1.   All non-turf areas shall be top dressed with inert groundcover such as landscape rock or approved alternative and supplemented and replaced as needed.
            2.   In all landscape areas, landscape rock of a color other than Yuma Grey is preferred. Except in retention basins, if the landscape rock is Yuma Grey, the following applies:
               i.   A minimum of 20% of the total required landscape area must be rip rap of a color other than Yuma Grey. The size of the rip rap is to be a minimum of three inches and a maximum of eight inches.
               ii.   One boulder is required for every 500 square feet of total required landscape area, with the boulders of a color other than Yuma Grey. Minimum size of the boulders shall be 18 inches.
            3.   Colored gravel is required in all landscape areas within special zoning district overlays, including: the Auto Center Overlay, the Aesthetic Overlay, and the Historic District Overlay.
      (4)   Prohibited plants.
         (a)   The use of the following plant types is prohibited due to their pollen and seeds which aggravate allergies and other health problems:
            1.   Common Bermuda grass (Cynodon dactylon);
            2.   Mulberry, female (Morus spp.); and
            3.   Olive (Olea europaea) except the male or fruitless varieties.
         (b)   The use of the following plant types is prohibited within the City rights-of-way areas due to their tendency to create visibility problems as well as because of their invasive root structures.
            1.   Palms;
            2.   Ficus;
            3.   Elm; and
            4.   Eucalyptus.
('80 Code, App. A, § 181)  (Ord. 583, passed 9-16-1952; Ord. 2584, passed 9-16-1992; Ord. O96-77, passed 8-7-1996; Ord. O2010-32, passed 7-7-2010; Ord.O2014-06, passed 2-19-2014; Ord. O2017-024, passed 8-2-2017)  Penalty, see § 154-999