COT_Tree_Care_Standards_2023.pdf

City of Tucson

Standards and Best Practices for Trees

(updated 9/19/2023)

Chapter 1 Valuing Our Trees

Chapter 1 Introduction

Chapter 1 Guiding Standards

Chapter 2 Tree Selection

Chapter 2 Tree Selection Standards

Chapter 2 Best Management Practices

2.1 Nursery Stock

2.2 Root Structure

2.3 Inspect the Tree

2.4 Field Guide

Chapter 3 Site Selection

Chapter 3 Site Selection Standards

Chapter 3 Best Management Practices

3.1 Utilities

3.2 Spacing and Clearance

3.3 Site Selection

3.4 Functional Goals

3.5 Urban Forest Biodiversity

3.6 Volunteer Trees

3.7 Field Guide:

Chapter 4 Planting

Chapter 4 Planting Standards

Chapter 4 Best Management Practices

4.1 Planting

4.2 Mulch

4.3 Fertilizer and Herbicides

4.4 Staking

4.5 Irrigation

Chapter 5 Care and Maintenance

Chapter 5 Best Management Practices

5.1 Watering

5.2 Maintenance

5.3 Inspect the Tree

5.4 Pruning

5.5 Proper Pruning Techniques

5.5 Pruning Methods

5.6 Unacceptable Pruning Practices

5.7 Timing

5.8 Removal and Replacement

5.9 Field Guide:

Chapter 6 Safety

Chapter 6 Safety Standards

Chapter 6 Best Management Practices

6.1 General safety

6.2 Emergency procedures

6.4 Electrical Safety

6.5 Vehicle and Equipment Safety

6.6 Tool Safety

6.7 Climbing Safety

Definitions

Chapter 1 Valuing Our Trees

What is the Urban Forest and Why Do We Care For It?

Chapter 1 Introduction

What is the Urban Forest and Why Do We Care for It?

“What happens when you plant a tree? What happens when you wield a shovel in one hand (a human artifact) and a tree (a provisional mystery) in the other? What happens when you dig a hole (a Kali-like destruction) and plant a tree within it (an act of creativity)? What happens when you learn about your local ecology not just as an observer, but also as a participant? What happens when you embrace the wildness of a tree-being and integrate it into the semi-wild streets and streams of your local community? What happens when you crack open your isolated sense of self and plant within your heart this symbol of our ever-branching inter-being? What happens when you consider your actions in terms of your ecological and cultural legacy?”

― Robin Wall Kimmerer, Braiding Sweetgrass

Life in the Sonoran Desert is a daily gift. The Sonoran Desert is the most biologically diverse desert in

North American; home to over 550 animal species and over 2,000 plant species.

We honor the tribal nations who have served as caretakers of this land from time immemorial and respectfully acknowledge the ancestral homelands of the Tohono O’odham Nation and the multi-millennial presence of the Pascua Yaqui tribe within Pima County.

We honor trees as our neighbors and relatives, as critical living infrastructure, and as the stewards of our shared space. Our urban forest is the land we share, the air we all breathe, the shade we seek, the water we drink, and the joy we spread. The trees we water and care for today are the future we are building for future generations. The trees we plant today are investments against our changing climate to cool and keep livable the Tucson of the next 10, 50, 1000 years.

In Tucson we all know the feeling of stepping from the hot pavement to the incredible shade of a velvet mesquite - we have all breathed that particular sigh of relief. That individual mesquite started as a seed, carefully tended by the correct mix of soil, water and sunlight to grow despite the heat of the urban environment, constraints of other grey infrastructure around it, the threat of weed whackers and everything else that can work against green space in our urban spaces. As that tree grew, a person was kind and skilled enough to care for it, offer water when drought plagued the city, carefully prune it to ensure the tree’s health and to maximize the shade offered by the growing leaves and limbs. People are stewards of an urban space, the urban ecosystem, and care and maintenance is required to keep our urban trees and spaces healthy and gifting us with the most possible benefits. What we put into our urban greenspace we will get back many times over because our trees and ecosystems have made this land livable for generations before us.

Pima County Land Acknowledgement –

“On behalf of Pima County residents, we honor the tribal nations who have served as caretakers of this land from time immemorial and respectfully acknowledge the ancestral homelands of the Tohono

O’odham Nation and the multi-millennial presence of the Pascua Yaqui tribe within Pima County.

Consistent with Pima County’s commitment to diversity and inclusion, we strive toward building equal-partner relationships with Arizona’s tribal nations.

Chapter 1 Guiding Standards

One of the most structurally visible public landscape feature is trees. Trees provide functional, social, and aesthetic benefits to the City. Public trees are one of the only public assets that appreciate with time.

This Standards and Best Practices of Trees establishes best management practices to accompany the implementation of:

• Establishing a point(s) of contact for tree maintenance: 1) the Urban Forestry Manager 2) the

Director of Parks & Recreation; with assistance from the Director of Transportation or designated urban forestry/landscape manager when related to trees in the City’s rights-of-way

• Pima Association of Government Standard Details and Specification for Public Improvements, 2015 edition, and subsequent updates

• Tucson Community Forest Action Plan 2023

• Current standards established by the American National Standards Institute (ANSI) Z133.1: Safety

Requirements for Pruning, Trimming, Repairing, Maintaining, and Removing Trees and for Cutting

Brush

• The International Society of Arboriculture (ISA), best management standards and maintenance practices

• Most nursery tree stock in Southern Arizona are sold in a containerized form. The following standards are specific for containerized stock. If using a different nursery stock, refer to the appropriate International Arboriculture (ISA) guidelines for planting instructions

• The Arizona Nursery Association Growers Committee Recommended Tree Specifications standards

• Guidance from Tucson Clean and Beautiful

• OSHA Safety Rules and Regulations (OSHA 29 CFR 1910) relating to safety standards when pruning near electrical and communication power lines

• City of Tucson Municipal Code Part II: Tucson Code: Chapter 25: Streets and Sidewalks Article II:

Duties and Prohibitions Sec. 25-53. Duty to trim:

o The owner, occupant, or agent in charge of any lot, piece, or parcel of land within the corporate limits of the city shall not allow any tree, shrub, or other form of vegetation of any kind upon such property or upon the right-of-way, street, or alley adjoining the same to extend over or under the sidewalk space or roadway in such street or alley in such a manner as to interfere with the reasonable use of such street, sidewalk, or alley for pedestrian or vehicular devices or luminaries. It shall be the duty of every such owner, occupant or agent in charge to keep such trees, shrubs, or any other vegetation trimmed in such manner that the same will not interfere with the reasonable use of such street or alley for pedestrian or vehicular traffic. (1053 Code, ch.24§16; Ord. No.

6195, § 3, 3-11-85; Ord. No 8327, § 2,7-5-94)

Chapter 2 Tree Selection

Chapter 2 Tree Selection Standards

The City shall make every effort to ensure that it plants only vigorous, healthy trees and make every effort to choose quality stock in the nursery. The standards for selecting acceptable nursery stock shall be as follows:

• All trees should be selected from the Arizona Department of Water Resource’s Low Water

Use/Drought Tolerant Plant list

• All trees shall be well potted with no evidence of being root bound, or having girdling or kinking roots

• All trees should be true to type and species shown on planting plan

• All trees shall be selected for health with a straight trunk with good taper and symmetrical form

• Multi-trunk trees shall exhibit a healthy, multi-trunk form with structurally sound unions

• All trees shall exhibit even branch distribution and no visible damage to the trunk

• No trees will be accepted that are severely topped, headed back, pollarded, or lion-tailed

• All trees shall comply with Federal and State laws requiring inspection for plant diseases and infestations https://new.azwater.gov/conservation/landscaping https://new.azwater.gov/conservation/landscaping

Chapter 2 Best Management Practices

Figure 1. How to examine a nursery tree

2.1 Nursery Stock

Trees in containers shall have been growing in the container for an appropriate period of time for uniform root growth and stability. All trees will be inspected by a City authorized professional upon delivery to the site and prior to storage or planting (Figure 1). The City shall reserve the right to refuse any nursery stock that does not meet the standards and may require any person such as an external contractor, landscaper, or installer, who has planted sub-standard trees on City property or within City right-of-way to have those trees removed and replaced at that person's expense.

Proper nursery potting practices are important for ensuring a containerized tree’s health. Improper practices can lead to issues such as; being root bound, girdling routes, needing root pruning. Double check for roots emerging from the drainage holes in the bottom and if present look for another specimen. Having too few roots can be equally troublesome. If not properly rooted in the pot, it will be very difficult to plant successfully, and the root ball may not remain intact once removed from pot. This may lead to transplant shock or death of the tree. Some of these issues can be fixed at planting, but it is better to avoid buying trees with root problems. To check the root ball condition and root health, grasp the trunk about halfway up from the soil level and shake gently - the trunk should bend/move, but where the trunk enters the potting soil should remain stationary.

2.2 Root Structure

The root structure of the tree shall have no evidence of girdling, kinking roots, or be root bound. Circling or girdling roots will cause long-term health issues and eventual failure. A buried root flare will also cause long-term issues.

To check tree health in the container:

Step 1 Dig fingers into soil adjacent to trunk until you encounter primary structural root branching off of the main stem

Step 2 The structural root should be growing straight out from the main stem, not turning or circling or diving down

Step 3 The first structural root should also be right at the soil surface

Step 4 If it does not pass this inspection, do not purchase

Step 5 Repeat this inspection on the next tree in the nursery until you find a good specimen

2.3 Inspect the Tree

All trees shall meet the minimum size standards of the “Arizona Nursery Association Growers

Committee Recommended Tree Specifications.” Inspect the entire tree for health and form. Look for trees with one dominant trunk, branches that do not cross, full and uniform canopies, and free from damage, disease, pests, and structural problems. Trunks remain vertical without support and free of damage. Please note, with most native desert trees a multiple trunk is a healthier and stronger form and should be encouraged in the right planting location.

Consider selecting trees for health over beauty:

• Trees are often pruned up in the nursery to appear taller and bigger, which robs the young tree of vital energy and slows down root and trunk development making it much harder for the tree to thrive once planted in the landscape

• If the lowest lateral branches on a tree are removed too early, the tree will be unable to develop a proper root flare, which is important for long term strength and structural stability

• Excessive pruning of lower branches on a young tree expose the tender bark to the harsh desert sun, increasing the chances of sunburn and potential death

• Generally, planting longer-lived species reduces maintenance costs and future replacement costs

2.4 Field Guide

Trees in larger pots are not always better. The longer a tree has been in a pot, the more structural issues its roots may have. Root structure issues are difficult to impossible to remediate. Younger and smaller potted trees (i.e.,5-gallon) often perform better in the landscape than trees planted from larger nursery pot or box sizes (i.e., 24" box). 5-gallon trees typically have better/healthier root structures than 15-gallon trees or 24” box trees and will even outgrow an identical species planted at the same time. If a potted tree larger than 15-gallons needs to be planted, a City authorized professional or ISA Arborist with planting and root health expertise should be employed to install those trees.

If the roots of the nursery tree are healthy upon inspection it will be more likely to grow and thrive after planting. If the roots are in poor condition, the tree is more likely to suffer and die within 5-10 years of planting. Select your nursery stock based on root health, not size or appearance.

If there is succession planting built into the landscape plan, it is acceptable to plant a mix of faster-growing trees to produce more shade sooner. Tougher species which will fill in and provide long-term shade and beauty as the short-lived trees reach their lifespan and start to die off.

References: ISA Best Management Practices - Tree Planting, Second Edition (2014), American National

Standard for Tree Care Operations – Tree, Shrub, and Other Woody Plant Management—Standard

Practices (Planting and Transplanting), Arizona Department of Water Resource’s Low Water

Use/Drought Tolerant Plant list, City of Tucson Landscape Maintenance Manual, Arizona Nursery

Association Growers Committee Recommended Tree Specifications

Chapter 3 Site Selection

Chapter 3 Site Selection Standards

The City shall make every effort to follow the best practice of planting the right tree in the right place.

The standards for site selection are as follows:

• All trees should have adequate growing space and consider maximum tree height and width

• All tree planting sites should have the required available soil volume and soil surface area

• All trees shall follow City setbacks for utilities

• All trees shall follow city code landscape standards 7.6 and 7.7

• All trees shall follow the clearance requirement of 15’ between a road to the bottom of tree canopy and 7’ between a sidewalk or path to the bottom of a tree canopy

• Trees shall be planted in areas to ensure the visibility of roadway signs and to maintain clearance from bike lanes

• All sites should consider environmental conditions

• When planting multiple trees, the design should promote biodiversity and avoid monoculture sites, or the planting of one singular tree species

Chapter 3 Best Management Practices

3.1 Utilities

Always look above, below, and around when identifying a location to plant your tree. Before you plant, schedule Blue Stake (Arizona 811) to locate underground utilities before digging. Space considerations are as follows:

Required Plant Setbacks from Underground Utilities

Utility Large Tree over

20’

Plants under 20’ tall

Plants under 3’

Southwest Gas 8’ 5’ 3’

Pima C. Sewer 16’ 10’ 5’

Electric UG 3’ 3’ 3’

Tucson Water 10’ 5’ 3’

Cable / Fiber Opt 8’ 5’ 3’

No Planting in El Paso Gas Easements

3.2 Spacing and Clearance

Plan appropriate spacing for different tree species. Ensure space for a tree’s mature canopy size. If planting trees adjacent to another tree, tree canopy may overlap by approximately 15%. Some situations may allow for closer plantings and thicker canopy such as a small-scale urban forest. Allow minimal overlap at maturity for easier maintenance.

Any native or desert-adapted tree planted in the urban environment should be installed 3’ + Mature

Trunk Radius from any adjacent hardscape to allow for maximum trunk development and reduce damage to surrounding surfaces. A tree planted 8’ from a building will provide adequate space for canopy growth. Assess the available space in a ROW before planting a tree and ensure adequate soil volume and the size of the mature tree.

To help guide site selection and maintenance, follow sight visibility triangle (SVT) clearance (Figure 2). At crosswalks and intersections, an unobstructed and continuous view of both the intersection and intersecting roadways helps pedestrians, cyclists, and drivers avoid conflict. Trees should be pruned to 7’ between ground and to the bottom of a tree canopy for SVT clearance. Shrubs should not exceed 30” in height.

Figure 2. Sight Visibility Triangle guidance.

3.3 Site Selection

When planting or replacing trees, consider the tree’s mature size (Figure 3) and growth form as it relates to the planting location. Selecting an appropriate tree can help to minimize pruning needs, clearance concerns, and damage to adjacent infrastructure. Include the functional goals of the tree when selecting its site. Ensure an adequate and reliable water source.

Figure 3. Mature tree basin.

The soil must be suitable for root growth. Ensure adequate soil volume, 300 cubic feet of soil volume should be provided to urban trees. Large, mature trees require up to 615 cubic feet of soil volume. For new planting areas, remove all pavement, gravel sub-base and construction debris; remove compacted soil and add new topsoil.

Follow all spacing and clearance standards and choose the right tree for the right place.

Figure 4. Tree placement for year-round services.

Consider the potential impact from sun and heat exposure to the tree (Figure 4 and Figure 5). Consider reflected heat off pavement. Hardscape surfaces like masonry walls, concrete sidewalks, or asphalt paving can expose newly planted trees to increased reflected heat.

Plant deciduous trees on the south and west sides of buildings. Following this site selection guideline, the tree will provide shade during the summer months and let warmth in during the winter months.

Figure 5. Tree placement for energy efficiency based on seasonal sun patterns.

There are many stressors in urban settings that can reduce the lifespan of trees. In particular, planting trees in hot asphalt parking lots is a difficult environment for trees to thrive. In addition to the City of

Tucson standards and best practices for trees, consider the following recommendations. Allow trees to grow and establish trunk taper. Prune for clearance once the tree develops. Prune properly and minimally to meet the desired clearance goal and avoid over pruning and improper pruning practices like lion tailing, topping, or hedging. Choose trees free of spines and excessive litter. Plant trees to tolerate reflected heat. Avoid planting trees in undersized islands with inadequate soil volume. Consider planting trees in large, linear islands or sites that promote stormwater harvesting.

3.4 Functional Goals

Consider desired goals of the site and how the tree supports the goals. Trees provide the following benefits in urban settings:

• carbon sequestering

• urban heat island mitigation

• beautify the urban environment

• mental health benefits

• wildlife habitat

• food production

• make oxygen

• shading parking

• shading bus stops

• shading roads and pedestrian routes

• collaborating with other urban infrastructure

• reduce crime,

• improve quality of life

3.5 Urban Forest Biodiversity

It is important to consider planting a variety of species at planting sites to avoid a monoculture site.

Monoculture refers to a planting site that has many of one species or a low diversity of species.

Monocultures are more susceptible to disease and other failures that reduce the life span of the trees.

Plant multiple species to increase biodiversity and strengthen the urban forest’s resilience.

3.6 Volunteer Trees

Volunteer trees are seedlings that sprout from wild seeds without human interference. A volunteer tree typically sprouts near a source of water like irrigation emitters or an area where water collects after rain. Many volunteer trees need to be removed because the species is undesirable, it is too close to pavement, or too close to existing trees. If the volunteer tree is in a suitable site, is a desirable native species, and can be supported with little or no irrigation, the tree should remain.

3.7 Field Guide:

On the North and East sides of tall buildings, plant trees that prefer cooler sites such as a canyon hackberry or desert willow. These riparian species prefer cooler sites that resemble a riverbed. Plant trees that tolerate hot and sunny sites with reflected heat such as ironwoods.

For street plantings, use trees that tolerate pruning well and generally hold a more upright shape that can be trained taller over time. The Tucson Community Forest Action plan recommends the following trees for street plantings: catclaw acacia, texas ebony, screwbean mesquite, palo blanco, foothill and blue palo verdes, and willow acacia. In addition, ironwoods are recommended because of their slow growth but can spread out after the first 20 ft. Foothill palo verdes and blue palo verdes grow slow, require low maintenance, and require ample space for root system, but can be considered for street plantings.

Avoid planting large trees under utility lines as they will likely grow into the lines or require significant and frequent pruning to preserve clearance. Even a desert willow can grow over 20’ tall. Consider using large shrubs instead of trees when overhead utilities are present. Some recommendations of large shrub species are as follows: white thorn acacia tree, kidneywood tree, creosote bush, jojoba bush, desert hackberry bush, wolfberry bush, and greythorn bush. Note the need to prune the bushes for SVT clearance and to best fit under utility lines.

Velvet mesquites or any South American mesquite and desert museum palo verde should be reserved for park environments away from vehicles and structures. If planting adjacent to parking spaces, site center trunks on dividing lines to prevent trunk damage by vehicle bumpers overhanging the edge of pavement.

Consider soil type when planting. Sweet acacia and foothills palo verde do not prefer heavy clay soils and grow in poor, rocky, caliche filled, fast draining soils. Canyon hackberry and screwbean mesquite prefer heavier clay soils that hold moisture. Ironwoods can thrive in almost any soil type in Tucson.

References: ISA Best Management Practices - Tree Planting, Second Edition (2014), American National

Standard for Tree Care Operations – Tree, Shrub, and Other Woody Plant Management—Standard

Practices (Planting and Transplanting), Arizona Department of Water Resource’s Low Water

Use/Drought Tolerant Plant list, City of Tucson Landscape Maintenance Manual, Arizona Nursery

Association Growers Committee Recommended Tree Specifications, Storm 2 Shade GSI Field Guide, Tucson Community Forest Action Plan, and Tucson Electric Power Planting Utility planting Guide

Chapter 4 Planting

Chapter 4 Planting Standards

The City shall make every effort to ensure that trees are planted properly. The standards for tree plantings are as follows:

• All trees on public property shall be planted by a City authorized professional

• All tree containers, burlap, wires, twine, or other materials shall be removed from root ball and canopy unless specified by a City authorized professional

• All trees shall be planted immediately after container removal

• The planting hole shall be dug no deeper than the root ball

• All planting holes shall be at least 2-3 times wider than the root ball, and up to 5 times wider when space permits

• All tree planting soil shall be approved by a City authorized professional

• All nursery stakes shall be removed unless specified by a City authorized professional

• All trees planted on public property shall have a planned source of irrigation, no planting shall be done until acceptance of the irrigation plan

• All trees at risk of mechanical stress such as damage from a string trimmer, lawn mower, or rodents should receive protection such as arbor guards, fences, herbivory, or mulch circles

Chapter 4 Best Management Practices

4.1 Planting

The schedule of planting shall be at the discretion of the City authorized professional. Planting holes shall be located and prepared by the City authorized professional.

Before trees are planted, check the planting hole for proper drainage. Most trees will suffer if planted in an area that retains too much water as soils can be anaerobic or lacking oxygen. To check, dig the planting hole and fill it with water. Check back in a few hours to see if the water has drained. If it has, the planting hole has appropriate drainage. If the water takes more than 24 hours to drain, consider adding a drainage chimney. A drainage chimney is a smaller hole punched through the bottom of the basin. To prepare the site for planting, soak the site 24 hours before planting to aid in digging.

Dig the planting hole no deeper than the root ball so the upper lateral roots are flush with the surface.

One of the most common mistakes is planting too deep. If planted too deep, the tree cannot exchange gas and nutrients at the base of the trunk and could cause the tree to fail. Dig the planting hole according to a minimum of 2-3 times wider than the root ball. If space permits, the planting hole can expand up to 5 feet, such as an open area. Consider the size of the root ball and tree when digging the planting hole.

Position the top of the root ball and the level of the backfill to the surrounding grade or planting plan.

Any plant that settles more than 1½ inches below the specified grade shall be reset or replaced.

Figure 6. Root treatment.

Gently remove the tree from its planting container. If root-bound, loosen the roots gently with your hands, or prune with a knife by slicing along one side of the root ball to allow the roots to begin growing outwards (Figure 6). All containerized trees are likely to have root issues without root pruning. Root pruning is the process of cutting back roots that may girdle. Targeted root pruning at planting can reduce long-term root complications but should be performed by a City authorized professional. After inspecting the roots and repairing them as necessary, place the tree into the planting hole (Figure 7).

Figure 7. A tree basin.

Backfill the hole with existing soil or prepared soil. If the space permits and recommended by the authorized planter, use leftover soil to form a temporary berm around the planting hole to serve as a watering well. The tree shall be thoroughly irrigated until the backfill soil around and below the root ball of each plant is saturated. Trees shall be watered the same day as planted. Do not add organic amendments such as compost to the backfill or put a sandy soil on top of a clay soil or vice versa. All tree planting soil shall be approved by a City authorized professional.

Figure 8. How to plant a tree.

If the any unforeseen or unsuitable planting conditions arise, it shall be communicated to the City authorized professional immediately.

4.2 Mulch

Spread a layer of organic mulch at a depth of 1” in the tree basin. The mulch spread should extend outward about 3 - 5 feet, or to the drip line of the tree for larger trees. The mulch should not touch the trunk or be piled up in a mound around the trunk. The trunk flare must always be exposed. Mulch moderates soil temperature, reduces weeds and erosion, preserves soil moisture, adds nutrients back to the soil, and supports microbial activity.

For planting sites that require riprap, turf, or rock around the tree, refer to the City authorized professional.

4.3 Fertilizer and Herbicides

Fertilizer or special amendments to the soil are not recommended at planting. Herbicides and pesticides may be applied by AZ State Certified Applicators with formal approval by the City.

4.4 Staking

Trees do not need to be routinely staked. In fact, staking may have detrimental effects on tree development. Stake if the tree cannot stand without support, is threatened by wind or other inclement weather, needs protection from damage caused by people or machinery, or advised by an ISA arborist

(Figure 9). Additionally, staking may be needed in sandy soils or for trees with small root balls. Stakes should be straight construction grade treated douglas fir, lodge pole pine or other species approved by

City planter. Stakes should be 8 feet in length with a diameter of 2 inches or greater. For large trees, use tie wire and webbing, tie wire and hose, or tie wire and tubing. Tubing includes ¾" black poly. For small trees, use horticultural tape to secure tree to stakes. Trees should be tied firmly and securely and with enough slack to allow the trunk to move. This movement is critical for the tree to develop trunk taper and strength. Stakes shall be positioned to clear the root system as to not damage the roots. Tree ties and support shall be routinely inspected and adjusted or removed as needed.

Trees that cannot stand on their own after one year of staking, should be considered for removal and replacement.

Step 1 Use only 2 stakes, preferably wood

Step 2 Place stakes a minimum of 12” away from the root ball and at least 6” deep into undisturbed soil

Step 3 Place ties at the highest point on the trunk at which it will not bend or at 2/3 of the total tree

Step 4 Cut stakes below the tree canopy to prevent wounds to the branches

Step 5 Inspect and loosen wires periodically

Step 6 Remove stakes as soon as possible, usually within the year

Figure 9. How to stake a tree.

Staking Pic

4.5 Irrigation

Irrigation is the application of supplemental water to the root system. Newly planted trees require frequent irrigation to keep the root ball from drying out. A plan for irrigation shall be considered and included during the tree planning process. Irrigation should be provided via an automatic irrigation system, hand watering, water harvesting, or a combination of all methods.

Build a berm or temporary watering well around your planting hole. Berm should be sized appropriately for the size of the planted tree and should be adjusted as the tree grows. Build the berm slightly beyond the drip line of the tree and continue to move it outwards as the tree grows. Make sure the highest point of the berm is on the downslope side of the tree. Consider how rainwater flows in the planting area and leave an opening on the upslope side to allow water running down from higher elevations to be caught by the berm.

Figure 10. Drip irrigation placement.

The City authorized professional shall be responsible for maintaining all existing irrigation lines (Figure

10). Irrigation system components damaged or destroyed during construction shall be evaluated by the

City authorized professional and if deemed necessary billed to the contractor responsible for the damage.

When planting trees as part of green stormwater infrastructure (i.e. in basins), it is best practice to provide an elevated planting shelf to ensure that the tree's root flare is above the flood level of the basin (Figure 11). This reduces the risk of the root flare getting buried with sediment or other organic materials which can lead to basal rot or other forms of tree failures.

Figure 11. Planting a tree next to a basin.

Consider how water flows at the tree planting site. Be mindful of existing slope (Figure 12).

Figure 12. Planting on a slope.

References: Pima Association of Government Standard Details and Specification for Public

Improvements, 2015 edition, and subsequent updates in 2019 and 2020, Tucson Clean and Beautiful

Chapter 5 Care and Maintenance

Chapter 5 Care and Maintenance Standards

The City shall make every effort to ensure that trees planted on City property are cared for and maintained to the following standards:

• Newly planted trees shall have an establishment period plan, or a tree care plan for the first two years

• All trees shall be watered deeply but infrequently according to the watering schedule

• All trees shall be pruned following proper pruning techniques with adherence to ANSI-A300 (latest edition) Pruning

• No tree shall receive treatments used to cover wounds or pruning cuts unless authorized by City planter

• It is against the law to remove or damage City of Tucson trees and plants

Most trees on residential streets belong to and are the responsibility of the adjacent property owner. If you are not sure, call the City’s Landscape Architect. (City Code Chapter 25)

Chapter 5 Best Management Practices

5.1 Watering

Newly planted desert adapted trees will require establishment watering for the first two years after planting. Once the tree is established, infrequent, supplemental watering is all that is required. In general, schedule a deep and long, 10-15 minute basin soak for 2-3x per week on all trees during the establishment period (Figure 13). Reduce water after establishment. Watering needs may vary based on different factors.

Figure 13. How to water a tree during the establishment period.

Consider the soil type, tree species, and available water. A soil test or percolation test identifies the soil texture, or mixture of clay, silt, and sand. Sandy and well-drained soils need more frequent irrigation.

High clay-content soils need less frequent irrigation.

If adhering to the Arizona Department of Water Resource’s Low Water Use/Drought Tolerant Plant list, all trees are low water use plants. But some survive on less water than others. For example, a palo verde tree requires less water than an evergreen elm.

Always follow City of Tucson and Tucson Water rules and restrictions on irrigation schedule. Typical water needs of established Tucson trees under normal weather and soil conditions are shown below.

https://www.tucsonaz.gov/water/landscape

City of Tucson Suggested Watering Schedule

Water Need of Species Summer watering interval

Fall, winter, spring watering interval

Example of Tree

Species

Very Low <90 degrees, 1-2x per week

>90 degrees, 1-2x per week

1x per month

Sweet Acacia, Willow

Acacia, Palo Blanco, Palo Brea, Blue Palo

Verde, Foothills Palo

Verde, Ironwood

Low <90 degrees, 1-2x per week

>90 degrees, 2-3x per

Canyon Hackberry, Desert Willow

Moderate <90 degrees, 2-3x per week

>90 degrees, 2-3x per

Chinese Pistache

High <70 degrees, check soil for dryness, water only when soil is dry

70 degrees - 80 degrees, 1x pe week

80 degrees - 90 degrees, 2x per week

>90 degrees, 3x per

2x per month

Live Oak, Aleppo Pine

Drip irrigation is an effective method for watering newly planted trees through establishment. Ensure that water is applied to the root zone and follow the deep and infrequent watering method. As the tree grows it is important to move irrigation emitters in line with the tree canopy's drip line. This encourages lateral root growth and enhances the trees stability. Irrigation schedules may need to be modified as irrigation needs are typically reduced over time. If hand watering a tree, a consistent watering schedule is critical for tree survival during establishment period.

5.2 Maintenance

During the establishment period, trees need minimal maintenance. Only consider pruning the tree during the first 2 years with proper training and credentials. Developmental pruning is important in the urban setting to help reach desired goals such as a single trunk tree along a street. If the tree is in a natural setting, such as a park, consider minimal developmental pruning. Organic material like leaf litter can be used for mulch within the tree's basin and should not be removed from site. Monitor the basin wall to prevent leaks. Regularly check the irrigation system for leaks and other malfunctions. Modify the watering schedule seasonally and based on the age of the tree.

Figure 14. Examples of common tree hazards.

5.3 Inspect the Tree

All trees should be properly maintained to improve tree vitality and reduce potential threats. Early detection and reporting of a sign or symptom could save the tree. Understand the proper process and procedure to evaluate a tree and the correct point of contact for reporting.

Complete a level 1 risk assessment based on ISA Tree Risk Assessment framework of the tree to determine whether mitigation or advanced care is needed. To examine, stand close to the tree and walk in a circle and inspect the roots, trunk, limbs, and leaves from each location. Once the circle is complete, move to the drip line and repeat. Note any signs or symptoms. Determine if there are large limbs that are likely to fail due to storm damage, rot, or other factors. It is better to remove a limb pro-actively than risk falling on a target such as a person or property. Follow proper pruning techniques as described in this section (Figure 14).

Evaluate the overall balance of the tree. Look for dead branches and crossed branches where the surfaces rub. Look for cavities or rotten wood. Examine the soil level and any hardscape damage at the base of the tree. Check the color of the leaves. Log the signs or symptoms and report to a City authorized professional.

The City of Tucson suggests an ISA certified arborist or City authorized professional performs the risk assessment. Remediation should be performed by or under the guidance of an ISA Certified Arborist with approval by the City or by a City authorized professional.

If biotic damage is observed, or stress by a living organism such as a pest or rodent, any necessary methods of control shall consist of either chemical or mechanical methods approved by a City authorized professional or under the guidance of an ISA Certified Arborist with approval by the City.

5.4 Pruning

Pruning is the removal of limbs and branches to maintain safety, improve tree health, or satisfy goals such as clearance or sight visibility. Proper pruning techniques can prevent injuries to trees that make them susceptible to decay or pest infestation, or lead to a loss of photosynthetic function.

Follow proper pruning technique standards (Figure 16). Reference ANSI A300 pruning standards or perform pruning under the direction of an ISA certified arborist.

Prune as minimally as possible to satisfy the goals of pruning. Step back and reassess goals frequently throughout the pruning process. Use the right tools and use clean tools. Pruning of large, mature trees or any pruning that requires use of ladders or climbing equipment is dangerous and difficult work and must be performed by personnel with the proper safety training and under the direction of an arborist certified by the International Society of Arboriculture.

Figure 16. Illustration of a good pruning cut and a bad pruning cut.

5.5 Proper Pruning Techniques

To prune small branches, up to ¾ inches in diameter make a sharp clean cut beyond the lateral bud or other branch. Use bypass pruners or loppers (Figure 17).

Figure 17. Tools for tree pruning.

To prune larger limbs, or branches over ¾ inches, use the 3 cut method. Cut 1- make an undercut through 1/3 of the branch. Cut 2- make the top cut slightly farther on the limb than the undercut to remove the branch. Cut 3- make final cut just outside the branch collar/branch bark ridge to remove the stub (Figure 18).

Figure 18. Large limb pruning.

A reduction cut trims back to the nearest lateral branch or to the main trunk (Figure 19). Ensure that the remaining lateral is at least 1/3 the diameter of the cut branch.

Figure 19. A stub cut and a reduction cut.

5.5 Pruning Methods

Pruning methods in the City include structural pruning, restoration pruning, rejuvenation pruning, and utility pruning. The objective of structural pruning is to promote good structure, reduce future maintenance, and improve canopy clearance requirements (Figure 20). Trees with good structure exhibit a strong central leader and have balanced and evenly spaced limbs. Structural pruning promotes the long-term health and shape of the tree by encouraging strong branch unions and natural shape through selective pruning on younger trees. Major structural defects to address and do not promote good structure include codominant branches and included bark. It is important to remedy major structural issues in young trees to avoid removal of large branches later on. As trees age, use the appropriate pruning method for desired goals.

Figure 20. Illustration of crossing branches and a dominant leader.

Structural pruning steps:

• Select a dominant leader that will be preserved

• Establish the lowest permanent branch

• Identify scaffold branches

• Locate codominant branches or included bark

• Choose the proper tool for the size limb and begin to prune

• Clean the canopy of any dead, broken, diseased, or dying branches (Figure 21)

• Remove branches that cross or rub against one another

• Figure 21. Image of a broken branch to prune.

The objective of restoration pruning is to repair a tree’s structure or appearance and minimize risk of disease or decay. Often used after storm damage such as a monsoon or high winds or after improper past pruning. Restoration pruning steps:

• Remove stub cuts

• Thin reaction growth

• If needed, allow a year to pass after a bad pruning cut and there is enough new growth to work with to make proper pruning cuts

• Reduce end weight on lion-tailed branches

The objective of rejuvenation pruning is to stimulate healing and new growth. Rejuvenation pruning steps:

• Remove limbs damaged by a storm, a frost, or by sunburn

• Remove dead or diseased growth

The objective of utility or clearance pruning is to comply with city codes and to meet sight visibility needs. On low-risk jobs, follow proper pruning techniques. Pruning anything within 10 feet of assumed energized power lines should be done only by a trained authorized professional during a scheduled power kill by utility. Power line clearance pruning has added risk and must be performed by personnel with the proper safety training and only under the direction of an arborist certified by the International

Society of Arboriculture.

Figure 22. A codominant trunk and a topped tree (Figure 22).

5.6 Unacceptable Pruning Practices

Do not prune by topping or ‘lion tailing.’ These are common mistakes and not permitted on City of

Tucson Trees. The City of Tucson shall reserve the right to refuse any services that do not meet the standards, and may require any person such as an external contractor, landscaper, or installer, who has pruned trees on City property or within City right-of-way to have those trees removed and replaced at that person's expense (Figure 23). If unsure how to prune a tree, please communicate with a City of

Tucson representative before services are performed.

Topping removes leaves and the ability for the tree to produce food. Once topped, a likely reaction will be rapid growth of multiple shoots. This practice is not permitted on City of Tucson trees.

Lion tailing exposes the trunk of the tree and may result in sunscald. Additionally, the tree will be structurally compromised by removing interior branches making it more of a hazard. This practice is not permitted on City of Tucson trees.

Figure 23. An illustration of a lion tailed tree.

5.7 Timing

Light pruning can be performed at any time throughout the year with little negative effect. For more significant pruning it is recommended to prune between November and March. Pruning large limbs in the summer can have negative consequences on the health of the tree due to the creation of a large wound and the exposure of the trunk to the sun. Additionally, large wounds are more susceptible to pests and decay.

Ideally, prune before the buds swell. Time of year:

• While dormant, November-March is best in Tucson

• Be mindful of bird breeding seasons, most birds breed between February and May

• Avoid pruning major limbs during the summer, especially if bark beetles might be present

5.8 Removal and Replacement

A tree may only be removed if it is considered a hazard or prevents reasonable access. All tree removals on public property must be authorized by the City. Tree removal shall be performed by a City authorized professional (T.C.C. Sec. 21-3;3). If a tree is removed and the site permits for a tree replacement, replace with the right tree in the right place (Figure 24). In the case of non-native removals, replace with a native or desert adapted species. Holes or depressions left by tree removals, unsuitable for replacement must be backfilled and leveled to match immediate surroundings.

Figure 24. Replace a non-native tree such as an Aleppo Pine with two native velvet mesquites.

5.9 Field Guide:

Prune for health:

• Deadwood

• Rubbing branches

• Included bark

• Codominant unions

• Restorative pruning

Pruning with Purpose:

• Look for horizontal clearance or space from structures

• Over walkways and pedestrian areas, 7' pedestrian clearance between ground and to the bottom of a tree canopy

• Over streets, 15' vehicle clearance between ground and to the bottom of a tree canopy

• To keep roadway signage visible and free from obstruction

• To maintain site visibility triangle

• To remove a broken or hazardous limb

Pruning tips in Tucson:

• Respect the natural form of the tree - native trees are often multi-trunked

• It is possible to prune for clearance without removing major trunks

• Less is more- over-lifting the canopy and removing all sprouts on the trunk allows for sun damage

References: ANSI-A300 (latest edition) Pruning, Arizona Department of Water Resource’s Low Water

Use/Drought Tolerant Plant list, City of Tucson Lanscape Maintenance Manual, Arizona Nursery

Association Growers Committee Recommended Tree Specifications, Storm 2 Shade GSI Field Guide

Chapter 6 Safety

Chapter 6 Safety Standards

The City shall make every effort to ensure on the job safety. The standards for job site safety are as follows:

• PPE shall be worn at all times specific to job site responsibilities

• All staff engaged in tree maintenance shall follow ANSI Z133 standards

• Adhere to City of Tucson Risk Management best practices

Chapter 6 Best Management Practices

6.1 General safety

While performing tree care, workers shall wear personal protective equipment and appropriate clothes and shoes for work conditions (Figure 25). Tools and equipment shall be in good working order, employees shall be instructed in proper and applicable use of PPE, and appropriate workplace practices in accordance with OSHA and consensus standards, including, but not limited to ANSI and ASTM.

Personal protective equipment (PPE) may include but not limited to eye protection, ear protection, respiratory protection, proper boots and attire, and hard hats shall be worn as appropriate and applicable.

Figure 25. How to dress for tree work.

6.2 Emergency procedures

All personnel engaged in arboricultural operations shall be instructed in the correct procedures for emergency response including emergency and non-emergency calls, identification and treatment of poisonous plants and insects, and appropriate CPR and first aid responses.

6.3 Job briefing and Worksite setup

A job briefing shall be conducted at the jobsite prior to beginning work. This briefing shall include the nature of the job, general safety, site specific safety, fire safety, communication protocol, utility line locations, traffic control plan, the degree of supervision required at the site, and any other site-specific needs for the workday.

6.4 Electrical Safety

Work in proximity to electrical conductors must be performed by personnel with the proper safety training and under the direction of an arborist certified by the International Society of Arboriculture. The employer shall train each employee that all overhead and underground electrical conductors, guy wires, pole grounds, and communication wires and cables shall be considered energized with potentially fatal voltages. Qualified utility personnel should be on site as necessary. Safe distances should be maintained to ensure safety regarding electrical and utility lines. Further electrical safety instructions can be found in Section 4 of the ANSI-Z133 Arborist Safety Guide.

6.5 Vehicle and Equipment Safety

Persons operating city vehicle must possess a valid driver’s license and adhere to City responsibilities regarding utilization of city vehicles. Worksite Vehicles shall be inspected and in proper working order prior to use. All safety features shall be inspected and utilized as appropriate and in accordance with manufacturer instructions. All posted speed limits and traffic laws shall be adhered to at all times.

Employees shall be properly trained in proper vehicle use, care, and safety.

Equipment shall be inspected and in proper working order prior to use. All safety features shall be inspected and utilized as appropriate and in accordance with manufacturer instructions. All posted speed limits and traffic laws shall be adhered to when towing or moving support equipment such as chippers, air compressors, light units, bobcats, lifts, etc. Employees shall be properly trained in proper equipment use, care, and safety. Situational awareness and proper clearance from other equipment, employees, utilities, and the public shall be maintained at all times.

6.6 Tool Safety

Always ensure power tools are in good working order consistent with manufacturer specifications for safe use. Employers shall provide training and instructions on proper use and care of power tools.

Appropriate PPE shall be worn at all times. Situational awareness and proper clearance from other equipment, employees, utilities, and the public shall be maintained at all times. Proper supervision, licensing, and operating instructions should be maintained when operating power tools. The correct hand tools and equipment shall be selected for the appropriate job and hand tools should be used for their intended purpose in accordance with manufacturer guidance and instructions (Figure 26).

Employers shall provide training and instructions on proper use and care of hand tools. Appropriate PPE shall be worn at all times when utilizing hand tools. Situational awareness and proper clearance from other equipment, employees, and utilities shall be maintained at all times.

Figure 26. Tools for tree care.

6.7 Climbing Safety

Climbing operations shall be conducted by certified individuals and those with appropriate experience and qualifications.