Major funding provided by the Arizona Department of Forestry and Fire Management's Urban and Community Forestry Program and USDA Forest Service.

These institutions are equal opportunity providers.

Tucson Community Forest Action Plan

TUCSON

CLEAN &

BEAUTIFUL

Tucson Community Forest Action Plan First Edition, JUNE 2023, Copyright 2023 © City of Tucson

Regina Romero, City of Tucson Mayor Fátima Luna, Climate and Sustainability Advisor, Office of Tucson Mayor Regina Romero Nicole Gillett, Tucson Urban Forestry Program Manager

Community Forest Action Plan Working Group members and City of Tucson Landscape Advisory Committee members (at right)

Major funding provided by the Arizona Department of Forestry and Fire Management's Urban and Community Forestry Program and

USDA Forest Service. These institutions are equal opportunity providers.

Katie Gannon, Executive Director, Tucson Clean & Beautiful, Inc./Trees for Tucson Ann Audrey, Forest Action Plan Contractor, Tucson Clean & Beautiful, Inc.

Staff and Volunteers, Tucson Clean & Beautiful, Inc.

Tucson Community Forest Action Plan Outreach Working Group

• Antonio Ramirez, Communications Director, Ward 1 Council member Lane

Santa Cruz

• Meg Johnson, Garden District Neighborhood Association and Alvernon/Grant

Initiative

• Oscar Medina, Director, Prescott College Tucson Center

• Erick Meza, Sierra Club Borderlands program

• Nelda Liliana Ruiz Calles, Community Organizer with Regeneración

• LoriAnne Barnett Warren, Program Manager, Urban and Community Forestry, Arizona Department of Forestry and Fire Management

Tucson Community Forest Action Plan Standards Working Group

• Katie Bolger, Chief of Staff, Ward 3 Councilmember Kevin Dahl

• Ursula Schuch, Ph.D., School of Plant Sciences, University of Arizona

• Deborah Munoz-Chacon, Owner, Sonoran Oasis Landscaping

• Oscar Medina, Director, Prescott College Tucson Center

• Cori Dolan, Arizona Department of Forestry and Fire Management's Urban and

Community Forestry Program

City of Tucson Landscape Advisory Committee

• Ron van Ommeren, Chairperson, Ecologist/Wildlife Habitat Specialist, Westland

Resources

• Darbi Davis, Vice-Chairperson, Neighborhood Representative, Red Bark Design

• Nichole Casebeer, Other Representative, Tucson Clean & Beautiful

• Rebeca Field, Landscape Architect, Kimley-Horn: Planning and Design

Engineering

• Alison Meadow, Urban Planner/Architect, UA—Arizona Institutes for Resilience

• Jennifer Moscato, Neighborhood Representative, Wheat Design Group

• Flor Sandoval, Water Conservation Specialist, Sonoran Environmental Research

Institute

• Kasy Schug, Horticulturist/Arborist, Tucson Electric Power

• Nick Shipley, Business Community, Civano Wholesale Nursery

• Committee Coordinator, Irene Ogata, Urban Landscape Manager, Tucson

Water, Conservation and Stormwater Resource

Additional thanks Thanks to the City of Tucson staff and to community members who contributed their valuable time to assist this process, provide guidance and review the draft Tucson Community Forest Action Plan.

Acknowledgements 2

Introduc)on 4

Ac)on 1. Value and preserve Tucson’s community forest 8

Ac)on 2. Plant trees to increase shade equity throughout Tucson 10

Ac)on 3. Grow trees with harvested water to conserve drinking water 11

Ac)on 4. Carefully posi)on trees to meet tree and site needs 15

Ac)on 5. Grow healthy trees using best prac)ces for plan)ng, watering and care 18

Ac)on 6. Choose climate resilient trees and understory plants 24

Ac)on 7. Increase tree supply to meet plan)ng goals 33

Ac)on 8. Address City of Tucson tree-related policies, standards and codes 35

Ac)on 9. Engage all Tucsonans in plan)ng trees 38

Appendix A. Addi)onal resources 41 Appendix B. Suggested climate resilient tree and shrub species for Tucson 42

Contents 3

Goal and contents of the Tucson Community Forest Action Plan

Tucson’s community forest includes all trees

• Our shared community forest includes trees at home sites, parks, businesses and all other areas

The need for community forest management

• The City of Tucson, with support from the Arizona

Department of Forestry and Fire Management, seeks to increase tree-based climate resilience by expanding forest management to address heat island conditions, heat-vulnerable neighborhoods and ways to support trees while conserving drinking water supplies

• The Tucson Community Forest Action Plan serves as a master plan to maintain Tucson's existing urban forest and expand the tree canopy to increase shade equity for underserved neighborhoods and grow a more climate resilient community forest for all Tucsonans

The Forest Action Plan helps guide all Tucsonans

• The Plan is designed to guide the City of Tucson, its partners and all Tucsonans as we work together to expand and care for our shared community forest

Contents of the Forest Action Plan

• The Plan sets out nine action categories and associated tasks along with providing additional background information and descriptions of techniques

• Appendix A lists links to additional information

• Appendix B lists suggested climate resilient species of trees, tree/shrubs and smaller shrubs for Tucson

Your tree—and every tree—is an important part of Tucson’s shared community forest.

Tucson’s community forest is made up of trees growing at home sites, apartment complexes, schools, libraries, office complexes, shopping malls, parks, along streets, in open spaces and all other locations in Tucson

4Introduction

At a %me when we need shade most, Tucson’s tree canopy coverage is far below na%onal goals—and dispropor%onate across the City

Tucson has low tree canopy coverage

• American Forests recommends 15% tree canopy coverage for desert ci7es

• Tucson averages only 6% tree canopy coverage

• Some neighborhoods have less than 2% tree canopy coverage

Urban heat island condi%ons

• In urban areas with low tree canopy coverage, accumulated hea7ng of large expanses of rooDops, streets, parking lots (“hardscape areas”) and bare soil can increase heat island condi7ons

• The elderly, young children and low income popula7ons are par7cularly at risk to the impacts of heat island condi7ons

• Heat island condi7ons can result in:

• Higher temperatures both day and night

• Higher electric use and costs for indoor cooling

• Air pollu7on caused by increased power genera7on and forma7on of ground-level ozone

• Impacts to human health and comfort including discomfort, respiratory problems, heat cramps, heat exhaus7on and heat stroke

Tucson is one of the fastest warming cities in the U.S.

– Climate Central, 2022

Urban heat island conditions occur when the sun heats large expanses of rooftops, streets, parking lots (“hardscape areas”) and bare soil. Taking good care of existing trees and planting new trees in these areas provides much-needed shade and cooling.

5Introduction

The Tucson Tree Equity Score map illustrates disparities between Tucson neighborhoods. Neighborhoods colored red and orange have low Tree Equity Scores. These are high priority areas for planting additional trees.

Source: climateaction.tucsonaz.gov/pages/milliontrees-tree-equity

Differences in Tree Equity Scores are related to disparities that make it harder for people to buy, plant and care for trees

Tucson Tree Equity Scores show disparities

• The Tucson Tree Equity Score map shows accumulated disparities in:

• Income

• Employment

• Race

• Age distribution

• Urban heat island severity

• Neighborhoods shown in red and orange on the map have low Tree Equity Scores

• The Tree Equity Score map can be viewed at:

climateaction.tucsonaz.gov/pages/milliontrees-tree-equity

Low Tree Equity Score areas are high priority tree planting areas

• Increased tree planting is urgently needed to address long-standing disparities in areas with low tree equity scores

• Increasing tree canopy coverage will help mitigate urban heat island conditions and lead to healthier and more comfortable neighborhoods

Areas of Tucson that have high heat island conditions frequently also have low Tree Equity Scores.

TREE EQUITY SCORE

6Introduction

The City and its partners are leading the implementation of the Forest Action Plan, starting with high priority planting areas

Mayor Romero’s Tucson Million Trees Initiative

• The goal of Tucson Mayor Regina Romero’s Tucson Million Trees Initiative is to promote the planting of one million trees in Tucson by 2030, starting in the frontline and low-income communities most impacted by climate change, extreme heat and environmental degradation

City of Tucson (COT) Storm to Shade Program

• The Storm to Shade program (S2S) uses Tucson Tree Equity Scores to prioritize projects that capture, clean and infiltrate stormwater to grow trees that provide shade, cooling and other benefits

COT Urban Forestry Program

• Work conducted under the Urban Forestry Program includes implementing the Tucson Million Trees Initiative and the Forest Action Plan, preparing tree planting and care guidelines and overseeing other tree-related efforts and activities

Tucson Clean & Beautiful, Inc. (TCB)

• TCB is a nonprofit organization that partners with the City in developing outreach materials, training youth to plant and care for trees and organizing tree planting events in high priority planting areas

“Trees connect us. They connect us to the Tucsonans of the past and of future generations who will sit in the shade we plant today.”

- Mayor Regina Romero

Trees are placed in a high priority planting area as part of the Storm to Shade (S2S) Program

Mayor Regina Romero plants a tree as part of the Tucson Million Trees Initiative

The City’s Urban Forestry Program oversees tree-related activities

Tucson Clean & BeauRful (TCB) staff members conduct on-the-ground training and tree planRng in partnership with the City

7Introduction

SHADE AND COOL

SUPPLEMENT FOOD SUPPLIES

PROVIDE WILDLIFE HABITAT CAPTURE STORMWATER

CALM URBAN ENVIRONMENTS BUILD SOIL, CONTROL EROSION

ENHANCE COMMUNITY SPACES

SEQUESTER CARBON

Task 1.1 Utilize the benefits urban trees provide

Shade and cool Tucson

• Trees shelter people, land, wildlife, vehicles, buildings and streets from strong sun and heat

Calm urban environments

• Trees calm traffic, increase air quality and have a soothing visual presence that improves urban conditions Build soil and control erosion

• Tree roots—along with leaf litter and soil moisture under trees—build soil, support soil life and reduce erosion

Enhance community spaces

• Trees enhance gathering areas, providing shade and comfortable settings for people to gather

Beautify urban areas

• Tree canopies, leaves and flowers, along with the birds, insects and wildlife they attract, beautify Tucson

Supplement urban food supplies

• Trees supply edible fruits, nuts, seeds and pods to provide people with local food resources

Provide wildlife habitat

• Trees, shrubs and other plants provide pollen, nectar, food, nesting sites and shelter for wildlife

Sequester carbon

• Trees bind carbon in trunks, branches and roots, both in life and in the materials later made from their wood

Capture stormwater runoff

• Tree basins intercept stormwater flows, reducing flooding and improving the quality of stormwater runoff

BEAUTIFY URBAN AREAS

The best time to plant a tree was 20 years ago.

The second best time is now.

Action 1. Value and preserve Tucson’s community forest 8

Task 1.2 Protect and maintain exis4ng urban trees

Preserve healthy trees

• When possible, design sites around healthy trees rather than removing the trees

• When possible, do not pave over a tree’s root zone

Help trees through drought and extreme heat

• If a tree show signs of stress during drought and extreme heat, water the tree deeply at and near the tree canopy dripline—especially large, mature trees that may be suscep>ble to harsh condi>ons

Protect trees from injury

• Injury makes trees vulnerable to insect and disease threats

• Protect trees from damage caused by trimmers, construc>on ac>vi>es, vehicle impacts and other sources of injury

Tend to unhealthy trees

• If trees look unhealthy, contact tree experts for advice on how to return trees to good health

COT/TCB: Promote proper tree care

• Provide resources for professionals and the public on best prac>ces for tree care

• Address correct plan>ng, watering, pruning and other tree-care topics

Adapt site design to preserve healthy trees in place Help trees through drought and extreme heat

Tend to unhealthy treesProtect trees from injury

The fastest way to increase shade in Tucson is to take good care of existing trees so they live longer and grow larger.

Water at and near the tree canopy drip line

Action 1. Value and preserve Tucson’s community forest 9

Task 2.1 COT: Develop strategies and timelines to plant one million trees by 2030

Develop a strategy to reach 15% canopy coverage in high priority planting areas

• Determine how, where and when to plant sufficient trees in high priority planting areas to grow to provide an average 15% canopy coverage

• Address tree planting at residences, school yards, commercial sites, along streets, in parking lots and in other locations

Determine a schedule to plant one million trees by

• Develop a strategy and schedule that specifies annual tree planting numbers and locations to reach the million tree planting goal by 2030

Expand the tree-planting strategy past 2030 to reach 15% canopy coverage throughout Tucson

• Develop a strategy and schedule that specifies annual tree planting numbers and locations to reach an average 15% canopy coverage throughout Tucson after the 2030 goal is reached

Temperatures under trees can be 25 degrees lower than above nearby blacktop.

- U.S. Department of Energy

Planting three new trees at this site will achieve the 15% tree canopy coverage goal once the trees are full grown, providing shade and comfort and lowering electric bills

Planting even more trees at this site will create more shade and comfort and will lower energy bills further

Prioritize tree planting on the northeast, north and northwest sides of buildings for maximum summer shade

Action 2. Plant trees to increase shade equity throughout Tucson 10

Task 3.1 Harvest stormwater to grow trees

Shape passive water harvesting basins

• Dig and shape basins, swales and other depressions in the soil to harvest direct rainfall plus stormwater runoff—rain that reaches the ground

Make gaps in curbs to harvest stormwater runoff

• Obtain city permits to work within a city right of way to cut curbs and harvest street runoff to support trees planted along the right of way (Appendix A)

• Create gaps in curbs within parking lots to allow stormwater runoff into adjacent planting basins

Use “permeable paving" to maintain flat surfaces while infiltrating water into soil

• Permeable paving includes porous concrete, paving blocks that have gaps, and other porous materials

• Plant trees within or adjacent to permeable paving

Design large stormwater basins to support trees

• Place trees on raised planting areas within or next to large basins that collect stormwater runoff so the stormwater can support tree growth while plant roots and soil bacteria help filter the stormwater

Design new and redeveloped commercial properties to use runoff to support landscape

• Comply with the City’s Commercial Rainwater

Harvesting Ordinance and Development Standard (Appendix A)

Street runoff flows through curb cut

Tucson Water delivers ≅ 30 million gallons of water a year, while calculations show ≅ 200 million gallons of rain fall over the same land area in an average year.

Gaps in curbing allow parking lot runoff into tree basin

Permeable paving allows water to infiltrate at base of tree Trees growing next to a large stormwater basin

Basin with berm Basin in street medianRainstorm over Tucson

Action 3. Grow trees with harvested water to conserve drinking water 11

Task 3.2 Harvest rooftop runoff in tanks to support trees

Install tanks (also called cisterns) to supplement passive water harvesting

• First shape soil to passively harvest water in basins

• Install tanks if more harvested water is needed

• Deliver tank water to plants via gravity flow through a hose, or install a pump to provide pressurized flow

Select tanks that fit specific site needs

• Sizes range from 50 gallons to thousands of gallons

• Materials include metal, plastic, fiberglass and reinforced concrete—some have plastic liners

• Tanks can be round, oval and even square

Design tanks to serve multiple functions

• Water stored in a tank heats up and cools off slower than the surrounding air, so nearby plants receive extra summer cooling and extra winter warming

• Tanks can be trellis structures, visual barriers, fire barriers, decorative elements and serve other functions

Apply for a Tucson Water tank rebate, if applicable

• In order to conserve potable water, Tucson Water provides a rebate to customers who install tanks (Appendix A)

Tanks constructed in series collect runoff from a large roof

Runoff from a one-inch rainfall over a 1200 square foot roof can fill a 1000-gallon tank.

Tank collects water from solar-paneled roof Tank reduces hot and cold extremes for nearby trees

Tanks come in many materials and sizes

Action 3. Grow trees with harvested water to conserve drinking water 12

Task 3.3 Develop systems that use gray water to support tree growth

Use only gray water, not “blackwater”

• Gray water is generated from washing machines, baths, showers and bathroom sinks

• Water from toilets and kitchen sinks is considered

“black water” and should not be reused without significant additional treatment

Follow guidance on the use of gray water

• Tucson Water and the Arizona Department of

Environmental Quality provide guidance on how to safely use gray water to support plants (Appendix A)

Use stormwater to dilute gray water in soils

• Gray water contains salts, soaps and other materials originating from indoor water use

• Harvest stormwater runoff in the same basins where gray water is applied to help maintain soil quality and benefit plants

Apply for a Tucson Water gray water system rebate, if applicable

• To help conserve potable water, Tucson Water provides rebates to customers who install gray water systems (Appendix A)

The use of recycled water can yield a savings of over 10,000 gallons of potable water per year!

– Tucson Water

Valves control gray water discharge to the landscape

City of Tucson Residential Gray Water Information Guide

Arizona Department of Environmental Quality (ADEQ) Using Gray Water at Home Guide

Homeowner manages gray water valves

Action 3. Grow trees with harvested water to conserve drinking water 13

Task 3.4 Harvest water that condenses in air conditioners and other cold-producing machines to support trees

Identify condensate sources at a site

• Water vapor condenses to form liquid water on cold surfaces inside cold-producing machines—the higher the humidity, the more water condenses

• Air conditioners produce condensate water in the months they operate

• Ice machines, drinking fountains and other chilling machines operate and produce condensate water year round

Determine how to intercept condensate streams

• Locate condensate water drain pipes for chilling machines and determine if/how a hose or pipe could be attached to intercept and direct the water

• Ensure the condensate harvesting hose or pipe cannot be kinked or blocked, since backing up water could damage the chilling machine

Deliver condensate directly to soil or store water in a tank for later use

• Deliver condensate water directly to water harvesting basins when convenient

• Consider storing condensate water in a tank to make the timing and location of water delivery more flexible

When weather is humid, air conditioners produce large volumes of free condensate water.

San Antonio, Texas, promotes large-scale harvesting and use of condensate water (Appendix A)

Graphs compare monthly rain (above) to production of condensate water (below). Air conditioning condensate volume is highest when air conditioners are running during hot humid months.

30 gallons/day of condensate is produced at this Tucson residence in the humid month of August

A shady landscape at the University of Arizona College of Architecture and Landscape Architecture (CALA) is supported with a combination of harvested air conditioning condensate and rooftop runoff water

Source: wrrc.arizona.edu/sites/wrrc.arizona.edu/files/Glawe%20UA%20Condensate%20Powerpoint.Nov-12-14.pdf

AcOon 3. Grow trees with harvested water to conserve drinking water 14

Task 4.1 Select and place trees based on their water needs and the availability of harvested water

Provide all trees with harvested water

• At a minimum, all low, medium and high water use trees should be positioned in or next to water harvesting basins to collect rainfall and stormwater runoff

In areas where stormwater is the only water harvesting supply, plant low water use trees

• Stormwater harvested in public rights of way, street medians, parking lot planters and other locations away from buildings can support low water use trees

• Always construct overflow structures when harvesting large volumes of stormwater

Plant medium and high water use trees close to buildings to provide additional harvested rooftop runoff, tanked water, gray water and condensate water

• Medium and high water use trees typically need a reliable water supply year round

• Place these trees near houses and buildings where multiple water harvesting supplies are available, including some year-round supplies

Providing trees with harvested water can increase canopy size and density, making Tucson shadier.

Position low water use trees (lighter colored trees) throughout the urban landscape and support them by harvesting direct rainfall and stormwater runoff. Position medium and high water use trees (darker colored trees) close to houses and buildings to provide them with additional rooftop runoff, tanked water, gray water and condensate water.

Shady landscape of low water use trees is supported by stormwater runoff from a large roof and parking lot

Action 4. Carefully position trees to meet tree and site needs 15

Task 4.2 Select and posi3on trees based on their poten3al mature size

Find out how large different tree species could grow and place them where they have sufficient space to reach their full size (Appendix B)

• Place medium and large species far enough from buildings, walls, traffic corners and other obstruc8ons to allow growth to maturity without requiring severe tree pruning

• Never plant medium or large species under or near overhead u8lity lines

• If space is limited, select small or slender species whose mature size will fit in the available space

Provide con3nuous shade where needed by carefully posi3oning trees closer together

• If there is sufficient harvested water and other supplemental water to support grouped trees, they can be spaced so their canopies eventually grow to slightly touch one another to create con8nuous shade

Plant only small stature trees or tree/shrubs if shade is needed under u3lity lines

• Carefully monitor plant growth to see if branches grow anywhere near overhead u8lity lines

• If branches grow near u8lity lines, hire a licensed, u8lity tree trimmer to safely do the pruning

Plant the right tree in the right place.

Creosote shades sidewalk under utility lines

Eucalyptus canopies join, providing continuous shade

Large palo verde growing under utility lines requires heavy pruning

Young palo verde tree has space to grow

Mature palo verde tree has adequate space in parking lot

Large mesquite provides abundant shade over street

Ac8on 4. Carefully posi3on trees to meet tree and site needs 16

Task 4.3 Understand Tucson’s sun angles to select and place trees for desired levels of shade

Note sun positions as seasons change

• In deep summer, the sun rises in the northeast and sets in the northwest (red line on drawing), heating the north sides of Tucson buildings for long hours

• In deep winter, the sun rises in the southeast and sets in the southwest (light yellow line on drawing), warming the south sides of buildings

Place trees on all sides of buildings if maximum cooling is the goal

• Plant trees northeast, north and northwest of buildings for maximum summer shade

• For moderate winter shade, plant trees that drop leaves in winter (deciduous trees) southeast, south and southwest of buildings

Do not plant trees where they will block winter sun if winter heating and/or solar panel use are needed

• Do not plant trees southeast, south and southwest of buildings if buildings have south-facing rooftop solar panels or if gaining winter heat and light in south-facing windows is desired

• It is still important to plant trees northeast, north and northwest of buildings for summer shade

Lower electric bills by planting trees in key locations to shade houses and other buildings.

For moderate winter sun, plant deciduous trees south of house

For maximum winter sun, do not plant trees south of house

Action 4. Carefully position trees to meet tree and site needs 17

Task 5.1 Before plan1ng, shape the basins and other water harves1ng structures that will support trees

Shape appropriate water harves1ng basins and other structures for sites and trees

• Water harves*ng structures include microbasins, large basins, swales, terraces, curb cuts and others

• The larger the “catchment area” that drains toward a basin, the more water storage capacity is needed

• Shape overflow structures to discharge surplus water in large storms

Before digging, get u1li1es marked and obtain necessary permits

• Before digging in a public right of way (ROW):

• Call 811 or go to arizona811.com to request that underground u*li*es in the ROW be marked

• Check plant setbacks for underground u*li*es

(Appendix A)

• Obtain a ROW work permit (Appendix A)

• Before digging on private property, hire a private u*lity loca*ng service to mark buried lines

• Dig carefully and stop if you encounter u*lity lines

Be careful digging around exis1ng trees

• Avoid disturbing exis*ng tree roots, which will likely extend beyond the tree canopy

• If you must dig, ensure exis*ng trees are well watered first

“Plant the water before you plant the tree.”

- Brad Lancaster, Rainwater Harvesting for Drylands and Beyond

Basins adjacent to path intercept stormwater runoff

Terraced basins move stormwater down a slope

Planting basins intercept stormwater runoff from sidewalk

Shallow swale harvests stormwater from parking lot

Deep swale harvests stormwater runoff from parking lot

Action 5. Grow healthy trees using best practices for planting, watering and care 18

Task 5.2 Place trees within or adjacent to water harvesting basins based on how each tree species tolerates inundation

Minimize water inundation for all trees

• Design and construct water harvesting basins to infiltrate water quickly into the soil

• Many desert trees can be placed within basins on raised mounds or terraces (Appendix A)

• Trees planted on raised areas within basins will experience minor, short-term inundation in large storms, but water will quickly drain into the soil below where roots can access it

• Do not plant trees in the bottoms of basins

Prevent inundation of trees whose trunks have a low tolerance for exposure to standing water

• Position trees that require very well-drained soil next to, rather than within, basins (Appendix A)

• Roots of trees planted next to basins will grow under the basins to access soil moisture

Some trees don’t like to grow in saturated soil—place these where they will grow best.

Roots of tree planted next to a curb cut basin grow to access soil moisture under the basin

Roots of trees positioned next to a long stormwater harvesting swale grow to access soil moisture under the swale

Trees can be positioned on raised mounds within basins, raised terraces within basins, or adjacent to basins above the water inundation level where tree roots can grow under the basin to access soil moisture

TOP

ABOVE

BASIN

TERRACE

WITHIN

BASIN

TERRACE

WITHIN

BASIN

MOUND

WITHIN

BASIN

TOP

ABOVE

BASIN

OPTIONS FOR

TREE POSITIONS

Action 5. Grow healthy trees using best practices for planting, watering and care 19

Task 5.3 Plant trees at the correct depth in well-drained planting holes

Dig the planting hole

• Once the water harvesting basin and raised mound or terrace have been shaped, dig the tree planting hole the same depth as the tree’s root ball and two or three times the width of the root ball

Check the planting hole for proper drainage

• Fill the planting hole with water—if it drains within

12 hours or so, proceed with tree planting

• If not, break up, fracture or dig through caliche or other impeding layers to improve drainage

Take the tree out of the pot, check for bound roots, then plant the tree

• Gently loosen or cut bound roots on sides and bottom of root ball so roots can grow naturally outward

• Place the tree in the hole, placing the top of the root ball even with the surrounding soil level

• Placing a tree too high in the planting hole will expose sensitive roots to dry air

• Placing a tree too low in the planting hole will expose tree bark to excessive wetting

• Backfill the hole and gently press the soil around the roots

• Water the tree right after planting

“The way you plant a tree can affect the tree’s health and growth for its entire life.”

- Katie Gannon, Tucson Clean & Beautiful

Check drainage in water harvesting basins and tree planting holes. If water is slow to drain, dig down to punch a hole through and/or fracture obstructing layers.

Ideally, holes should drain within 12 hours.

A newly dug basin filled with runoff water during a rainstorm provides an opportunity to observe how fast it drains. Once planted, roots penetrate the bottom of basins and speed up the rate of water infiltration.

Action 5. Grow healthy trees using best practices for planting, watering and care 20

Gently loosen or cut bound roots on sides and bottom of root ball so roots can grow naturally outward

Place the root ball in the planting hole at the same level as surrounding soil, backfill and gently press soil around roots

Task 5.4 Mulch trees to reduce evaporation and retain water in the soil

Apply organic mulch to improve soil health

• Apply organic mulch to reduce evaporation, insulate soil temperature and decompose to enrich soil and encourage beneficial soil life

• Place just 1 inch of organic mulch in basins that receive only direct rainfall to allow rainfall to penetrate to the soil below

• Place 2 inches of organic mulch in basins that receive both direct rainfall and stormwater runoff, since runoff can flow under mulch to the soil below

• Keep organic mulch several inches away from tree trunks to avoid excess moisture around trunks

• Replenish organic mulch periodically until trees are large enough to drop sufficient organic material to provide their own mulch

Apply rock mulch if organic mulch is not feasible

• Apply 1 to 2 inches of rock/gravel if it is not feasible to use organic mulch

• Rock will not decompose to improve soil health but will generally stay in place except in fast flows

• Rock mulch gets hot in the sun until trees are big enough to shade the rock underneath them

• Do not use decomposed granite (DG) that contains fine particles since DG sheds clay particles that can plug soil pores, reducing water infiltration

Average evaporation over open water in Tucson is more than 100 inches/year. This is almost 10 times higher than Tucson’s average annual rainfall.

Organic mulch is placed in the bottom of a large swale; the tree in the center is planted on a raised mound

As trees and understory plants grow, they increasingly self mulch by dropping leaves, flowers, pods, seeds and twigs into basins below, naturally replenishing the organic mulch layer

Desert willow flower/leaf/pod mulch Foothill palo verde flower mulch Blue palo verde seed/leaf mulch

Action 5. Grow healthy trees using best practices for planting, watering and care 21

Task 5.5 Develop a watering strategy that relies on using harvested water supplies first to conserve potable water supplies

• Water newly planted trees for two or three years to establish them, tapering off watering frequency over ;me

• Water to a depth of 12 to 18 inches to saturate the root ball and root zone

• Provide addi;onal watering aAer trees are established based on tree species, ;me of year, rainfall, temperature and other factors

• AAer establishment, provide trees with periodic deep watering if they show signs of stress in hot dry months

• Water established trees deeply under and around the canopy dripline rather than at the trunk

Trees planted from pots need two or three years of watering to become established.

Once rain stops, water with air conditioner condensate if it is available

If rain, condensate and gray water are not available, water with tank water

Whenever it rains, harvest rainfall and stormwater runoff in tree basins; fill rainwater tank if present

If condensate is not available, water basins with gray water

If no harvested water supply is available, drought tolerant, low water use trees can go without water for a period of time—observe trees closely to decide if/when to water

If it becomes necessary to water trees to preserve tree health, shade or aesthetics, use potable water during times of heat and drought

To reach more roots, water established trees deeply under and around the canopy dripline (the outer border of the tree canopy) rather than at the trunk

Action 5. Grow healthy trees using best practices for planting, watering and care 22

Task 5.6 Prune trees only when necessary to meet specific goals

Keep trees healthy by minimizing pruning

• Unpruned or minimally pruned trees have abundant leaves that fuel growth, thick tree canopies that provide deep shade and broad canopies that deflect drying winds

• Extreme pruning diminishes these benefits and can weaken trees

Follow guidelines for correct pruning if pruning is needed

• Prune only the parts of trees that are dead, damaged or in the way

• Wait several years before pruning newly planted trees to allow branch tip hormones to stimulate root growth

• Do major structural pruning in late winter to avoid fungal infections and give trees time to seal wounds before it gets hot

You can cut a branch off a tree, but you can’t put it back on the tree, so think carefully before you prune.

A well-pruned foothill palo verde tree retains the tree’s natural form

Heavily pruned foothill palo verde casts very little shade and tender bark is exposed to the sun

A well-pruned velvet mesquite tree retains the tree’s natural form

Heavily pruned velvet mesquite has few leaves leE to fuel growth

Action 5. Grow healthy trees using best practices for planting, watering and care 23

Task 6.1 Plant climate resilient trees and understory plants together to maximize shade, cooling, beauty and other benefits

Select plants native to the Sonoran, Chihuahuan and Mojave Deserts to increase the number of sun, heat and drought tolerant species in Tucson

• Appendix B lists species of climate resilient trees, tree/shrubs and smaller shrubs from southwest deserts and nearby areas, and provides information about their size and water use

Plant trees to provide the primary shade and cooling for a range of Tucson land use areas

• Six large, long-lived, low water use, climate resilient tree species are highlighted on the following pages to illustrate their characteristics and placement

• Additional highlighted species illustrate the many shapes, sizes and colors of desert trees

Select understory species to plant along with trees to increase urban benefits

• Understory plants include tree/shrubs, smaller shrubs, grasses, flowers, vines and other plants that can grow under full-sized trees

• Understory species shade the ground, provide color and diversify urban wildlife habitat

• Highlighted understory plants show the wide variety of their characteristics

Choose from a rich palette of climate resilient trees and understory species to shade and cool Tucson for years to come.

Action 6. Choose climate resilient trees and understory plants 24

Suggested planting areas ü Residential buildings (single, multifamily) ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 15 to 30 feet or more

• Width 15 to 30 feet or more

• Sonoran Desert native

• Broad canopy, multitrunk form

• Abundant lavender flowers in May

• Full shade all year except for thinning leaves in May-June

• Drought deciduous

• Very long lifespan—1000 years or more

• Edible seeds

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

PARK: Desert ironwoods can live a thousand years or more. Large old tree in full May bloom shades picnic table, supports wildlife and anchors soil in Pima County park.

PARKING LOT: Curb cuts allow runoff water into planting area

RESIDENTIAL SITE: Ironwood tree shades south side of house

NON-RESIDENTIAL SITE: Windows of medical building provide view of ironwood tree canopy

TRANSPORTATION CORRIDOR: Tree planted among porous pavers in street median is supported by stormwater runoff during rainfall events

SCHOOL SITE: Large tree shades southeast side of school building

Desert ironwood Olneya tesota

Action 6. Choose climate resilient trees and understory plants 25 ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 15 to 30 feet or more

• Width 15 to 30 feet or more

• Sonoran Desert native

• Broad canopy, multitrunk form

• Abundant cream/yellow flowers in spring

• Full shade in spring, summer and fall

• Winter deciduous—filtered shade in winter

• Long lifespan—200 years or more

• Edible seeds and pods

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

RESIDENTIAL: Velvet mesquite tree in flower attracts pollinators and casts deep shade

GATHERING PLACE: Velvet mesquite placed in the context of Tucson’s “old west” heritage

PARKING LOT: Well-pruned velvet mesquite with broad canopy casts deep shade over hot asphalt parking lot

NON-RESIDENTIAL SITE: Velvet mesquite preserved in place by constructing raised planter at original soil level

TRANSPORTATION CORRIDOR: Tree planted in wide right of way casts deep shade over adjacent street

SCHOOL SITE: Tree shades children’s play area

Velvet mesquite Prosopis velu@na

Action 6. Choose climate resilient trees and understory plants 26 ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 15 to 25 feet

• Width 15 to 25 feet

• Sonoran Desert native

• Broad canopy, multitrunk form

• Abundant bright yellow flowers in spring

• Full shade in spring, summer and fall

• Winter deciduous—dense branch/twig structure casts shade in winter as well

• Long lifespan—200 years or more

• Edible seeds

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

NON-RESIDENTIAL SITE: Multitrunk form of young foothill palo verde is retained in well-pruned tree at medical building complex

RESIDENTIAL SITE: Self-seeded, mature foothill palo verde trees incorporated into residential landscape

PARKING LOT: Young tree pruned for car access; curb cut harvests stormwater

TRANSPORTATION CORRIDOR: Foothill palo verde planted in water harvesting basin casts deep shade even in winter

WILDLIFE HABITAT: Row of palo verdes along neighborhood street supports wildlife

Foothill palo verde Parkinsonia microphylla

PARKING LOT: Spring bloom beautifies parking lot

Action 6. Choose climate resilient trees and understory plants 27 ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 10 to 25 feet

• Width 10 to 25 feet or more

• Sonoran Desert native

• Very broad canopy, multitrunk form

• Cream colored flowers in spring

• Full shade in spring, summer and fall

• Winter deciduous—filtered shade in winter

• Long lifespan—100 years or more

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

PUBLIC GATHERING PLACE: Mature catclaw acacia at church site casts deep shade over gathering place

NON-RESIDENTIAL SITE: Mature catclaw acacia in preserved desert habitat at the University of Arizona

RESIDENTIAL SITE: Catclaw acacia with ample room to grow to mature size

PARKING LOT: Young catclaw supplied with stormwater through curb cut

TRANSPORTATION CORRIDOR: Catclaw in street median, pruned for traffic

Catclaw acacia Senegalia greggii

TRANSPORTATION CORRIDOR: Major pruning needed on large catclaw growing under power lines

Action 6. Choose climate resilient trees and understory plants 28 ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 10 to 30 feet

• Width 15 to 30 feet

• Sonoran Desert native

• Adaptable canopy shape, multitrunk form

• Long flowering season with white, pink, violet or purple flowers

• Many cultivars are available with varying flower colors

• Full shade in spring, summer and fall

• Winter deciduous—filtered shade in winter

• Long lifespan—150 years

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

NON-RESIDENTIAL SITE: Desert willow and naQve understory plants grow in stormwater harvesQng landscape at Tucson Ward 6 office

PUBLIC GATHERING PLACE: Desert willow shades wide sidewalk at the University of Arizona

RESIDENTIAL SITE: Dense canopy shades south side of house

PARKING LOT: Large tree casts shade in summer

TRANSPORTATION CORRIDOR: Row of desert willows in tree median water harvesting basins

SCHOOL SITE: Young tree will grow to shade school play yard

Desert willow Chilopsis linearis

Action 6. Choose climate resilient trees and understory plants 29 ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Where not to plant

• Under utility lines

Characteristics

• Height 20 to 40 feet or more

• Width 15 to 40 feet

• Chihuahuan Desert native

• Broad dense canopy

• Multitrunk and single trunk forms

• Evergreen—provides dense shade all year long

• Long lifespan—50 to 150 years

• Supports urban pollinators and wildlife

Water needs

• Low water use

• Provide establishment watering

• For maximum growth and shade, provide harvested rainfall and stormwater

RESIDENTIAL SITE: Large Texas ebony tree at residential site casts large expanse of deep shade and has ample room to grow

PARK: Row of Texas ebony trees growing in raised planter

NON-RESIDENTIAL SITE: Low maintenance Texas ebony trees shade office complex

SCHOOL SITE: Texas ebony trees shade south side of school building

Texas ebony Ebenopsis ebano

PARKING LOT: Row of well pruned Texas ebony trees grow in wide planting area adjacent to parking lot

AcWon 6. Choose climate resilient trees and understory plants 30

A sample of additional climate resilient low water use trees

A sample of climate resilient medium water use trees adapted to southwestern heat

Feather tree, Lysiloma watsonii

Guajillo, Acacia berlandieri

Blackbrush acacia, Acacia rigidula

Palo blanco, Acacia willardiana

Canyon hackberry, Cel6s re6culata

Blue palo verde, Parkinsonia florida

Palo brea, Parkinsonia praecox

Arizona rosewood Vauquelinia californica

Texas olive Cordia boissieri

Action 6. Choose climate resilient trees and understory plants 31

Other tree suggestions Suggested planting areas ü Residential buildings (single, multifamily) ü Non-residential buildings ü School sites ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Low water use tree characteristics

• Sonoran and Chihuahuan Desert natives

• Heat and drought tolerant

• Range of canopy shapes, sizes and colors

• Multitrunk and single trunk forms

• Support urban pollinators and wildlife

• Water supplies once established: harvested rainfall and stormwater runoff

Medium water use tree characteristics

• Sonoran and Chihuahuan Desert natives

• Heat tolerant, with adaptive responses in drought

• Range of canopy shapes, sizes and colors

• Multitrunk and single trunk forms

• Support urban pollinators and wildlife

• Water supplies once established: harvested rainfall and stormwater runoff; supplement throughout the year with gray water and condensate water

Appendix B lists the size ranges and water use of these and other climate-resilient tree species

Ac#on 6. Choose climate resilient trees and understory plants

Low water use understory plant suggestions

Understory plants include tree/shrubs, smaller shrubs, grasses, flowers, vines and other plants that grow under trees

Suggested planting areas ü Residential buildings (single, multifamily) ü Non-residential buildings ü Parks and other public gathering spaces ü Transportation corridor planting areas ü Parking lots

Understory placement

• Under trees in water harvesting basins

• Adjacent to water harvesting basins

• Under utility lines—especially tree/shrubs that can be pruned into small trees to provide needed shade

Characteristics

• Sonoran, Chihuahuan and Mojave Desert natives

• Multistemmed forms and cacti forms

• Colorful flowering and seeding cycles

• Range of shapes and sizes

• Range of leaf coloration

• Support urban pollinators and wildlife

Water supplies once established

• Harvested rainfall and stormwater runoff

Appendix B lists size ranges and water use for climate resilient tree/shrub and smaller shrub species

Example climate resilient tree/shrub species that can be shaped into small trees for shade

Many additional climate resilient understory plants grow well in Tucson

Jojoba bush, Simmondsia chinensis Desert hackberry, Celtis pallidaCreosote bush, Larrea tridentata

Pink fairy duster Calliandra eriophylla

Whitestem paperflower Psilostrophe cooperi

Fishhook barrel cactus Ferocactus wislizenii

Task 7.1 COT: Coordinate with public, private, commercial and wholesale nurseries to develop the necessary tree stock to plant a million trees

Establish tree-growing infrastructure

• Establish cost-effective practices to supplement tree stock for planting on government-owned land

Coordinate with wholesale plant growers

• Provide information about suggested climate resilient species to wholesale growers to promote increased production of these species for purchase by commercial nurseries, nonprofit organizations and other large-volume customers

Coordinate with commercial nurseries

• Provide suggested species lists, Forest Action Plan planting goal information and public outreach materials to commercial nurseries and nursery trade groups to assist them in providing diverse climate resilient trees and provide tree-related information to customers

Coordinate with area utilities

• Coordinate with Tucson-based utilities that provide trees to customers to give them species lists and assist them as needed to increase distribution of climate resilient trees

Tucson will need hundreds of thousands of young potted trees to plant a million trees by 2030.

33Action 7. Increase tree supply to meet planting goals 33

Task 7.2 COT/TCB: Provide guidance and support for grass roots efforts to increase tree supplies

Provide guidance on se>ng up DIY nurseries

• Develop and provide guidance on how to set up do-it-yourself nurseries using seeds collected from climate resilient tree species

Promote planCng trees from seed

• Develop and provide guidance on how to plant the seeds of climate resilient trees in the ground to grow trees that have deep healthy roots

Provide guidance on supporCng “volunteer” trees in good locaCons

• Develop and provide guidance on how to support volunteer tree seedlings that are growing in appropriate loca8ons by providing harvested water and mulch to support tree growth

• Address whether to prune or remove volunteer trees that are growing in unsuitable loca8ons such as under u8lity lines, too close to roads or buildings or blocking traffic visibility

Many climate resilient trees sprout easily from seed, both in pots and in the ground.

Blue palo verde seed pods, seeds that have been scarified and soaked prior to planting, and dry seeds Healthy volunteer foothill palo verde tree

Catclaw acacia volunteer causing a site visibility problem—this tree needs to be pruned or removed

Group of volunteer blue palo verde trees growing in an appropriate location

Action 7. Increase tree supply to meet planting goals 34

Task 8.1 COT: Update internal City tree-related policies, standards, best prac;ces and trainings

Review current tree-related prac;ces

• Consult with staff across all departments regarding their current tree-related prac6ces

• Review exis6ng job descrip6ons, workflow, standard opera6ng procedures, best prac6ces and training protocols related to trees

Prepare internal Tree Standards and Best Prac;ces

• Develop City of Tucson Tree Standards and Best

Prac6ces—address tree selec6on, plan6ng, watering, care, removal and other tree-care topics

• Revise exis6ng job descrip6ons, workflow, procedures, prac6ces and training protocols to be consistent with Tree Standards and Best Prac6ces

• Apply Tree Standards and Best Prac6ces to work conducted by City staff and City contractors

Develop City of Tucson tree-care workforce

• Prepare staff training materials based on Tree

Standards and Best Prac6ces

• Train current and new staff to develop a tree-care workforce; conduct on-going training of workforce members to keep tree-care prac6ces up to date

City of Tucson staff and contractors have an important role in caring for

Tucson’s community forest.

Tree-care professional pruning upper canopy of tree at Reid park—a highly technical job

Action 8. Address City of Tucson tree-related policies, standards and codes 35

Task 8.2 COT: Update City tree-related codes and develop a…