2026 Tree Manual

2026

TREE

MANUAL PLANT SMART. MANAGE RESPONSIBLY. STRENGTHEN OUR CITY’S CANOPY.

W W W.WE STMIN STE RCO.GOV/FORE STRY

INTRODUCTION & PURPOSE The City of Westminster has been recognized as a Tree City USA since 1986, reflecting a longstanding commitment to urban forestry. With a current tree canopy cover of 11%, the City aims to increase it to 14% by 2050.

Achieving this goal will require both public and private efforts, particularly residents planting and maintaining trees on private property. Urban trees provide significant social, environmental, and economic benefits, including improved air quality, reduced stormwater runoff, energy savings, increased property values, and enhanced mental and physical well-being.

The City of Westminster Forestry Team proudly manages 19,500 public trees. Together with more than 165,000 private trees, the city’s urban forest is a growing investment in Westminster’s green infrastructure.

CLICK/SCAN QR CODE FOR URBAN FOREST MANAGEMENT PLAN

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Tree success depends on proper care, species diversity, and protection during construction.

Residents play a vital role in selecting droughttolerant species, maintaining tree health, and ensuring long-term urban forest sustainability.

Together, the City and its community can foster a thriving, resilient urban forest that benefits current and future generations.

CONTENTS CITY RULES & SUPPORT 04 Key Ordinances & Responsibilities 05 City Tree Classification

CHOOSING & ESTABLISHING TREES 06 Tree Selection 07 Proper Tree Spacing 08 Planting Best Practices 09 Watering Guidelines

ONGOING TREE HEALTH & MAINTENANCE 10

Informed Pruning

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Tree Removal

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Harmful Practices to Avoid

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Hiring a Certified Arborist

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Common Tree Pests

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Resources & Contact

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KEY ORDINANCES & RESPONSIBILITIES In Westminster, City ordinances recognize trees as essential green infrastructure because they improve air quality, manage stormwater, lower energy use, strengthen neighborhood character, and contribute to public health. To protect these benefits, the City outlines clear responsibilities for the care of both public and private trees, ensuring consistent and responsible stewardship across the community.

Residents must follow arboricultural best practices when caring for trees!

THE FOLLOWING ACTIONS ARE PROHIBITED: Topping trees (cutting tree crown back to stubs) Damaging, pruning, or removing public trees (in parks, medians, or open spaces) without City approval 4

PERMITS AN ODP COMPLIANCE PROCESS IS REQUIRED FOR:

emoving trees as part R of large scale property development projects A permit is NOT required to prune trees located entirely on private property, but we strongly encourage hiring an ISA Certified Arborist to perform tree work.

If a tree grows near a property boundary and its trunk crosses into public space, it is potentially a public tree.

Always verify ownership with the City’s Forestry Team before conducting work on trees with questionable ownership.

CLICK/SCAN QR CODE FOR CODE OF ORDINANCES

CITY TREE CLASSIFICATION TREES IN WESTMINSTER ARE CLASSIFIED INTO THREE CATEGORIES: PUBLICLY OWNED & PUBLICLY MANAGED Trees in parks, open spaces, and City facilities are maintained by the City

PUBLICLY OWNED BUT PRIVATELY MANAGED Most street trees, located in the public right-of-way (ROW), are owned by the City but maintained by adjacent property owners

PRIVATELY OWNED & MANAGED Trees fully located on private property are the responsibility of the property owner The City’s Tree Manual and Landscape Regulations offer additional guidance on proper tree care. Because the urban forest is a shared resource, residents help sustain its health and long‑term benefits. For the most current regulations and updates, residents can visit the City of Westminster’s website: www.westminsterco.gov/Forestry 5

TREE SELECTION A tree’s long-term success and ability to thrive depend on careful planning before planting.

RIGHT TREE, RIGHT LOCATION BASE LOCATION CHOICE ON THE FOLLOWING:

Site conditions (soil, hardiness zone, sun requirements, crown and root space)

BUYING A TREE Look for visible root flare Avoid trees with pests, disease, or poor pruning Know the stock type: bare root, ball and burlap, or containerized

Tree function (shade, aesthetics, habitat, screening, and erosion control)

NEIGHBORLY TREE PLANNING

WATER-WISE

Trees don’t care about our property boundaries; please be a considerate neighbor when choosing planting locations

IN WATER-LIMITED AREAS LIKE WESTMINSTER:

Prioritize drought-tolerant, water-wise, and diverse species Avoid overused types of trees for a resilient urban forest

COLLABORATE WITH YOUR NEIGHBORS

Coordinate early with neighbors about expectations

CONDITIONS ABOVE & BELOW BE SURE TO CONSIDER:

Space above and below ground to avoid conflicts with structures or power lines Soil conditions (i.e. pH, nutrients, and compaction) 6

CLICK/SCAN QR CODE FOR FRONT RANGE TREE RECOMMENDATION

PROPER TREE SPACING BOOSTS GROWTH TAKE THE TIME TO PLAN THE BEST PLACE TO PLANT:

RE-LEAF WESTY TREE SALE The City of Westminster Forestry Team offers trees best grown and selected for the region. Purchase through Re-Leaf Westy Tree Sale in February for pick up in April.

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Click/Scan QR Code for Planting Program

PLANTING BEST PRACTICE CALL 811 BEFORE DIGGING TO LOCATE UNDERGROUND UTILITIES.

IT’S FREE, EASY AND REQUIRED BY LAW!

A

PRUNING

E

STAKING & STRAPPING

Remove dead, broken, or crossing branches (See Page 10 for Informed Pruning)

Place stakes in undisturbed soil at pit edge

Improve overall form using required pruning standards (ANSI A300)

Do not use hose‑and‑wire or chain lock

B

ROOT FLARE & ROOT BALL

Set root flare level with or up to 3" above grade Position root ball at correct height

Use ¾–1" woven nylon or polypropylene straps

Make a loose figure‑eight around the trunk, allowing ½–1" of movement, and fasten straps to the stakes, not the trunk

A

Remove basket and burlap from sides and top C

MULCHING Apply 3" hardwood mulch Keep mulch 3" away from trunk

E

Create a minimum 4' mulch ring D

PLANTING PIT

Backfill with excavated soil Build a 2–4" mulch saucer around pit Slope and loosen pit sides; avoid digging in saturated soil

C B

D

THESE ACTIONS CAN SERIOUSLY DAMAGE OR KILL TREES: 8

Striking the base with mowers or string trimmers, applying herbicide to suckers, piling mulch against the trunk, and attaching by nailing or screwing into the bark.

REMOVE STAKES AFTER 1 SEASON!

Watering Guidelines FIRST 3-5 YEARS CRITICAL FOR ROOT DEVELOPMENT:

Apply 5–10 gallons/week in summer and during dry stretches year round, including winter Water slowly to avoid runoff, watering bags are very effective Use soaker hoses or low-flow sprinklers to prevent water repellency Check soil moisture: optimum soil texture should feel like a wrung-out sponge

MATURE TREES Requires infrequent but more thorough watering During droughts (May–Sep), provide 10 gallons per inch of trunk diameter

WINTER TREE CARE Wrap young or thin-barked tree trunks in burlap or commercial tree wrap. Remove wraps in spring to avoid disease and girdling the trunk

SNOW CARE Gently brush snow off branches (don’t shake frozen limbs) Avoid piling snow against trunks or root zones Avoid applying de-icing products under trees

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INFORMED PRUNING Proper pruning supports strong, healthy trees and long‑term stability.

Early pruning should be minimal, while ongoing care requires skilled, natural‑growth‑focused techniques. Working with a Certified Arborist and avoiding harmful practices helps trees thrive and adds lasting value to the property and environment.

RECOMMENDED PRUNING TECHNIQUES Crown cleaning: Remove dead, diseased, or weak branches Crown thinning: Increase air/light flow (mainly for hardwoods) Crown raising: Clear space over paths/ roads while preserving balance Crown reduction: Reduce size without damaging structure

FIRST 1-2 YEARS Only remove dead, broken, malformed, or diseased branches Avoid cutting branches over 1" in diameter

AFTER 2-3 YEARS Begin shaping the permanent structure REMOVE...

Competing leaders Suckers Rubbing or weakly attached branches Space branches ideally 18–24" apart Avoid pruning during bud break For flowering trees, prune after blooming REMOVE HERE AT THE EDGE OF COLLAR

VISIBLE COLLAR

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Tree Removal REMOVAL MAY BE NECESSARY IF A TREE IS: Dead or hazardous Structurally unsound A noxious/invasive species EXAMPLES:

Russian olive Tree-of-heaven Siberian elm

TREE RISK INDICATORS TO WATCH FOR Dead limbs or major dieback Cavities or decay in trunk/ root base Cracked soil and recent lean Co-dominant stems or unbalanced canopy Fungal growth, oozing sap or insect droppings Visible root damage or instability

HEALTHY‑LOOKING TREES CAN STILL FAIL SUDDENLY, ESPECIALLY IN STRONG WINDS! 11

HARMFUL PRACTICES TO AVOID THESE PRACTICES CAN COMPROMISE TREE HEALTH: TOPPING Cutting back to stubs Weaken structure Increase pest and disease risk

SOIL COMPACTION Avoid soil compaction and damage within the Critical Root Zone (CRZ), the area extending 1.5' from the trunk per inch of trunk diameter measured at 4.5' above ground

DBH = Trunk diameter at 4.5 ft

Example: 20"×1.5'=30' radius (CRZ) Root damage is a major but often overlooked cause of tree decline

LION'S TAILING Removing too many interior branches Causes poor weight distribution and limb breakage Reduces photosynthesis capacity

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CRIT

ICAL RO OT ZO NE

Roots may extend 1.5-2x tree ht.

HIRING A CERTIFIED ARBORIST ARBORICULTURE IS HIGH-RISK—LEAVE DANGEROUS TASKS TO THE PROFESSIONALS! HIRE AN INTERNATIONAL SOCIETY OF ARBORICULTURE (ISA) CERTIFIED ARBORIST FOR: Work near power lines Large tree pruning or removal

TRAINING

WHAT TO LOOK FOR...

CHOOSE AN ISA CERTIFIED ARBORIST TRAINED IN: Best management practices

VERIFY:

CHECK:

ISA Certification

References

Liability Insurance

Online Reviews

Safe, long-term pruning techniques Tree health, structure, and aesthetics

Credentials via ISA website

BENEFITS: Reduces safety hazards Enhances tree longevity and appearance Protects property value

NEARBY CITY TREE CONTRACTORS: he City of Westminster does not license tree T care companies, but neighboring cities do:

CLICK/SCAN QR CODE FOR ISA CREDENTIALS

The City of Westminster does NOT endorse any of the companies listed.

DENVER

LAKEWOOD 13

COMMON TREE PESTS Trees are a vital part of Westminster’s urban landscape, but their health is threatened by pests, diseases, and structural risks. Homeowners and property managers play a crucial role in spotting early warning signs and knowing when to involve a Certified Arborist. Staying informed helps preserve the safety, beauty, and longevity of our urban canopy.

EMERALD ASH BORER Destroys ash trees and poses a major threat across North America

www.westminsterco.gov/EmeraldAshBorer

SAVE YOUR ASH The City of Westminster Parks, Recreation & Libraries provides public information on the Emerald Ash Borer (EAB), an invasive pest that kills ash trees and threatens the community’s urban forest. Our outreach helps residents identify EAB, understand risks, and take steps to protect local trees.

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IPS BEETLES Attack spruce and pine by tunneling under bark

LILAC ASH BORER Damage trunks and lower branches of ash trees

ELM LEAF BEETLES

Defoliate and weaken elm trees

Learn more: www.csfs.colostate.edu/Forest-Management

FUNGAL PROBLEMS? Fungal diseases and pest infestations often occur when trees are stressed, especially from overwatering or drought. Waterlogged soil deprives roots of oxygen and encourages fungal growth, while drought or poor soil weakens trees and reduces their natural defenses, making them more vulnerable to insects and other pests.

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CONTACT US City Forester

303.658.2287

W W W.WE STMIN STE RCO.GOV/FORE STRY