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.
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.
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
PERMITS
A PERMIT IS REQUIRED FOR:
Removing trees as part 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
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)
Tree function (shade, aesthetics, habitat, screening, and erosion control)
WATER-RISE
IN WATER-LIMITED AREAS LIKE WESTMINSTER:
Prioritize drought-tolerant, water-wise, and diverse species
Avoid overused types of trees for a resilient urban forest
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)
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
NEIGHBORLY TREE PLANNING
COLLABORATE WITH YOUR NEIGHBORS
Trees don’t care about our property boundaries; please be a considerate neighbor when choosing planting locations
Coordinate early with neighbors about expectations
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.
PLANTING BEST PRACTICE
A PRUNING
CALL 811 BEFORE DIGGING TO LOCATE UNDERGROUND UTILITIES.
Remove dead, broken, or crossing branches
(See Page 10 for Informed Pruning)
Improve overall form using required pruning standards (ANSI A300)
B ROOT FLARE & ROOT BALL
Set root flare level with or up to 3" above grade
Position root ball at correct height
Remove basket and burlap from sides and top
C MULCHING
Apply 3" hardwood mulch
Keep mulch 3" away from trunk
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
E STAKING & STRAPPING
Place stakes in undisturbed soil at pit edge
Use ¾–1" woven nylon or polypropylene straps
Do not use hose-and-wire or chain lock
Make a loose figure-eight around the trunk, allowing ½–1" of movement, and fasten straps to the stakes, not the trunk
THESE ACTIONS CAN SERIOUSLY DAMAGE OR KILL TREES:
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
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
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!
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
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
DBH = Trunk diameter at 4.5 ft
Roots may extend 1.5-2x tree ht.
CRITICAL ROOT ZONE
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
CHOOSE AN ISA CERTIFIED ARBORIST TRAINED IN:
Best management practices
Safe, long-term pruning techniques
Tree health, structure, and aesthetics
BENEFITS:
Reduces safety hazards
Enhances tree longevity and appearance
Protects property value
WHAT TO LOOK FOR...
VERIFY: CHECK:
ISA Certification References
Liability Insurance Online Reviews Credentials via ISA website
NEARBY CITY TREE CONTRACTORS:
The City of Westminster does not license tree care companies, but neighboring cities do: CLICK/SCAN
QR CODE FOR ISA CREDENTIALS
DENVER
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
SAVE YOUR ASH
www.westminsterco.gov/EmeraldAshBorer
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.
IPS BEETLES
Attack spruce and pine by tunneling under bark
ELM LEAF BEETLES
Defoliate and weaken elm trees
FUNGAL PROBLEMS?
LILAC ASH BORER
Damage trunks and lower branches of ash trees
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.
