Tree services in Denver, CO

Emerald ash borer was confirmed in Boulder County in 2013 and has since spread through the Denver metro. Without treatment, ash mortality is essentially 100% within 3-6 years of arrival. Denver Forestry has been managing the city's public ash inventory through a combination of treatment (for high-value specimens worth preserving) and removal (for the rest). Private property ash is largely on the homeowner.

The practical clock for ash removal: dead ash becomes brittle within 2-4 years of canopy death. Climbers cannot rig from brittle ash safely, so the architecture shifts toward crane-assisted or sectional-from-adjacent-tree work — both more expensive than removal in the first season after death. If you have a standing dead ash on your property, the cheapest and safest time to remove it is within 12 months of visible canopy decline.

Identification: ash has compound leaves (5-9 leaflets per leaf), opposite branching, and diamond-shaped bark furrowing at maturity. D-shaped exit holes in the bark and bark blonding (where woodpeckers strip outer bark looking for larvae) are diagnostic of EAB.

Denver's semi-arid climate produces stress patterns that drive much of the local tree work:

Drought stress is chronic. Average annual precipitation is 14-16 inches, with most of it falling as snow that does not infiltrate well. Trees stressed by extended dry periods become more vulnerable to bark beetles, fungal disease, and structural failure. Supplemental irrigation through dry spells is the standard recommendation for any high-value tree.

Late spring snow events (April-May heavy wet snow) produce widespread limb failure on trees that have leafed out. Maples, ash, and honeylocust are particularly vulnerable. Pre-leaf-out structural pruning reduces failure probability.

Summer thunderstorm and microburst activity produces wind damage. June-August severe weather days routinely include 60-80 mph straight-line wind events that bring down weakened limbs and whole trees.

Wildfire smoke from Front Range and mountain fires affects tree health by reducing photosynthesis during prolonged smoke events. Trees stressed by smoke-affected summers carry forward into spring decline.

The right time for non-emergency tree work is late winter through early spring (February through April) — before the wet snow window and before the active growing season. Pre-storm prep work and pre-leaf-out structural pruning are most effective in this window.

Denver Forestry manages public trees (boulevard trees, park trees, and trees on city property) and administers tree-protection regulations. Boulevard trees are generally city property — homeowners cannot remove a boulevard tree without Denver Forestry involvement, even if it is in front of their house. The city also requires permits for certain large-tree removals on private property and for tree work tied to development.

The surrounding municipalities (Aurora, Lakewood, Westminster, Centennial, Englewood, Golden) and unincorporated Adams, Arapahoe, Denver, Douglas, and Jefferson counties each have their own ordinances. Boulder County in particular has stronger tree protections than most Denver-metro jurisdictions. Always verify the specific jurisdiction before assuming the rules.

Most Denver residential removals near power lines run through Xcel Energy line-clearance protocols. Trees touching primary lines require an Xcel crew or dispatched line-clearance contractor. Trees touching the service drop are typically handled by the private crew with documented coordination. Xcel contact happens 2-4 weeks before the work. The right sequence is contact Xcel, schedule the line work, then schedule the arborist crew the same day or next.