How to apply for a tree removal permit in Thornton, Colorado

A 5-step walkthrough drawn from Thornton's tree-protection ordinance. For the underlying DBH thresholds, protected-species list, and full fee schedule, see the city ordinance page.

Expected processing time: 3-6 weeks. Plan removal timing accordingly — emergency-tree provisions may differ.

  1. 1

    Determine if your tree is regulated

    Trees at or above 6" DBH (diameter at breast height) are regulated. Significant tree: 6 inches DBH or greater on development sites. Public trees regulated by Forestry Division regardless of size. Ash species subject to EAB management. Heritage / landmark designation: Significant Trees defined under Thornton Development Code (Landscape and Tree Preservation) at 6-inch DBH or greater on development sites trigger Tree Preservation Plan review; public trees regulated by Forestry Division regardless of size — Thornton's enhanced-protection tier in lieu of a separate heritage-tree designation.

  2. 2

    Determine who must apply

    Eligible applicants in Thornton: Property owner or authorized agent with arborist report.

  3. 3

    Prepare your assessment report

    Your assessment report must include: Tree inventory with DBH, species, condition, retention plan, mitigation plan. Required certifications: ISA Certified Arborist.

  4. 4

    Submit to the permitting department

    Submit your application and assessment report to City Development Department / Forestry. Typical processing time: 3-6 weeks. Reference the full ordinance at https://www.thorntonco.gov/.

    View the full Thornton ordinance

  5. 5

    Plan for replacement obligations

    Replacement ratio: Based on tree size and condition (typically 1:1 to 2:1). On-site replacement preferred; fee-in-lieu when infeasible.

Where to file

City Development Department / Forestry

(303) 538-7295

Other Colorado permit walkthroughs

See Colorado replacement obligations compared — how Thornton's replacement ratio ranks against the rest of the state.

See Colorado heritage criteria compared — how Thornton's designation rules stack against the rest of the state.

Compare with nearby cities

Need an arborist report for your Thornton permit?

Capture an ISA TRAQ Level 1, 2, or 3 assessment in the field and export a municipality-ready PDF that fits Thornton's required report sections. Free, no account required.

Start a TRAQ assessment