Thornton, CO Landscaping Rules: Tree Removal & Heritage Trees (2026)

Article III, Division 2 of Chapter 46 gives Thornton's city forester, appointed by the parks and recreation director, authority to order the trimming or removal of trees or plants on public or private property whenever the forester determines it necessary to stop the spread of disease or insects or to protect public health and safety, using standards set by the International Society of Arboriculture (Section 46-102). The code separately declares it a public nuisance for an owner to maintain a tree or plant in a condition that threatens public health and safety.

Enforcement runs through a notice-to-correct process: the forester mails a written notice to the property address (or to the owner's address on file with the county assessor if the property has none), effective on the date of mailing, giving up to 30 days to comply, though the forester can grant more time on request (Section 46-103(a)-(b)). If the property owner ignores the notice or any extension, the forester can correct the condition directly and charge the cost to the owner; unpaid invoices become a lien on the property after 30 days (Section 46-103(c)).

An owner who disagrees can file a written appeal with the city manager's office within seven days of the notice's effective date; the city manager appoints a hearing officer within five days, a hearing must occur within 15 days of the appeal, and the hearing officer's decision is final, with compliance required within seven days of that decision (Section 46-104). Where the forester finds an immediate threat to public health, safety, or public property, Section 46-105 allows entry onto private or public property to eliminate the danger right away, upon obtaining a warrant for seizure from a state court of record if no notice was mailed first; the owner retains the same appeal right afterward. Violations of a notice to correct are unlawful and punishable under Section 1-8(a) per Section 46-101.