Jurisdiction: Newbury Park is part of the City of Thousand Oaks. This means that the rules for protected trees (all oak species over two inches in diameter, plus certain landmark trees) are identical to those throughout all of Thousand Oaks.

The general principle — that selecting an ISA Certified Arborist is the wisest choice due to complex regulations — is especially applicable in Thousand Oaks.

Here is a breakdown of why this intellectual and professional standard is crucial in the City of the Oaks:

1. The City of Thousand Oaks’ Tree Ordinance is Strict

Thousand Oaks has a robust Oak Tree Preservation and Protection Ordinance that protects not just mature trees, but virtually all oak trees regardless of species, starting at a very small size.

Protected Species: All species of Oak (Quercus) over two inches in diameter are protected. Additionally, certain large California Sycamore, Black Walnut, Bay Laurel, and Toyon trees are protected as “Landmark Trees.”

Permit Required for Pruning: Any cutting or pruning of live tissue on a protected tree generally requires an Oak Tree Permit from the City. This permit is required for any work that impacts the tree or soil in its Protected Zone (5 feet beyond the dripline or 15 feet from the trunk, whichever is greater).

2. The Requirement for a Certified Arborist

While the City of Thousand Oaks’ public-facing information does not explicitly state that every single person doing the trimming must be ISA certified for a simple permit, the process for any significant work relies heavily on ISA Certified Arborists.

Tree Reports: If you are seeking a permit for removal, significant pruning, or encroachment (like construction), the City will require an Oak Tree Report that contains a thorough horticultural evaluation. These reports must be prepared by a qualified expert, which is universally an ISA Certified Arborist, to be accepted by the city.

Proof of Hazard: If a tree is deemed hazardous, a City representative may be involved, but if they cannot make a determination, the property owner is advised to retain a private consultant (Certified Arborist) to submit documentation.

General Best Practice: The foundational document for Ventura County’s wider tree ordinance states that all trimming, even if modest and not requiring a permit, must use International Society of Arboriculture (ISA) pruning practices to protect the tree’s health. Only a Certified Arborist is fully trained and certified in these scientific standards.

In essence, any tree trimmer who does not employ or work under the direct guidance of an ISA Certified Arborist is operating with a significant intellectual and legal deficit in Thousand Oaks. Hiring a certified professional ensures the work is done in a way that safeguards your valuable property asset and adheres to local law.

Read About Bob Loft, ISA Certified Arborist, here.