A short list
From the International Society of Arboriculture’s advice on hiring:
- Proof of insurance, and a call to the insurance company to confirm it.
- Local permits and licenses checked.
- More than one estimate, and references.
- The lowest bid weighed against the written scope and the firm’s credentials, not taken by default.
- Caution with door-to-door offers of bargains.
- Everything in writing; reputable firms use a contract.
State licenses
An industry magazine counted 24 states with some form of licensing for tree care companies in late 2025, under very different rules. Among the states this site covers, the state agencies confirm:
| State | Who licenses tree work |
|---|---|
| California | Contractors State License Board, class C-49 Tree and Palm (C-61/D-49 before 2024) |
| Louisiana | Department of Agriculture and Forestry, arborist license for paid tree work |
| Maryland | Department of Natural Resources, Licensed Tree Expert |
Elsewhere, ask the city or county about contractor licenses and rely on confirmed insurance and a written contract. Each state page says what our research found.
Credentials
ISA certification is voluntary: an exam plus continuing education, verifiable with the society’s Verify a Credential tool. It shows knowledge; it is not a license. Arborist assessment
The contract
Which trees and what is done to each, stump or no stump, who hauls the wood and chips, who repairs lawn ruts or a fence opened for access, the price, the payment terms and the date.
Checked against the sources below on 2026-10-11.
What are the warning signs a tree may fail?