Which US states license arborists or tree companies

There is no national tree license in the United States. A few states license the people who do tree work, some license the business, and one licenses tree contractors through its contractor licensing board. A state missing here is not a state with no rule. This page describes what the agency pages say. It is not legal advice, and the agency decides who is covered.

One point first. An ISA Certified Arborist credential is a voluntary credential from a private body. It is not a state license. Three state pages below do name it in connection with the exam or the license, and each is quoted exactly where it comes up.

Connecticut

The state environmental agency (DEEP) says on its commercial arborist license page: "An arborist license is required for persons advertising, soliciting or contracting to do arboriculture in Connecticut." Its definition of arboriculture is work done for hire to improve the condition of fruit, shade or ornamental trees by feeding, fertilizing, pruning, trimming, bracing, treating cavities, or protecting them from insects and diseases. The license is category 3D of the commercial pesticide supervisor certification, and the licensed arborist is treated as a supervisory pesticide applicator for pesticide use.

The statute, section 23-61b on the General Assembly chapter 451 page, says the same and exempts a person who improves or protects a tree on their own premises or on their employer's property. It also lets the commissioner issue a license without an exam to a nonresident licensed under a substantially similar law in another state.

Test. A written multiple-choice exam, then an oral exam on a set date. The oral starts with tree identification, passed at 80 percent. The practical part is 10 questions, one from each of 10 categories including safety, general tree work, cabling and bracing, insects, diseases and pesticides. The page says a total of at least 70 percent and at least 7 out of 10 in at least seven categories.
Age. The supervisor certification page says an applicant must be at least 18 years of age.
Fees. US$200 for the exam and US$285 for the license after the exams are passed. The license is good for five years, then US$285 again at renewal. Renewal also asks for continuing education credits, per that page.
Business. Section 23-61h says no one may operate an arborist business without a certificate of registration, with a fee of US$240. Section 23-61j says each arborist business must employ at each place of business at least one arborist licensed under 23-61b.

New Jersey

The Board of Tree Experts says its licensing page covers two titles under an Act passed on January 16, 2010, with rules adopted on April 17, 2017: Licensed Tree Expert and Licensed Tree Care Operator. Both are earned by passing an exam and showing good moral character. The Board's page on licensing basics says: "The Act requires that at least 1 person in each company hiring itself out to perform tree care services be licensed." So the license attaches to the company's tree care, not to every worker.

Operator scope. The Board lists tree pruning, repairing, brush cutting or removal, tree removal, and stump grinding or removal.
Expert scope. Everything the operator does, plus tree establishment, fertilization, cabling and bracing, lightning protection, consulting, diagnosis and treatment of tree problems, risk assessment and pesticide application.
Exam qualifications. For the operator exam: age 18 or older, good moral character, three letters of reference, a high school diploma or GED, and three years of continuous employment in arboriculture. For the expert exam: a four-year degree in a listed field, five years of continuous employment, or two years of college plus three years of employment. The exam qualifications page has the full lists.
Fees. From the fee schedule: US$50 license application, US$100 for each written exam, US$100 for the expert field exam, US$150 for the initial two-year license and US$150 to renew, US$75 for a reciprocity application, and US$200 for the biennial business registration.

On credentials, the Board's reciprocity page says: "The Board of Tree Experts has determined that the ISA Certified Arborist (CA) credential is equivalent to the Licensed Tree Care Operator (LTCO) certification." Holders apply with the reciprocity form, a copy of the certificate and the fee. The same page says the TCIA credentials Tree Care Safety Professional and Tree Care Specialist, held together, are equivalent to the operator license.

New Jersey businesses

The Board's business page says every business providing tree care services for hire in New Jersey must register every two years, including businesses located outside the state. Among the listed requirements: at least one licensed individual working full time, general liability insurance of US$1,000,000 or a letter of credit for the same amount, workers compensation cover, and annual proof of employee safety training. Registered businesses display their NJTC number, three inches high, on at least two sides of every service vehicle. The page says civil penalties of up to US$1,000 can apply for a first violation of working without registering.

Maine

The Department of Agriculture, Conservation and Forestry says on its arborist licensing page: "Anyone performing arborist services in Maine must first obtain an arborist license." Applicants pass a test in the landscape category, the utility category, or both, and show proof of adequate insurance. For licensing purposes, arboriculture work means leaving the ground to prune or trim, installing cabling or bracing, diagnosing and evaluating trees, and felling or taking down trees in developed areas. The page says it does not include planting and fertilizing, stump grinding, chipping, or house and wood lot clearing, and that treating for pests and diseases needs a commercial pesticide applicator license.

It also says: "Licensed arborists from another state, and ISA certified arborists don't need to take the exam, but must apply for a license." There is an apprentice permit, which needs no test but is a training permit only. The permit holder works under the direct supervision of a licensed arborist. The page gives no fee.

Rhode Island

State law, section 2-19-2 of the General Laws, says anyone who wants to practise the trade of arborist must get a license from the director of the Department of Environmental Management, who may require an exam. The department's rules, part 1.3 of 250-RICR-70-00-1, say who needs the license in two cases.

Any individual who will spend any portion of their time working alone at a job site where arboriculture is done on another person's property for pay.
Where several people work at one such site, at least one must hold a license, and all must be close enough that a licensed arborist continually monitors their work.

The rules list two license types, Standard Arborist and Limited Utility Arborist. Exams are held in January, March, June and September. The pass mark is 70 percent, and the department may grant an oral exam on request. Part 1.6 of the rules adds: "At the Department's discretion, an exemption from the examination process may be granted upon proof of proficiency based on evidence of examination by an agency from another state or examination by the International Society of Arboriculture (ISA)." Fees are US$25 per exam application and US$25 per license or renewal, and licenses expire on December 31. The statute sets a fine of up to US$1,000 for violations.

Louisiana

The Department of Agriculture and Forestry says on its arborist licensing page: "Arborist licenses are required if you work on trees for a fee." The Arborist License covers recommending or carrying out tree removal, pruning, trimming, cabling, fertilization and cavity work. A separate Utility Arborist License covers removing trees or parts of trees along utility rights of way. Licenses expire each January 31. Renewal asks for proof of general liability and workers compensation insurance, continuing education, and a fee of US$125 per year. The page does not describe an exam. The Horticulture Commission is the contact on that page.

Maryland

The Department of Natural Resources says on its Licensed Tree Experts page: "A person may not engage in the work or business of a tree expert without a license issued by the Department." An employee under the supervision of a Licensed Tree Expert may not be required to hold a license in their own name. The licensee must tell the department about any company working under the license and the insurance it carries.

California

California runs tree work through its contractor board. California's contractor board said in an industry bulletin of November 13, 2023 that it created the C-49 Tree and Palm Contractor classification "to ensure tree service contractors are tested on health and safety protocols in the tree service industry," and took applications from January 1, 2024. It also says all C-49 applicants sit a trade exam whatever other classes they hold, and that holders of the older C-61/D-49 Tree Service class issued before that date may keep working under it. The C-49 definition says a Tree and Palm contractor plants, maintains and removes trees and palms, including pruning, stump grinding and guying. It says no license is required for incidental pruning by a nurseryperson or a gardener.

When a contractor license applies at all is set by a general rule. The board's what kind of contractor page says anyone who contracts for work needing a building permit, or uses employee labor, or contracts for work valued at US$1,000 or more in combined labor and materials, must hold a current license.

Cities and counties

A city can add its own rules on top of the state. New York City Parks is one example. Its Tree Work Permit page says work on or within 50 feet of a tree under City jurisdiction needs a permit before the work starts, and lists removal, pruning, stump removal and pest management among the activities. The page says the entity "must be qualified" and that the department reserves the right to deny a permit to a contractor in poor standing. That is a permit for the work, not a license for the person. Other cities and counties set their own rules.

At a glance

State	What is required	Agency
Connecticut	Arborist license by exam; business registration	Environment (DEEP)
New Jersey	Expert or Operator license; business registration	Tree Experts Board
Maine	Arborist license by exam; apprentice permit	Agriculture (DACF)
Rhode Island	Arborist license by exam	Environment (DEM)
Louisiana	Arborist license, yearly fee	Agriculture (LDAF)
Maryland	Tree expert license	Natural Resources
California	C-49 contractor class, trade exam	Contractors Board

Pesticide application has its own certification in every state, covered in the pesticide licences guide. For business set-up beyond licenses, see starting a tree service.