What Is an Arborist? Credentials, State Licenses and When to Hire One

Key takeaways

• ISA Certified Arborist candidates need 3 years of full-time experience (about 1,795 hours a year) or a degree plus 1 to 2 years, must score 76 percent on 200 questions, and recertify every 3 years with 30 CEUs (ISA Program Guide, Aug. 2025).
• ISA says its certifications “do not represent licensure.” Eight states have their own tree credential, from Maryland’s Licensed Tree Expert to New Jersey’s, which requires $1,000,000 in liability coverage (N.J.A.C. 7:3A).
• The Tree Risk Assessment Qualification now lasts 7 years, up from 5, and requires a 2-day course, a 110-question exam and a field test (ISA TRAQ Program Guide, July 2026).
• Public contracts from 2024 to 2026 bill consulting arborists at $113 to $240 an hour; Chino Hills, CA, lists arborist reports at $165.15 per man-hour (Chino Hills fee schedule, Jan. 2026).
• Work should follow ANSI A300 (consolidated 2023) and ANSI Z133-2026, and federal rules keep unqualified workers 10 feet from power lines at 50 kV or below (29 CFR 1910.333).

What does an arborist do?

An arborist cares for individual trees rather than whole forests: pruning, removal, planting, diagnosis and treatment, cabling and bracing, risk assessment and written reports. OSHA lists pruning, removal, plant health care, cabling and bracing, transplanting, consulting, fertilization and lightning protection as the services tree care companies sell. The ISA exam weights safe work practices at 15 percent and pruning at 14 percent.

Ohio State University Extension defines an arborist as “an individual trained in the art and science of selecting, planting, and maintaining individual trees” (OSU Extension, HYG-1032, March 2025). That definition carries no legal weight. Anyone can print “arborist” on a truck door; what separates a credentialed arborist is an exam, an experience requirement and continuing education, which the tables below spell out.

The clearest public map of an arborist’s skills is the content outline of the ISA Certified Arborist exam, which the International Society of Arboriculture (ISA) Certified Arborist Program Guide (revised August 2025) splits into 10 weighted domains. The weights come from a job task analysis of working arborists, so they show where the job’s time and risk sit.

Exam domain	Share of questions	What it covers on a residential job	Source
Safe work practices	15%	Climbing, rigging, chainsaw and aerial lift safety, work near power lines	ISA CA Program Guide
Pruning	14%	Pruning types and cuts, how much crown to remove, young-tree structure	ISA CA Program Guide
Tree biology	11%	How trees grow, seal wounds and store energy	ISA CA Program Guide
Tree risk	11%	Spotting defects, judging likelihood of failure and the target below	ISA CA Program Guide
Tree identification and selection	9%	Naming species, right tree for the site	ISA CA Program Guide
Installation and establishment	9%	Planting depth, staking, first-year watering	ISA CA Program Guide
Diagnosis and treatment	9%	Insects, diseases, abiotic damage, treatment choices	ISA CA Program Guide
Trees and construction	9%	Root protection zones and construction damage	ISA CA Program Guide
Soil management	7%	Soil testing, compaction, mulch and fertilization	ISA CA Program Guide
Urban forestry	6%	Street trees, inventories, municipal programs	ISA CA Program Guide

What is arborist mulch?

Arborist mulch, or arborist wood chips, is the chipped bark, wood and leaves a tree crew produces while pruning or removing trees, and many crews give it away rather than pay to dump it. Washington State University Extension found the mix resists compaction better than uniform bark or sawdust mulch and recommends a depth of 4 to 6 inches for weed control (WSU Extension FS160E, 2015).

Whether those free chips beat shredded bark is a narrower question than most pages admit: our wood chips vs mulch review sets 14 published trials side by side.

WSU also says to taper chips to almost nothing at the trunk, because mulch piled against bark keeps it wet and invites fungi; the publication is now marked archived but has not been replaced. For bed and ring sizes, our mulch calculator converts square feet and depth into cubic yards.

How is an arborist different from a tree service, tree surgeon, forester or landscaper?

“Arborist” names a person and a skill set; “tree service” names a business, which may or may not employ one. A forester manages stands of trees for timber, wildlife or watersheds, a landscaper installs and maintains planting, and “tree surgeon” is the British term that survives in U.S. law: Alabama and Mississippi still license “tree surgery.” The ASCA list of arborist types says foresters “may lack field experience with individual trees.”

Title	What it means	Who regulates it	Typical work	Source
Arborist (title alone)	A person trained in caring for individual trees; no exam is needed to use the word	Nobody, unless a state license covers tree work for hire	Pruning, removal, planting, diagnosis	OSU Extension HYG-1032
ISA Certified Arborist	Passed a 200-question exam after 3 years of experience or an equivalent; recertifies every 3 years	ISA, a voluntary program accredited by ANAB to ISO 17024	Same work, with tested knowledge	ISA
Tree service or tree care company	A business that sells tree work; it may or may not employ credentialed arborists	OSHA rules for employers; a state license in the 8 licensing states listed below	Removal, pruning, stump grinding, storm cleanup	OSHA
Tree surgeon	British term for a tree worker; in U.S. law it survives in state “tree surgery” licenses	Alabama Tree Surgery permit (ADAI); Mississippi Tree Surgery License (MDAC)	Same as a tree service	Ala. Code 2-28-1; MDAC
Consulting arborist (ASCA RCA)	An independent expert who writes reports, appraisals and testimony and usually sells no tree work	ASCA, voluntary	Risk reports, tree appraisals, construction protection plans, disputes	ASCA
Line-clearance tree trimmer	A worker trained to prune near energized power lines	OSHA, 29 CFR 1910.269	Utility right-of-way pruning	29 CFR 1910.269
Forester	Manages forests and stands for timber, wildlife or watersheds rather than single yard trees	Some states require a forester to write forest management plans; the SAF Certified Forester credential is voluntary	Management plans, timber sales	ASCA, Types of Arborists
Landscaper	Installs and maintains lawns, beds and plantings	State landscape contractor licenses in some states; California’s C-49 tree class excludes a gardener’s incidental pruning	Planting, mowing, beds, pruning shrubs and small trees	CSLB, C-49

For residential work the useful split is person versus company. A homeowner hires a company, so the questions are whether a credentialed arborist is on that crew, whether the company holds a state license where one is required, and whether it carries liability and workers’ compensation insurance. Our guide to checking a contractor license covers the lookup step for landscapers.

What do arborist certifications and credentials mean?

ISA runs seven tree credentials, and the ISA credential list as of October 2026 is: Certified Arborist, Board Certified Master Arborist, Certified Arborist Utility Specialist, Certified Urban Forest Professional, Certified Tree Climber, Certified Tree Worker Aerial Lift Specialist and the Tree Risk Assessment Qualification (TRAQ). The American Society of Consulting Arborists adds the Registered Consulting Arborist (RCA). All are voluntary and none is a license.

The table compares what each credential demands. ISA states plainly that its certifications “do not represent licensure, registration, or other authorization to practice or to conduct business activities for a fee” (ISA CA Program Guide, p. 8). A homeowner should read every credential as proof of tested knowledge, then check the state license and the insurance certificate separately.

Credential	Eligibility	Exam	Pass mark	Validity and renewal	Source
ISA Certified Arborist	3 years full-time, or degree or training plus 1 to 2 years	200 multiple-choice questions, 3.5 hours	76%	3 years; 30 CEUs plus $220, or retest	ISA, Aug. 2025
ISA Certified Tree Climber	18 months of climbing experience	65 questions in 90 minutes plus a 45-minute climbing practicum	80% written, 70% skills	3 years; 15 CEUs, CPR and first aid, aerial rescue practice, $220	ISA, Aug. 2025
ISA Certified Tree Worker Aerial Lift Specialist	18 months of experience, 6 of them operating an aerial lift	65 questions in 90 minutes plus a 45-minute lift practicum	70% written, 80% skills	3 years	ISA, Mar. 2020
ISA Certified Arborist Utility Specialist	Certified Arborist plus 2,000 hours of utility vegetation work in 2 years, or 36 months in the past 10	115 questions, 2 hours	75%	3 years; 6 CEUs plus $95	ISA, Aug. 2025
ISA Certified Urban Forest Professional	Certified Arborist, or 3 years managing urban trees, or education plus experience	115 questions, 2 hours	70%	3 years; 30 CEUs plus $220	ISA, Aug. 2025
ISA Board Certified Master Arborist	Certified Arborist plus 8 points from certification years, degrees, credentials and experience	165 questions, 4 hours; $495 enrollment	70%	3 years; 60 CEUs plus $320	ISA, May 2026
ISA Tree Risk Assessment Qualification (TRAQ)	An ISA certification, a related degree, or an approved state license	2-day course, then 110 questions in 2 hours plus a 1-hour field assessment	75% written, pass field	7 years, then retrain and retest; no CEUs	ISA, July 2026
ASCA Registered Consulting Arborist	ASCA member (5 years of experience plus degree, BCMA or 240 CEUs), Consulting Academy graduate, 420 CEUs	Two reports scored by ASCA ($100 each)	75% per report	Annual: $56 RCA fee plus $549 dues; 30 CEUs every 2 years	ASCA, Apr. 2026

1. Certified Arborist200
2. Board Certified Master Arborist165
3. Utility Specialist115
4. Urban Forest Professional115
5. TRAQ (written part)110
6. Certified Tree Climber (written part)65
7. Aerial Lift Specialist (written part)65

Source: ISA program guides (Aug. 2025, May 2026, July 2026; Aerial Lift Mar. 2020), accessed October 2026 Totals include unscored pretest questions (20 on the Certified Arborist exam). Climber, Aerial Lift and TRAQ also have a field or skills test.

Show the numbers

	Questions
Certified Arborist	200
Board Certified Master Arborist	165
Utility Specialist	115
Urban Forest Professional	115
TRAQ (written part)	110
Certified Tree Climber (written part)	65
Aerial Lift Specialist (written part)	65

Exam length tracks scope. The Certified Arborist exam has 200 multiple-choice questions in 3.5 hours with 20 unscored pretest items; the Board Certified Master Arborist exam has 165 questions in 4 hours and a 70 percent pass mark (ISA BCMA Program Guide, May 2026). TRAQ pairs a 110-question written exam with a 1-hour outdoor assessment of a real tree (ISA TRAQ Program Guide, July 2026).

How long does it take to become an ISA Certified Arborist?

At least 1 year and usually 3. ISA requires three years of full-time arboriculture experience, defining one year as about 1,795 hours, or a shorter stint combined with a degree or assessed training (ISA CA Program Guide, p. 4). The arithmetic below converts each route into field hours, the number an employer’s reference letter has to document.

Eligibility route	Field experience required	Field hours (years x 1,795)	Training hours
Experience only	3 years full-time	3 x 1,795 = 5,385	None beyond the degree
Two-year associate degree (2+ arboriculture courses)	2 years full-time	2 x 1,795 = 3,590	None beyond the degree
Four-year bachelor degree (4+ arboriculture courses)	1 year full-time	1 x 1,795 = 1,795	None beyond the degree
900 hours of assessed training (90+ in arboriculture)	2 years full-time	2 x 1,795 = 3,590	900 classroom hours
1,800 hours of assessed training (180+ in arboriculture)	1 year full-time	1 x 1,795 = 1,795	1,800 classroom hours

Fees are the second hurdle. ISA charges a $50 application fee and a $369 exam enrollment fee to non-members ($40 and $295 for members), then $220 every three years to recertify with 30 continuing education units (ISA CA Program Guide). Over the first six years that is about $859 for a non-member who never fails, before study materials or membership dues.

Cost item	Non-member	ISA member	When
Application fee	$50	$40	Year 0
Exam enrollment fee	$369	$295	Year 0
Recertification fee (30 CEUs)	$220	$220	Year 3
Recertification fee (30 CEUs)	$220	$220	Year 6
Total, first six years	$859	$775	Excludes retakes ($120 each), dues and courses

What is a Board Certified Master Arborist or a consulting arborist?

A Board Certified Master Arborist (BCMA) is an ISA Certified Arborist who has banked 8 eligibility points, earned at 1 point per year certified, 1 to 4 for a degree, 3 for being an ASCA Registered Consulting Arborist and 1 per six years of work, then passed the 165-question exam (ISA BCMA Program Guide). Recertification takes 60 CEUs every three years, double the Certified Arborist load.

A Registered Consulting Arborist writes reports, appraisals and expert opinions rather than selling tree work. ASCA requires membership (five years of arboriculture experience plus a four-year degree, BCMA status or 240 CEUs), graduation from its Consulting Academy, 420 CEUs and two reports that each score at least 75 percent (ASCA RCA eligibility, April 2026 capture; ASCA membership eligibility).

Which states license arborists or tree work?

Eight states have their own arborist or tree-work credential: Alabama, Connecticut, Louisiana, Maine, Maryland, Mississippi, New Jersey and Rhode Island. California and Hawaii license tree contractors as a class, and Minnesota requires registration with no exam. Elsewhere the title is unregulated at state level; UNH Extension notes that certification “is not required by the State of New Hampshire” (UNH Extension).

State	Credential and law	Who needs it	Exam and eligibility	Insurance	Fees and renewal	Lookup
Alabama	Tree Surgery permit, Ala. Code 2-28-1	Paid cavity filling, bracing, cabling and wound treatment; the law excludes pruning	$75 exam; written statement of training and experience	None stated for tree surgery	$175 a year, Oct. 1 to Sept. 30	ADAI
Connecticut	Arborist license, CGS 23-61b	Anyone who advertises, solicits or contracts to do arboriculture; 1 licensee per business location	Written 75%, tree ID 80%, oral practical 70%; age 18	None stated	$200 exam; $285 license valid 5 years; 12 CE credits per cycle	DEEP
Louisiana	Arborist and Utility Arborist licenses, La. R.S. 3:3804	Paid tree removal or care, or working under a licensee’s direct supervision	70% exam; ISA-certified exam option	Public liability and workers’ compensation	$150 exam; $125 license; renews by Jan. 31 yearly	LDAF lists
Maine	Licensed Arborist, 7 M.R.S. 2179	Paid arborist work, including pruning that requires leaving the ground	Written and oral, 70% (Master 75%); ISA Certified Arborists exempt from exam	$150,000 per occurrence, $300,000 aggregate	$60 exam; $30 license a year	DACF list
Maryland	Licensed Tree Expert, Nat. Res. 5-415 and 5-418	Paid care or removal of trees taller than 20 feet; supervised employees exempt	140 questions, 70% in each of 10 domains; 3 years of experience, or 2 years of college plus 1 year	Required by DNR; amount set by the Department	$30 exam; $20 renewal every 2 years; 8 CE hours (COMAR 08.07.07.07)	DNR
Mississippi	Tree Surgery License, MDAC	Only firms that advertise as licensed, bonded or insured	100 questions, 70%; 2 years of experience in the last 3, or education routes	At least $100,000	No fee; valid indefinitely	MDAC
New Jersey	Licensed Tree Expert or Tree Care Operator, N.J.A.C. 7:3A	Every tree care business; exempts ground work with no climbing, lifts or rigging and no removal of trees over 6 inches DBH	Expert: written 70% plus field 65%, 5 years or degree routes; Operator: written 70%, 3 years	$1,000,000 general liability plus workers’ compensation	$150 license for 2 years; $200 business registration; 32 CE credits per 2 years (fees)	NJBTE
Rhode Island	Arborist license, 250-RICR-70-00-1	Anyone working alone on paid arboriculture; 1 licensee on every crew site	70% exam ($25), or ISA certification	None stated	$25 a year, expires Dec. 31	DEM
California	C-49 Tree and Palm contractor, CSLB	Planting, maintaining and removing trees and palms; jobs of $1,000 or more	4 years of experience; CSLB exams	$25,000 bond	CSLB license fees	CSLB
Hawaii	C-27b tree trimming and removal, DCCA	Pruning, trimming and removing trees and stumps; jobs over $1,000 or needing a permit	Contractor licensing exams	Per contractor rules	Contractor license fees	DCCA
Minnesota	Tree care registration, Minn. Stat. 18G.07	All paid tree care, trimming or removal	None	None stated	$25 a year, expires Dec. 31	MDA
New Hampshire	No state arborist license	Not applicable	Voluntary state association certification	Not applicable	Not applicable	UNH Extension

The rules differ more than the titles suggest. Maryland’s law reaches only trees taller than 20 feet (Nat. Res. 5-415), New Jersey’s carves out ground-based maintenance, and Mississippi’s license is optional unless you advertise as licensed. Insurance floors run from none stated in Connecticut to $1,000,000 in New Jersey. Our 50-state landscaping license table covers the pesticide and contractor licenses that sit alongside these.

How do you check an arborist’s credentials?

Check three things separately: the ISA credential, the state license where one exists, and the insurance. ISA’s Find an Arborist directory verifies credential holders by name or location, but listing is voluntary, so a missing name is a prompt to ask for the ISA digital certificate, not proof of fraud. In the eight states with a tree license, the state lookup is the legal test.

1. Ask for the arborist’s full name, credential and ISA certification number, and which crew members will be on site. A company can employ one Certified Arborist and send a crew with none.
2. Look the person up in ISA’s Find an Arborist directory or the ISA certificate directory. ISA says names, credentials and digital certificates appear there unless the holder opts out (ISA CA Program Guide, Privacy).
3. Check that the credential has not expired. Most ISA certifications run 3 years and TRAQ runs 7 (ISA TRAQ Program Guide).
4. In a licensing state, search the state’s licensee lookup; the state table above links each agency. Mississippi’s list shows only firms that chose to license, because its law requires the license only for those who advertise as licensed, bonded or insured.
5. Ask for a certificate of insurance showing general liability and workers’ compensation, then phone the insurer to confirm the policy is current, as OSU Extension advises.
6. Get the scope in writing in ANSI A300 terms, and reject any bid that proposes topping or climbing spikes on a tree you are keeping (OSU Extension, HYG-1032).

One trap catches people searching “ISA credential directory”: the page at connect.isa.org belongs to the International Society of Automation, which also abbreviates itself ISA and lists cybersecurity and automation certificates. Arborist credentials live only on isa-arbor.com, treesaregood.org and ISA’s certificate directory. Insurance is the third check; our tree service insurance guide covers what a certificate should show.

What standards should an arborist’s work follow?

Two ANSI standards govern U.S. tree work: ANSI A300 for how trees are cared for and ANSI Z133 for worker safety. TCIA consolidated A300’s 10 parts into one document available from January 1, 2024, on a single five-year review cycle (TCIA). ISA reports that Z133-2026 is now approved and that the 2017 edition was effective until May 27, 2026 (ISA, Z133-2026).

Standard or rule	Current edition	What it governs	What to ask for	Source
ANSI A300 Tree Care Standards	Consolidated 2023 edition, available from Jan. 1, 2024; reviewed every 5 years	Pruning, soil, support systems, lightning protection, risk assessment and other care practices	A written specification that cites the A300 objective	TCIA
ANSI Z133 Safety and Health Requirements for Arboricultural Operations	Z133-2026; the 2017 edition was effective until May 27, 2026	Climbing, rigging, chain saws, aerial lifts, electrical hazards	A crew that follows it; ISA offers the digital standard free and print at $29.95 retail	ISA
29 CFR 1910.333(c)(3)	Current federal rule	Unqualified workers and their tools must stay 10 feet from lines at 50 kV or below, more above 50 kV	Utility or line-clearance crew for anything closer	eCFR
29 CFR 1910.269	Current federal rule	Training and work rules for line-clearance tree trimmers	Proof of line-clearance training	eCFR
ANSI A300 Part 9 (tree risk assessment)	2011 part, now inside the consolidated A300	Levels 1, 2 and 3 of tree risk assessment	The assessment level in the contract	A300 Part 9

A300 matters to a homeowner because it is how a quote should be written. TCIA says the standards “are used to develop written specifications for work assignments,” so a proposal that names the A300 pruning objective, the branch sizes and the percentage of crown to remove can be checked after the crew leaves (TCIA, ANSI A300). Our tree trimming cost guide shows how those specifications change the price.

What are the three levels of tree risk assessment?

The A300 risk standard defines three levels, and the level sets how closely the tree is examined. Level 1 is a limited visual check of many trees, Level 2 a 360-degree ground inspection of one tree, and Level 3 adds tools such as resistance drilling or sonic testing when Level 2 cannot judge a defect (ANSI A300 Part 9-2011, 93.4.2). TRAQ trains assessors in this method.

Level	What the standard requires	Typical use
Level 1: limited visual	“A limited visual assessment of an individual tree or a population of trees near specified targets” from foot, vehicle or aerial patrol	Screening street trees or a utility corridor for obvious defects
Level 2: basic	“A 360-degree, ground-based visual inspection of the tree crown, trunk, trunk flare, above-ground roots, and site conditions”; sounding with a mallet when specified	One yard tree near a house, driveway or play area
Level 3: advanced	All Level 2 work plus methods such as resistance drilling, sonic assessment, pull testing or sub-surface root assessment, used when Level 2 cannot judge a defect	Large trees with hidden decay or high-value targets

How much does an arborist cost?

No national price list exists, so we used public contracts and city fee schedules. From 2024 to 2026 they bill consulting arborist time at $113 to $240 an hour, most often $165 to $225, and cities that require arborist review charge permit applicants extra: Burlingame bills $190 an hour with a 1-hour minimum (Burlingame FY 2025-26). Tree work itself is priced per job, not per hour.

Payer and document	Role	Rate	Date	Source
Menlo Park, CA, on-call agreement proposal	Senior Consulting Arborist	$240 per hour	May 2024	Staff Report 24-084-CC
Stevenson, WA, project cost table	Senior associate consulting arborist	$225 per hour ($90 labor plus overhead and fee)	Sept. 2024	Council packet
Burlingame, CA, fee schedule	City arborist review charged to applicant	$190 per hour, 1-hour minimum	FY 2025-26	Master Fee Schedule
Escondido, CA, consultant proposal	ISA Certified Arborist, project manager	$185 per hour	Sept. 2026	Council agenda
Chino Hills, CA, fee schedule	Arborist report or risk assessment (levels 1 to 3)	$165.15 per man-hour	Jan. 2026	Table 10
Menlo Park, CA, on-call agreement proposal	ISA Certified Arborist	$113 per hour	May 2024	Staff Report 24-084-CC
Pearland, TX, tree maintenance contract	Consulting arborist line item inside a $975,698 maintenance bid	$40 per hour	March 2026	Council agenda

Why the gap between a tree worker’s wage and the bill? Stevenson’s table shows it: $90 an hour of direct labor plus 120 percent overhead and a 30 percent fee becomes $225 billed (Stevenson, WA). BLS puts the median tree trimmer and pruner wage at $24.50 an hour in May 2025 (BLS OEWS), and OSU Extension notes that trucks, booms, chippers and insurance sit in every price (OSU Extension).

What does an arborist report for a tree permit cost?

In cities that require one, the permit and review fees can rival the report itself. The arithmetic below uses published city fees and contract rates; the 2 and 4 hour report times are our assumptions for a single residential tree, so treat the totals as estimates. Cupertino’s arborist-review permit costs $386 more than its permit without review (Cupertino FY 2025-26).

Scenario	Arithmetic	Estimate
Burlingame: protected-tree application plus minimum city arborist review	$451 + (1 x $190)	$641
Cupertino: first-tree permit with arborist review vs without	$851 minus $465	$386 added by review
Private report at Chino Hills’ contract rate, 2 hours	2 x $165.15	$330.30
Private report at the Stevenson rate, 4 hours	4 x $225	$900
Saratoga: tree removal permit plus arborist review deposit	$141 + $1,000 deposit	$1,141 up front (FY 2024-25)

Prices for the work itself are on separate pages: our tree trimming cost guide, the tree removal cost guide and the stump grinding cost guide build ranges from published inputs.

When do you need an arborist, and which credential should you ask for?

Match the credential to the risk. Ground-level pruning of a small tree needs no credential; work above the ground, near power lines, on a tree that could hit a house, or for a permit, lawsuit or insurance claim does. ISA advises hiring an arborist when a tree is “dead or dying, an unacceptable risk, causing an obstruction, crowding other trees” or near new construction (ISA, Why Hire an Arborist).

If your situation is…	Do this	Why (source)
Any branch or the work zone is within 10 feet of an overhead line	Call the utility; hire only a line-clearance crew	Unqualified workers must keep 10 feet from lines at 50 kV or below (29 CFR 1910.333(c)(3))
A tree could hit a house, car, road or play area if it failed	Hire a TRAQ-qualified arborist and get a Level 2 assessment in writing	TRAQ trains the A300 risk method (ISA TRAQ guide)
You need a report for a permit, insurer, lawyer, appraisal or neighbor dispute	Hire a consulting arborist (ASCA RCA or BCMA) who will not bid the work	RCAs pass two scored reports and 420 CEUs (ASCA)
Your city requires a permit to remove a protected tree	Hire an ISA Certified Arborist or ASCA consulting arborist the city accepts, and budget for the city’s review fee	Palo Alto accepts reports from ISA Certified or ASCA registered arborists (PAMC 8.10); Cupertino charges $851 for a first-tree permit with arborist review (Cupertino FY 2025-26)
Pruning or removal needs climbing or a lift	Hire an insured company with an ISA Certified Arborist plus a Certified Tree Climber or Aerial Lift Specialist on the crew	Those credentials test climbing and lift skills in a practicum (ISA)
You live in a state with a tree license	Get the license number and check the state lookup before signing	New Jersey requires every tree care business to register and employ a licensee (N.J.A.C. 7:3A-2.1); Maine requires a license to work as an arborist for pay (7 M.R.S. 2179)
Leaves, bark or branches show disease or insects	Hire an ISA Certified Arborist; ask for lab confirmation before paying for treatment	OSU advises proof from a non-biased diagnostic clinic (OSU Extension)
Construction or trenching will come within the root zone	Bring in a consulting arborist before digging for a tree protection plan	Trees and construction is 9 percent of the Certified Arborist exam (ISA)
Small tree, hand tools, both feet on the ground	No credential needed; follow ISA pruning guidance	ISA says pruning or removing large trees “can be dangerous work” (ISA)

1. 1Is any branch or the work zone within 10 feet of an overhead power line?

   YesCall the utility. Only a line-clearance crew trained under 29 CFR 1910.269 should work there.

   NoGo to the next question

2. 2Do you need a written opinion for a permit, insurer, lawyer, appraisal or neighbor dispute?

   YesHire a consulting arborist (ASCA RCA or ISA BCMA) who will not bid the work.

   NoGo to the next question

3. 3Could the tree hit a house, car, road or play area if it failed?

   YesHire a TRAQ-qualified arborist and ask for a Level 2 assessment in writing.

   NoGo to the next question

4. 4Does the job need climbing, rigging or an aerial lift?

   YesHire an insured company with an ISA Certified Arborist plus a Certified Tree Climber or Aerial Lift Specialist on the crew, licensed if your state requires it.

   NoGo to the next question

5. 5Do leaves, bark or branches show disease or insects?

   YesHire an ISA Certified Arborist and ask for lab confirmation before paying for treatment.

   NoGround-level pruning of a small tree with hand tools needs no credential.

Source: 29 CFR 1910.333 and 1910.269; ISA TRAQ Program Guide (July 2026); ASCA RCA eligibility; OSU Extension HYG-1032

After a storm, the order matters more than the credential: stay clear of any downed or sagging line and report it to the utility, then document damage for the insurer before anything is cut. Our emergency tree removal guide covers storm pricing and insurance claims, and the tree removal cost guide covers planned removals.

What do popular guides get wrong about arborist credentials?

Several pages that rank for arborist questions repeat facts that ISA has since changed. We checked each claim below against the current ISA program guide or standard page, accessed October 2026. The most common errors are the TRAQ renewal period, which ISA extended from five to seven years, and credential names that ISA retired, such as Municipal Specialist and Tree Worker Climber Specialist.

What some guides say	Where we saw it	What the primary source says	Source
TRAQ is valid for five years	ISA Rocky Mountain Chapter TRAQ page	“The ISA TRAQ credential is valid for seven years”; then retrain and retest	ISA TRAQ Program Guide, July 2026
Credentials named Municipal Specialist and Climber Specialist	OSU HYG-1032 (March 2025); ISA RMC six certifications page	ISA now lists Certified Urban Forest Professional and Certified Tree Climber	ISA Types of Credentials
Workers “cannot attain any other ISA credential without first earning” Certified Arborist	OSU HYG-1032	Tree Climber needs 18 months of climbing; Urban Forest Professional accepts 3 years managing urban trees; TRAQ accepts degrees and state licenses	ISA Climber guide; CUFP guide; TRAQ guide
The arboricultural safety standard is “Z133.1”	OSHA tree care standards page	The current standard is Z133-2026; the 2017 edition was effective until May 27, 2026	ISA, Z133-2026
ANSI A300 is a set of separate parts	Older pages that cite A300 Part 1, Part 9 and so on	TCIA consolidated all 10 parts into one standard, available from Jan. 1, 2024	TCIA
The “ISA Credential Directory” at connect.isa.org	Search results for “ISA credential directory”	That page belongs to the International Society of Automation; arborist lookups are on treesaregood.org	ISA Find an Arborist

Is being an arborist a dangerous job?

Yes, by federal data. In 2024, 99 tree trimmers and pruners died on the job: 39 in falls and 39 from contact with objects or equipment, plus 12 from harmful exposures such as electricity (BLS CFOI, Table A-5, 2024). BLS publishes a rate only for grounds maintenance workers as a group: 20.9 deaths per 100,000 full-time workers, against 3.3 for all workers (BLS CFOI rates, 2024).

Occupation (SOC code)	Employment	Median hourly	Median annual	Source
Tree trimmers and pruners (37-3013)	55,160	$24.50	$50,960	BLS OEWS, May 2025
Foresters (19-1032)	10,430	$36.73	$76,400	BLS OEWS, May 2025
All occupations	155,495,730	$24.51	$50,980	BLS OEWS, May 2025

BLS’s handbook calls tree trimmers and pruners “also called arborists” and says “professional certification is not required” but “demonstrates competency and reliability” (BLS Occupational Outlook Handbook, Sept. 2026). It projects the occupation growing 4 percent from 2025 to 2035. For pay in the wider trade, see our landscaper salary data.

1. Falls, slips, trips39
2. Contact with objects and equipment39
3. Exposure to harmful substances or environments12
4. Transportation incidents7

Source: BLS Census of Fatal Occupational Injuries, Table A-5, 2024 97 of the 99 deaths fall in these four event groups. Exposure includes electrocution.

Show the numbers

	Deaths
Falls, slips, trips	39
Contact with objects and equipment	39
Exposure to harmful substances or environments	12
Transportation incidents	7

This page is general information, not legal or safety advice. Licensing rules, credential requirements and fees change; confirm with the state agency or credentialing body linked in each row before you hire or apply.