TCIA accreditation or ISA certification: which one answers your question?

An ISA Certified Arborist is one named human being. TCIA Accreditation is granted to a company, and to each of its locations separately. A certified arborist can leave on Friday and take the credential with them; an accredited company keeps its status only while it keeps passing TCIA's checks, which include having the required number of arborists on staff.

That is why the two are not rivals. Certification tells you what one person knows. Accreditation tells you how the business around that person is run: whether it is insured, whether its safety and training are written down, and whether customers come away satisfied. If you already know what the ISA letters mean, the detail is in the credential guide; this page is about the other half.

The Tree Care Industry Association describes accreditation as a third-party consumer confidence verification program. A company enrols, works through a checklist that measures it against industry standards and business practice, and is audited. Accreditation then runs for three years, with a renewal check-up every year.

• Insurance

  TCIA checks that the company is properly insured, at enrolment and again at each annual renewal.

• Safety and training

  Documented safety and training programmes, measured against state and federal safety regulations.

• Licences

  Applicable business and pesticide licences, according to TCIA's own consumer guidance.

• Staff

  The required number of arborists on staff, confirmed at renewal.

• Customers

  Customer satisfaction practices and a good consumer satisfaction rating.

Note what is on that list and missing from any individual credential: insurance. A certified arborist can be uninsured. An accredited company has shown TCIA its cover within the last year. You should still ask for the certificate yourself, sent by the insurer, and know what the policy should cover.

The candidate needs three years of full-time experience in arboriculture, or a shorter stretch combined with a qualifying degree. They then sit a 200-question multiple-choice exam in 3.5 hours, across ten domains. Safe work practices is the largest single domain at 15% of the questions, ahead of pruning at 14%. To keep the credential they earn 30 continuing education units over each three-year period, or retest. ISA's program is itself accredited by the ANSI National Accreditation Board against ISO 17024.

How the credential compares with a skilled climber who holds nothing is covered in ISA certified arborist vs tree trimmer.

For anything you will rely on in writing, start with a first-pass risk assessment of your own, so you know what to ask the arborist to confirm.

ISA credentials are listed in ISA's public Spotlight Directory, searchable by name. Holders can set their profile to private, so a missing listing is a reason to ask ISA directly, not proof of a false claim.

For accreditation, use the accredited-company search on TCIA's site or call the Accreditation department on 800-733-2622. TCIA publishes a list of companies that have claimed accreditation they do not hold, and it posts a public notice for a year when a company's accreditation is involuntarily terminated.

TCIA also runs the Certified Treecare Safety Professional (CTSP) programme, which it calls the industry's only individual safety credential, with more than 3,000 holders across the U.S., Canada and Mexico. One route in is three years of field experience, including at least one year carrying responsibility for safety. A CTSP on the crew is the person who should be able to answer every question in our chainsaw safety and PPE guide.

TCIA says the programme was tested with small companies and that its cost is related to company size; fees are set out on the application, not quoted here. The case for it is commercial. Accredited firms are listed on TCIA's site and may use the logo, and TCIA pitches the process as a way into municipal bid work. If you are still at the first-truck stage, get the insurance and the written safety programme right first, as laid out in how to start a tree service; both are on the list an audit works through.