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Unearthing the ISA Arborist: Setting Apart the Tree Whisperers from the Rest

Updated: Nov 3, 2023

Trees Are Good.

You know it. We know it. He, she, they, know it.

This isn’t a secret, but sometimes it can feel like finding a reliable tree care expert can be!

You want to take care of your trees. You enjoy the cool shade in these hot California summers. You remember how your loved one planted a seed that grew with you as you worked and played and lived. Your tree speaks for your property without ever saying a word.

Ideally, our trees will outlive us.

But like every living thing, life gives and takes away.

Similarly, to doctors, who studied and trained and worked to prolong the lives of their patients, ISA Certified Arborists have dedicated their lives to preserving and maintaining the health of trees.

But how can you verify that the person you’re hiring to look after your trees is qualified?

Who Can Be an ISA Certified Arborist?

Since 1924, The International Society of Arboriculture has worked to promote the professional practice of arboriculture to foster a greater awareness of the benefits of trees.

Basically, they’re the real deal.

An ISA Certified Arborist is a person who has met the requirements set forth by the International Society of Arboriculture. These requirements include completing extensive training, maintaining, and continuously achieving educational credentials, passing examinations, and having many hours of working experience.

Additionally, they must adhere to a certain Code of Ethics that helps protect the integrity of an ISA Certified Arborist credential.

ISA Certified Arborists are knowledgeable about the best treatment practices, tree care management and are best equipped to diagnose tree health concerns.

ISA Certified Arborists v. Tree Experts, Tree Surgeons, & Arborists

A large tree

It comes down to education and certification.

If a person works on trees, they can claim to be a tree expert, a tree surgeon or even an arborist!

But unless they have completed the International Society of Arboriculture’s requirements, they cannot claim to be an ISA Certified Arborist.

Working with trees can be dangerous work! There’s no guarantee that the tree surgeon or tree expert you’ve hired has the advanced skills, knowledge and training to care for your trees in a safe way.

So How Do You Verify That You’ve Hired an ISA Certified Arborist?

Your beloved trees are getting sick.

Okay, admit it, you didn’t even know a tree could get sick until you noticed that your tree that’s usually vibrant and thriving is, well, not doing so hot.

You do a quick internet search, or maybe you’ve actually talked to someone in real life, and they recommended some guy.

Well, just some guy isn’t going to cut it.

You need a qualified specialist. Someone who you can trust knows what they’re doing.

To Verify that you’ve hired an ISA Certified Arborist:

Go to the Trees Are Good website to verify a credential. It’s important to ask the person for the ISA credential number from the person you’re considering hiring to take care of your trees.

Here, you can find all individuals currently credentialed through the ISA Credentialing Program. You can search by a person’s name or by their certification number.

Not all individuals listed are available for hire.

Having Difficulty Verifying an ISA Arborist’s Credentials?

Contact the Customer Support at the International Society of Arboriculture at

Reporting False Advertisements, or What If Someone Claims to be Certified, but Isn’t?

You’d think in the Age of Information, liars wouldn’t even try.

But here we are, and some people still think it’s okay to lie about their credentials.

All advertisements for ISA Credential Holders are required to list both the individual’s name and their ISA Certification Number.

Unsure if you’ve found a false ad?

The ISA-Arbor website recommends:

  1. Reviewing the ISA Branding and Style Guide (found on their site)

  2. Verifying an Individual’s Certification Status (using the Trees Are Good link above)

  3. Submitting the ad to their office for official review either by email, or via snail-mail to ISA, 270 Peachtree Street NW, Suite 1900 Atlanta, GA 30303 United States.

Help protect the integrity of the ISA Certification. It’s illegal for a non-credentialed individual or company to claim they’re credentialed with the International Society of Arboriculture.

About Sims Tree Health Specialists, Inc.

Sims Tree Health Specialists, Inc. is dedicated to the preservation, education, improved health, and safety of trees. Sims THS has been providing California’s Urban Forests with premium healthcare since 1972. To learn more, visit our website:

Sims THS offers services with our ISA Certified Arborists in the following:

A tree in the forest

Diagnosis and Disease Management, Pest Suppression, Organic Solutions, Fruit Suppression, Drought Protection, and Arborist Assessment Reports and Preservation Plans.

In addition to providing quality tree health services, the Sims family is known for their educational pursuits. In 1996, they started the Sims Tree Learning Center (TLC), a 6-acre botanical garden and research facility sponsored by Sims Tree Health Specialists, Inc. The facility houses multiple types of gardens including a cactus and succulent garden and one of the largest collections of Palms in the Inland Empire. Learn with us!

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