When it comes to tree care, not all providers have the same level of training, education, or accountability. One of the most important credentials a tree care professional can hold is certification through the International Society of Arboriculture (ISA).

An ISA Certified Arborist has met rigorous standards in education, field experience, and ongoing professional development, and that makes a meaningful difference for homeowners throughout the St. Louis area.

What Is the International Society of Arboriculture (ISA)?

The International Society of Arboriculture is a globally recognized professional organization dedicated to advancing the science and practice of arboriculture. ISA establishes industry standards, promotes research, and administers certification programs designed to ensure competency in tree care.

ISA certification is not automatic. It is earned and maintained through ongoing effort. Plant biologists, researchers and botanical professionals constantly develop new treatments, care protocols, techniques, pest controls and fertilizers for trees and ISA certified arborists are required to keep abreast of the numerous developments in tree care.

What It Takes to Become an ISA Certified Arborist

Becoming an ISA Certified Arborist requires a significant investment in both time and expertise.

1. Documented Experience or Education: Candidates must have:

• A minimum of three years of full-time, hands-on tree care experience
  or;
• A degree in arboriculture, forestry, horticulture, or a related field combined with practical experience

This ensures that certification candidates have real-world exposure before ever sitting for the exam.

2. Passing a Comprehensive Examination: The ISA certification exam covers a broad range of technical knowledge, including:

• Tree biology
• Soil science
• Pruning standards
• Tree risk assessment
• Diagnosis of pests and diseases
• Safe work practices
• Cabling and bracing
• Tree installation and establishment

The exam is designed to test applied knowledge not just theory. Arborists who successfully complete the exam and become certified are considered to be among the elites in the tree care industry.

3. Ongoing Continuing Education: Certification is not a one-time achievement.

Just as with doctors, lawyers, accountants and other professionals, ISA Certified Arborists must earn continuing education units (CEUs) regularly to maintain their credential. This ensures they stay current on:

• Emerging pests and diseases
• Updated safety standards
• New research in tree biology
• Advances in risk mitigation techniques

Without meeting these ongoing requirements, certification lapses.

How Many ISA Certified Arborists Are There?

While thousands of individuals work in tree care across the United States, only a portion have achieved ISA certification.

There are approximately 35,000 ISA Certified Arborists worldwide, with tens of thousands located in the United States. Considering the size of the country and the number of companies offering tree services, that credential remains a meaningful differentiator.

In other words, hiring an ISA Certified Arborist means you are working with someone who has met nationally recognized standards and has a deep knowledge of tree and plant science.

Why Certification Matters Especially for St. Louis Homeowners

The St. Louis area presents unique environmental challenges to trees and those providing care to trees. These challenges include:

• Heavy clay soils
• Extreme freeze-thaw cycles
• High summer humidity
• Periodic drought
• Increasing pest pressures

Proper diagnosis and treatment require knowledge of both tree biology and regional conditions.

An ISA Certified Arborist is trained to:

• Evaluate structural integrity
• Identify early signs of disease
• Recommend and perform proper pruning techniques
• Determine when removal is truly necessary
• Reduce long-term liability risks

Tree work performed incorrectly can cause irreversible damage, or create hazardous conditions that surface years later. An ISA Certified arborist can successfully treat and protect trees, in the near term and the long term.

The Long-Term Financial Impact

Working with a certified professional often saves money over time.

Improper pruning can:

• Weaken branch attachments
• Accelerate decay
• Increase storm damage risk

In addition, mistakes such as incorrect planting depth can shorten a tree’s lifespan dramatically. And misdiagnosing a pest issue can lead to unnecessary treatments, or worse, untreated structural decline.

Certified arborists are trained to approach tree care from a long-term health and risk-management perspective.

Accountability and Ethics

ISA Certified Arborists agree to adhere to a Code of Ethics. That includes:

• Providing honest assessments
• Avoiding unnecessary services
• Prioritizing safety
• Using industry-approved standards

This adds a layer of professional accountability that benefits homeowners directly in terms of tree care and peace of mind.

Choosing Qualified Tree Care in the St. Louis Area

When evaluating a tree care provider, homeowners should feel comfortable asking:

• Are you ISA Certified?
• What is your certification number?
• Do you carry proper insurance?

Professional tree care is both a science and a skilled trade. Certification ensures the science and knowledge components are present, not just the equipment.

At Hansen’s Tree Service, our team includes ISA Certified Arborists who bring technical expertise and ongoing education to every property owner we serve.

If you would like a professional tree health assessment or have questions about the condition of your trees, contact Hansen’s Tree Service today to schedule a consultation.