Leading Consulting Arborists

for the Pacific Northwest

Leading Consulting Arborists for the Pacific Northwest

A balanced approach to tree management.

With over 40 years of experience, we provide expert consulting services for all your tree management needs. From protecting trees during development to expert witness services, our team is here to ensure your projects succeed while preserving the beauty and benefits of urban trees.

Our Services

ISA Board Certified Master Arborists 

ISA Qualified Tree Risk Assessors

ASCA Members and Registered Consulting Arborist

Meet the Team

  • Terrence P. Flanagan

    PRINICPAL, CONSULTING ARBORIST

    Recently recognized as a "True Professional" by the International Society of Arboriculture (ISA), Terry Flanagan has dedicated his life to arboriculture. As a Board Certified Master Arborist® with Tree Risk Assessment Qualification, Terry brings over 40 years of experience to Teragan & Associates. His career has included significant contributions to the industry, including pioneering tree risk assessment standards and leading innovative tree management practices.

    MORE ON TERRY

  • Peter van Oss

    SENIOR ASSOCIATE

    With a family history in horticulture, Peter van Oss has a deep-rooted passion for trees. After relocating from the Netherlands, he has built 13 years of field experience and 4 years as a consulting arborist in the Pacific Northwest. Peter is ASCA Registered Consulting Arborist #826, ISA Certified Arborist, Tree Risk Assessment Qualified, and ASCA Tree and Plant Appraisal Qualified, bringing a wealth of knowledge and enthusiasm to every project.

  • Tom Feitl

    ASSOCIATE

    Tom Feitl’s career as an arborist began in Minnesota and has since expanded to the Pacific Northwest. An avid tree climber and outdoor enthusiast, Tom combines his love of nature with his professional expertise. With 8 years in the field, Tom is an ISA Certified Arborist and Tree Risk Assessment Qualified, dedicated to preserving and understanding trees in their natural state.

OUR MISSION

Preserve, plan for, and manage trees for today’s and tomorrow’s generations.


OUR VALUES

Professional. Ethical. Pragmatic. Collaborative. Sustainable.


News & Updates