A professional arborist will belong to professional organizations like: ● The International Society of Arboriculture (ISA) ● The Tree Care Industry Association (TCIA) ● The American Society of Consulting Arborists (ASCA).  Don’t hesitate to ask for their local permits, licenses, and arborist certifications. That’s why credentials exist, to provide proof of eligibility and experience. You can find arborists and verify their credentials on the ISA and trees are good websites.