Inquire about their technique to tree health: diagnostics, soil testing, pruning requirements
https://shed-wiki.win/index.php/How_to_Pick_a_Professional_Tree_Business:_Tree_Removal,_Tree_Trimming,_and_Stump_Grinding_Fundamentals
Inquire about their approach to tree health: diagnostics, soil screening, pruning requirements, and conservation versus removal viewpoint.