Unparalleled knowledge and experience!
Roger Hartzog, Principal
Roger is an International Society of Arboriculture (ISA) Certified Arborist (WE-14586A) and ISA Qualified Tree Risk Assessor. He is an Environmental Engineer, having graduated from the University of Florida School of Forest Resources as a Natural Resources Manager and attended the School of Graduate Studies in Environmental Engineering. He served with the U.S. State Department in Central America on programs involving water resources and engineered environments. He managed the CWA Section 208 Water Quality Management Program for the State of Louisiana until accepting an Attorney General’s appointment as Executive Director of the Western States Project, a multi-state and international environmental protection program headquartered in Phoenix. He founded Tree Theory Green Assets Management consultants in 2017. Recently, he established an online service to help homeowners better manage their trees by offering economical remote tree health diagnosis and consultation as The Virtual Arborist.
Juan Barba , Certified Arborist
Juan graduated from the University of Arizona with a B.S Degree in Landscape & Environmental Horticulture. Juan is An ISA Certified Arborist, native of Tucson, with 40+ years of experience throughout Arizona and several other states. He has practiced in and instructed all facets of arboricultural & horticultural care, and is a past president of Western Chapter, ISA as well as a former chair of Trees for Tucson. For 20 years Juan provided a monthly column on professional tree climbing and desert arboriculture for the premier regional magazine, Southwest Trees & Turf. Juan Barba has been a southern Arizona Consulting Arborist since 1989.
Doug Donahue, Irrigation Systems Expert
Doug Donahue is Tree Theory's resident expert in all things to do with landscape irrigation. With more than 40 years of experience with irrigation systems, including commercial, private residential, and HOA properties, Doug has comprehensive knowledge of every type of irrigation system, all component parts and brands, and their proper functioning. He performs system inventories and audits for Tree Theory clients who want an accurate third-party independent assessment of their systems and seek recommendations on how to improve efficiency to save on water costs.
Kristen Battafarano, Horticulturist and Certified Arborist (WE-14296A)
With over 20 years as a horticultural professional in the Sonoran Desert, Kristen Battafarano brings a wide range of plant knowledge to the Tree-Theory team. In addition to managing a 30-acre desert plant nursery, Kristen has been a desert gardening instructor at the Desert Botanical Garden, landscape maintenance supervisor, landscape designer, and Plant Biologist for the National Park Service. When she isn’t evaluating the health and care of landscapes throughout the region, she enjoys growing food in her organic urban garden, which has been toured by over 600 fascinated visitors.
David Hartzog, Data and IT Systems Manager
David is Tree Theory's Manager of Information Technologies. He graduated from Arizona State University with a Bachelor's and Master's degrees in Computer Systems Engineering. He is an accomplished mobile applications developer, having created Tree Theory's proprietary field inspections and GIS-based tree inventory and mapping systems, which support all field data collection and reporting.