Nelda Matheny is the Managing Horticultural Consultant for Hort Science | Bartlett Consulting. As an international leader in arboriculture, she specializes in tree evaluation and management, problem diagnosis, and landscape suitability assessment.  Nelda's expertise lies in tree preservation during land development, appraising tree risk, site evaluation, and recycled water use in landscaping.  She holds a B.S. in Plant Science and an M.S. in Horticulture from the University of California, Davis, is a Board Certified Master Arborist (WE-0195B), ISA Qualified Tree Risk Assessor and a Registered Consulting Arborist (#243).


Nelda is coauthor of five books including Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines and Trees and Development: A Technical Guide to Preserving Trees During Land Development which are used worldwide as a standard for successful tree preservation.  She presents lectures and training programs on arboriculture, horticulture, and urban forestry throughout the U.S., Canada, Europe, and Australia.  Nelda has received numerous awards, including the Alex Shigo Award for Arboricultural Education, is highly recognized by the International Society of Arboriculture (ISA), and is an ISA Qualified Trainer for adult training in classroom environments.


View Nelda's curriculum vitae.  You can reach her on LinkedIn or at



Dr. James Clark is the Managing Consulting Arborist for Hort Science | Bartlett Consulting and is an internationally renowned arborist. He has twenty years of technical, research, and practical experience in tree risk assessment, tree preservation, and urban forest planning and management.  Jim developed a model of sustainable urban forest management, is experienced in designing and implementing field research, and frequently serves as an expert witness.  He holds a B.S. in Plant Science and an M.S. in Horticulture from Rutgers University, and a Ph.D. in Plant Physiology from the University of California, Davis, is a Certified Arborist (WE-0846), an ISA Qualified Tree Risk Assessor, and a Registered Consulting Arborist (#357).  Prior to joining HortScience in 1991, he was a faculty member at the Center for Urban Horticulture at the University of Washington and a professor at Michigan State University.


Jim is coauthor of four books including A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas and Trees and Development.  He has published over 30 articles in scientific journals including Arboriculture & Urban Forestry (formerly, Journal of Arboriculture), Journal of the American Society of Horticultural Science, Arboricultural Journal and Journal of Environmental Horticulture, and lectures in arboriculture and urban forestry worldwide.  Jim received the Alex Shigo Award for Arboricultural Education and is recognized internationally by the ISA.


View Jim's curriculum vitae. You can reach him on LinkedIn or at



John Leffingwell specializes in urban forestry management, site and resource evaluation, and risk assessment.  John is particularly experienced in reforestation planning, windthrow potential analysis, and urban-wildland interface management.  Prior to joining HortScience, Inc. in 2003, John worked as an urban and utility forester.  John is a Board Certified Master Arborist (WE-3966B), Registered Consulting Arborist (#442), has a California Department of Agriculture Qualified Applicators License (QAL 105129), and is an ISA Qualified Tree Risk Assessor.  His educational background includes a B.S. in Biology from California State University, Humboldt and an M.S. in Forestry from the University of California, Berkeley.


View John's curriculum vitae.  You can reach him on LinkedIn or at


Deanne Ecklund comes to HortScience with a strong technical background in horticulture, tree preservation, and tree risk assessment. She has experience in both landscape architecture and design and is familiar with all aspects of landscape management from design and installation to maintenance and construction oversight.

Prior to joining HortScience, Deanne was an arborist for the City of Palo Alto where she specialized in tree preservation and protection during residential and commercial development projects.  She helped manage the integrated pest management program for the City's trees.

Deanne is a Certified Arborist (WE-9067A) and ISA Qualified Tree Risk Assessor. She is proficient in AutoCAD.

 View Deanne's curriculum vitae.  You can reach her at

Maryellen Bell has 20 years of experience, with a strong background in agronomy, soil assessment, site development and horticulture management.  Maryellen is a well-rounded horticultural consultant focusing on diagnosis, management and use of recycled water in landscapes. 
Her passion for integrated pest management originated from her Texas State certified organic farmer roots.  Maryellen’s diverse background includes teaching high school and college horticulture in both a federal prison and campus settings. She had the opportunity to practice agriculture at Disney’s California Adventure, where farming was highlighted at Bountiful Valley Farm and Golden Vine Winery.  Prior to joining HortScience, Maryellen was Landscape Manager for Irvine Company.
Maryellen is a Landscape Contractor (#962141), holds a qualified applicators license (#105777), and a pest control advisor license (#119955) with the State of California.  She is a certified landscape irrigation auditor (#90897) with the Irrigation Association and an International Society of Arboriculture Certified Arborist (WE-5643A).

View Maryellen's curriculum vitae.  You can reach her on LinkedIn or at

Darya Barar specializes in urban forestry management with 14 years of experience in the municipal setting. She has particular experience managing trees after a severe windstorm, developing urban forestry management plans, and managing the day to day operations of a city’s urban forest.  Darya has extensive experience working with community groups, state and local agencies to implement tree grants, plans and projects.  Darya is skilled at successfully managing, planning, implementing forestry programs, from day-to-day management to long-term planning and prioritization. 
Darya is a Certified Arborist (WE-6757A).  View Darya's curriculum vitae.  You can reach her on LinkedIn or at

Ryan M. Gilpin is a consulting arborist, experienced in all phases of tree preservation on a variety of different projects.  Additionally, Ryan specializes in a growing number of environmental services at HortScience, including Best Management Practices for wildlife in arboriculture.  Ryan’s strengths include strenuous field work, large data set analysis and GIS mapping.  Ryan has a M.S. in International Nature Conservation and a B.S. in Environmental Biology and Management.

Ryan is a Certified Arborist (WE-10268A), TRAQ qualified, Wildlife Aware, Wildlife Protector (#624), and produces HortScience's GIS maps.


View Ryan's curriculum vitae.  You can reach him on LinkedIn or at


Jane Whitcomb specializes in tree evaluation, particularly field evaluation of tree health and structure.  She designs and implements production of survey maps, tree reports, and other graphics.  Jane is an ISA Certified Arborist and an ISA Qualified Tree Risk Assessor.

View Jane's curriculum vitae.

You can reach her on LinkedIn or at


Ruth Pineo is the HortScience, Inc. office manager and bookkeeper.  She handles all accounts payable, receivables, insurance certificates, and contract management.  Her organizational, administration, and communication skills have been honed through work experience as a substitute teacher and bookkeeper for two small businesses.  Ruth has a B.S. in Health Science, with a minor in Marketing from California State University East Bay.


You can reach Ruth at






Professional, experienced, honest, and friendly: the HortScience team works together for the right solution.

Bartlett Tree Experts

HortScience is now a division of Bartlett Tree Experts. We are supported by the Bartlett Tree Research Laboratories and its team of scientists and technicians, which is a significant resource that enables us to enhance our consulting services. Bartlett is also a world-class tree care company that has been in business for over one hundred years. HortScience | Bartlett Consulting will operate independently, but if you have need of tree care, local Bartlett offices are available to provide a full range of tree care services, including pruning and pest management.

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