Nelda Matheny is senior consultant at HortScience | Bartlett Consulting, divisions of the F.A. Bartlett Tree Expert Company. She specializes in tree evaluation and management, problem diagnosis and landscape plant selection and suitability assessment. She has particular experience in managing sites irrigated with recycled and low quality water, landscape soil assessment and management, and plant evaluation and management.

For over 35 years, Nelda has been providing consultation for landscape architects, contractors, owners, developers and public agencies to create enduring landscapes. She is committed to providing advice and services to promote healthy, sustainable and attractive landscapes. She helps clients select plants that are well suited to the site and manage them to enhance and protect environmental quality and conserve natural resources

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


Darya Barar manages the HortScience | Bartlett Consulting (H|BC) office of 11 employees, nine of whom are Certified Arborists with six are Registered Consulting Arborists. During her tenure with H|BC Darya worked with the City of Menlo Park on their Heritage Tree Ordinance update, the City of Vallejo on a street tree ordinance update and is an on-call Arborist for the City of Berkeley. Darya specializes in urban forestry management with 14 years of experience in the municipal setting. She has particular experience in disaster management. Darya has extensive experience working with community groups, state and local agencies on tree ordinances, master plans and large scale tree replacement projects.

Darya is a Certified Arborist (WE-6757A).  View Darya's curriculum vitae.  You can reach her on LinkedIn or at




Pam is a Certified Arborist with a background in landscape architecture. As an arborist, she has surveyed and performed tree assessments for public and private landholders throughout the Bay Area. She has recently advised the Climate Action Now! (CAN!) organization in San Francisco on tree selection for the Sunset Boulevard Reforestation Project, which involves SFPUC and SFDPW, funded through California ReLeaf.

Her landscape career has included work on resort planning projects in the U.S. and Canada, campus master planning, and landscapes for schools, commercial and residential projects throughout California. Pam has extensive experience in project management and team coordination, and has provided landscape design and construction management for housing, streetscapes, trails and playgrounds as well as SFUSD Green Schoolyards.

Having recently joined the HSBC consulting team, Pam is already immersed in tree inventories, construction monitoring, and report preparation for housing, schools, commercial redevelopment, and residential projects spanning most of the compass points and micro-climates of the greater Bay Area.

Pam is an ISA Certified Arborist (WE-9617A), ISA Tree Risk Assessment Qualified, and a Registered CA Landscape Architect (LA 5039). She also has a University of California, Berkeley Extension, Landscape Architecture Certificate a Bachelor of Fine Arts from New York University, Tisch School of the Arts.

View Pam's curriculum vitae.


Jane Whitcomb joined HortScience | Bartlett Consulting in 1995. She specializes tree assessment as well as mapping systems. Jane is familiar andexperienced in a variety of landscapes in the Bay Area from oak woodlands to planted landscapes.

View Jane's curriculum vitae.

You can reach her on LinkedIn or at


Amanda Paulos is the HortScience Bartlett Consulting administrative assistant. She handles all accounts payables, receivables, insurance certificates, and contract management. Her organizational and accounting skills have been honed through work experience as an AP/AR clerk for a small business and a personal banker for a major bank. Amanda has a certificate in accounting from Portland Community College.

You can reach Amanda 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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