Board of Directors

Ruth Bancroft


Ruth Petersson was born in 1908 and was raised in Berkeley. Ruth developed an appreciation for plants at a very early age. Ruth began gardening right away, and planted a large garden around the main house in 1950. Her interest in different plant groups evolved over time to include bearded irises, roses, herbs, alpine plants, perennials, and more. In the 1950s, Ruth purchased her first succulent, a single potted aeonium. She quickly became fascinated with water-conserving plants and began collecting them. She amassed a huge collection of potted succulents, which were grown in lath-houses and greenhouses around her house. In 1971, the last walnut orchard on the property was cut down, and Philip offered Ruth the three acres to begin a new garden using her large collection of succulents, which had outgrown their space. Ruth, then in her 60s, seized this opportunity. She enlisted Lester Hawkins, co-owner of Western Hills Nursery, to design the layout of pathways and garden beds. Ruth herself chose the plants, many of which were planted out from one gallon containers. She said that if you plant a plant from a smaller pot, it will get established faster than a larger plant from a larger pot and will soon be bigger than the one from the larger pot. She said to never use a plant from a pot larger than one gallon. Many of the plants in the garden were from 3- or 4-inch pots.

Cheryl Nobusada

Board President, E.D. Performance Review Committee Chair

Cheryl has more than 20 years of finance, operational, compliance and risk management experience.  She enjoys consulting for small businesses by helping them become operationally efficient and thrives on volunteering with local non-profit organizations to support her community.  She recently joined the Cancer Support Community as their Finance and Operations Manager after being a volunteer for many years.  Previously, she was the VP of Investor Operations at LendingClub, the Director of Client Services at a San Francisco based technology hedge fund, and held various roles at Deutsche Bank working with individuals to achieve their financial goals.  She currently serves on the Hope Walk Committee for Cancer Support Community and is also a volunteer at Lamorinda Villages.  Cheryl and her husband, Ryan Kosakura, have been members of the Garden since 2015 and she has volunteered in the Nursery and various Garden events since that time and is an Audit Committee Chair.

Earl Ruby

Vice President, Finance Committee, Garden of D’Lights Committee, E.D. Performance Review Committee

Earl owned and ran a software consulting company in Walnut Creek for 9 years. He is currently a Staff Engineer at VMware, orchestrating cloud infrastructure and Kubernetes clusters for GPU-based ML/AI projects. He has led an engineering teams at Apcera, built cloud storage reference architectures for Seagate, created web-based settlement, network quality of service and fraud-detection software for the wholesale telecom industry, and built wireless telemetry networks for Schlumberger. He earned a bachelor's degree in Computer Science from Cal Poly, San Luis Obispo, with a concentration in Artificial Intelligence. He has been an extremely active volunteer for the last four years.

Helen Josephine

Secretary, Governance Committee, Gala Committee

Helen Josephine joined the Garden in 2020 before moving to Concord and now that she lives close by, she has enrolled in both online and in-person courses offered by the Garden’s educational department and completed the docent program in 2022. In 2021, she utilized the Landscape Design services of the Garden to help her select water-wise pollinator-friendly natives and succulents to replace the front lawn of her new home. As a newly minted docent, she enjoys spending time in the Garden talking with visitors and sharing information about Ruth’s vision. She was a volunteer on the 2022 Gala Committee and also volunteers on other projects in support of the educational programs of the Garden. Helen is a librarian who has worked in corporate and academic libraries for over 45 years. She retired from full-time employment In 2017, after 10 years as the Head of the Terman Engineering Library at Stanford University. She is also a certified project manager and an active member of three Toastmasters International Clubs. She received her Master’s in Library Science (MLS) from the University of California, Berkeley, and her BA in English Literature from Monmouth College in Illinois.

Michael Goldberg

Treasurer, Finance Committee

Michael joined the Board in July 2022, having been a member, customer and big fan of the Ruth Bancroft Garden since 2008. He is the Vice President of Sales Operations at Planet which provides daily satellite data that helps businesses, governments, researchers, and journalists understand the physical world and take action to improve it. Before Planet, he worked at Autodesk, Seagate, Salesforce and Nextel Communications along with several start-up companies. He has an MBA from University of California, Irvine. He and his wife have been involved in volunteering to help with the collection and transportation of humanitarian aid to and building schools for girls in Afghanistan as well as helping refugees resettle in the Bay Area.

Nina Bancroft Dickerson

Governance Committee, Board Member at-large.

Nina is Ruth Bancroft’s daughter. She is a retired social services professional and active community leader. Nina has been an active volunteer and Bancroft family advisor to the Board and contributing member at the Garden for over 20 years.

Gretchen Bartzen

Development Committee, Governance Committee, Folly Complex Renovation Committee, Gala Committee, Sculpture Show Committee

Gretchen first joined the Garden board in 2006, and became the volunteer co-executive director of the Garden with board member and long-time Garden volunteer Billie Hopper in 2012.  Together they helped grow the Garden and run a capital campaign and construction project to build the first permanent home for the Garden, the Coit Family Visitor and Education Center, completed in 2019.  Gretchen retired as Executive Director of the Garden in 2021, and was elected to the board for a third term in October 2021. Prior to her service at the Garden, Gretchen served as Director of Development and Parent Relations at The Seven Hills School in Walnut Creek from 1995 to 2012. At Seven Hills she directed two successful $5 million dollar capital campaigns for building projects in 2000-2002 and 2008-2011.  Through her tenure at Seven Hills she also steadily increased volunteer involvement, annual giving, and the school’s endowment.  Prior to her career in fundraising, Gretchen was a teacher of English and Speech for 19 years at the secondary and junior college levels.

Judith Coleman-Cohen

Development Committee, Gala Committee

Judith made her first visit to the Ruth Bancroft Garden in 2008, and was recruited to volunteer with event planning and operations while attending one of the Garden's social events. She participated in the RBG Boosters, and assisted in the annual RBG Gala planning ever year in some capacity. Her most recent focus is on Garden events and the Annual Gala. She is currently considering various Board committees, including Ad Hoc Gala, Ad Hoc Sculpture Show, and Development / Planning. Judith has a BS Degree from Purdue University, in Food Technology. While working at her first position after graduation as the Director of Product Testing & Sensory Evaluation at Best Foods, CPC International, she went on to obtain her MS at Rutgers University. She then took a position with the Clorox Company in Oakland, California, where she was their Panel Research Director, responsible for directing specific brand and product development marketing research activities. Ultimately she started her own firm, Discovery Research, where she was the Chief Executive Officer for over 22 years. Discovery Research specialized in exploratory, motivational and creative marketing research techniques, particularly focus groups and one-on-one interviews. Judith was also very active in the Acalanes School district, as Chairman of Diversity at Campolindo High School, as well as a liaison to the school district for community diversity programs. She also volunteered as the Boy's Varsity Tennis Team Coach from 1999 to 2002, and she accepted a part-time position as General Manager of the Lafayette Tennis Club in Lafayette, California, where she provided management support at a full-service sporting club. Primary efforts at the club included staff hiring and supervision, designing and implementing marketing strategies, and promoting club events. She continued to work in the field of Marketing Research until 2014, when she officially retired. Judith was on the Board of Directors of Forewomen Golf Association, San Ramon, California, in charge of Charities and Golf Clinics. She currently is serving on the Board of Directors of Boundary Oak Ladies Club, Walnut Creek, California, as Secretary. Judith's father, Daniel Coleman, was an avid gardener, and while she cannot necessarily boast of having his "green thumb," she has always loved working with plants, particularly succulents and cactus, and she considers herself a major fan of the Ruth Bancroft Garden and all it has to offer.

Gail Giffen

Finance Committee, Sculpture Show Committee

Gail is a real estate investor and past owner of two Bay Area pizza restaurants.  Gail is an art collector and has served on the annual Sculpture Show Committee since 2006 and a board member on and off since then. Gail is also active in supporting all of the Garden’s annual major fundraising events.

David Mitchell

Garden Committee, Ad hoc Folly Complex Renovation Committee Chair, Audit Committee Chair, Finance Committee,, Horticultural Advisory Committee

David Mitchell retired as a Vice President and Senior Project Manager at AECOM, San Francisco in 2019. He has over 40 years of experience in construction project management and consulting services. David served as the project manager for the Visitor and Education Center from 2013-2019, during which time he first served on the RBG board. During his career David acted as a project manager on a diverse variety of projects including transportation, power generation, medical and educational facilities, as well as various commercial projects. In addition to his role as project manager, he has provided clients with a range of consulting services focused on the effective implementation of contract administration processes, project controls, and the mitigation or resolution of contract disputes, as well as the development and implementation of specialized training programs. David has a B.S. in Business Administration with concentrations in Finance and Economic Analysis from U.C. Berkeley and is a retired registered Professional Engineer in the State of California and the Commonwealth of Pennsylvania. David has been a very generous supporting member and an active volunteer in the Garden for almost 20 years. In addition to his board responsibilities, he is currently working with the Garden staff regularly, and has completed the Garden’s docent training program.

Roger Ravenstad

Garden Committee

Roger Ravenstad currently serves as the Parks Planning & Design Manager for Fremont California and is a seasoned government leader with 36 years of experience in public and private practice designing and building park and recreation facilities, public spaces, corporate campuses, and retail throughout Northern California. Roger has steered his career toward a focus on sustainable long-term quality public places for people. He feels strongly that great places are defined by their ability to enhance peoples qualify of life, sense of community, and connection to the natural environment. During his leadership, Fremont’s parks have been ranked as one of the top park systems in the nation by Trust for Public Land. At the City of Fremont, Roger manages the $100 Million Parks Capital Improvement Program, $60 Million Parks Planning and Acquisition Program, and established the first Urban Forestry Program for the City. Roger authored the City’s Tree Preservation Ordinance and the Citywide Development Landscape Policies. Roger is a California licensed Landscape Architect, has a BS in Landscape Architecture from California Polytechnic State University, San Luis Obispo, and has a Masters in Public Administration from California State University East Bay (Hayward). Roger served in the Peace Corp Forestry Program in Nepal. For the City of San Leandro, he served on the City Planning Commission, Site Development Sub-Commission and General Plan Advisory Committee. He is a member of the American Society of Landscape Architecture, National Recreation and Parks Society, and the Pi Alpha Alpha honor society for Public Administration. In Roger’s spare time he is a lifelong skier and enjoys running, biking, and most of all, hiking in the mountains and at the beach with his partner Ken and their dog Roxie. Recently Roger has been exploring the world of succulent gardening and volunteers at the Ruth Bancroft Garden in Walnut Creek, where he lives.

Susan Ruby

Garden of D’Lights Committee, Governance Committee, Folly Complex Renovation Committee, Gala Committee, Sculpture Show Committee

Susan holds a bachelor's degree in Dietetics from Cal Poly, San Luis Obispo, and worked as a Nutritional Specialist for two years before she earned a Certificate in Engineering Drafting from Diablo Valley College, and worked as a commercial architectural drafter for 15 years.  In 2010 Susan completed a Master's in Business at John F. Kennedy University and in 2011 she also became a certified personal trainer.  Susan has volunteered at Ruth Bancroft Garden for eight years.  She has worked in the office, the Kiosk, and at special events. She has taken the Docent Program to learn more about the plants in the Garden and considers RBG one of her hobbies.

Christina Sammartino-Ascencio

Gala Committee Chair, H.R. Committee

Growing up in Alaska, Christina Ascencio has had an appreciation for nature her entire life. She now enjoys honing her green thumb in the East Bay, where she has lived for more than 10 years. For 17 years, Christina has worked as a fraud specialist for Wells Fargo Bank, an organization that supports volunteerism and encourages its employees to join local nonprofit boards. Christina knew she wanted to get more involved with the Garden after visiting for the first time in 2016 for a plant sale. Shortly thereafter, she completed RBG’s docent program to further her knowledge of drought-tolerant plants and has since volunteered at the Garden in a variety of roles. Christina has also proudly served as chair for the annual Garden Gala since 2017.

Monique Young

Development Committee, Garden Committee, Horticultural Advisory Committee, H.R. Committee

Monique who is now associated with Compass Real Estate, is a residential real estate broker in Walnut Creek, working here since 1987.  In service to the real estate community, she has been past chair and a member of the Contra Costa Association of Realtors’ Professional Standards Committee since 2000.  Professional Standards is responsible for hearing ethical complaints against Realtors from the public or other members; it also arbitrates financial disputes amongst members.  Monique has taught real estate classes at Diablo Valley College since 2000.

Mary Walker

Development Committee, Finance Committee, Governance Committee

Linda T.

Dr. Linda Tirado is a management consultant and psychologist who has studied leadership and team development for more than thirty years. She received her Ph.D. at the University of Connecticut and co-founded Strayer Tirado Consulting Group in the mid-80s, with a focus on organization and leadership development in the high tech and life science industries. Linda has been involved with hundreds of CEOs, executives, venture partners and Boards around organization, leadership, and team development. She has consulted to both public companies and nonprofits around change management, organization development, and M&A integration. Linda has had a long-term interest in education and has served on the Board of the United Way and the Board of Regents of Archbishop Mitty High School addressing issues of inclusion and diversity. She is also an enthusiastic gardener who has been a huge fan of the Ruth Bancroft Garden since her first visit during the pandemic. She is thrilled to be growing her understanding of dry gardening through the classes offered at RBG and has been delighted to share her enthusiasm with her family, particularly her four young grandchildren. She looks forward to joining the Board and staff as the organization continues to promote Ruth’s vision and evolve to address the climactic challenges of today.

Dane Callihan

Staff, Executive Director