An accomplished ecologist with 20+ years in the environment sector and over a decade of experience in leading for purpose organisations, Cassandra brings deep expertise in executive leadership, strategic planning, financial management, cross-sectorial partnerships and stakeholder engagement. She has a passion for driving behaviour change and promoting environmental stewardship and is excited to be uniting the collective voice of those dedicated to protecting plants – our planet’s life support system.
Board Members
Katherine Zhang
Director, Chair of Finance and Risk Committee
With extensive skills in strategic planning, operations improvement, financial risk management and ITC System Transformation, Katherine is passionate about the growth of BGANZ and securing its long-term financial sustainability. Katherine holds a Master of Accounting and Finance, Bachelor of Finance and is a Chartered Accountant.
Leonie has 25+ years’ experience in botanic garden management, public realm development, community engagement, visitor programming, master planning, and infrastructure delivery. She holds a doctorate in taxonomy and palaeobotany, plus business administration and company director qualifications. She is the Deputy Director of Collections at the Botanic Gardens and State Herbarium of SA and a member of the BGANZ Finance and Risk Committee
A career spanning over 30 years in botanic gardens, Wolfgang is currently Director of the Christchurch Botanic Gardens and Garden Parks. He is a trustee of the NZ Gardens Trust and the Horticultural Ambassador for Grow Ōtautahi, Christchurch Garden Festival and a member of the BGANZ Member Committee.
Wolfgang has supported research for the World List of Threatened Trees before becoming Assistant Curator at Ness Botanic Gardens. He then became Curator of the National Botanic Gardens of Wales, later serving as Curator and Director at Sir Harold Hillier Gardens. He was trustee of Plantnet, UK and Ireland for 10 years.
John Siemon
Director
John is a Horticultural Scientist and the Director of Horticulture & Living Collections at Botanic Gardens of Sydney. John’s expertise includes plant physiology, plant breeding, tissue culture and germplasm conservation. As a leading expert in his field, John is committed to advancing the science of horticulture, preserving plant diversity and sharing his knowledge with others.
With nearly 30 years dedicated to Australian flora conservation, Michael has led major regional botanic gardens, securing substantial funding, fostering strategic partnerships, and developing successful volunteer programs. Currently managing Eurobodalla Regional Botanic Garden, he has held leadership roles in BGANZ, Aus Plant Society and a 3,000-hectare nature reserve.
In 2023 Michael won a National Garden Clubs of Australia Award for services to the community.
Emily Drewniak is a philanthropy and governance specialist with more than 20 years’ experience growing support for conservation, education and the arts. She has held senior roles at the Botanic Gardens and State Herbarium of South Australia, Country Arts SA, and now serves as Philanthropy Executive (South Australia) at Bush Heritage Australia. Across these roles she has led major campaigns, built donor circles and crafted partnerships that connect people, plants and place. Emily brings a strong focus on strategy, stakeholder engagement and a culture of giving, with particular expertise in major gifts, and fundraising governance. She also serves as a Board Director with MusicSA, supporting the growth of contemporary music in South Australia. On the BGANZ Board, Emily is committed to strengthening financial sustainability across the botanic gardens sector and championing the vital role of gardens in biodiversity conservation and community
The Member Committee connects the broader membership with the Board, providing insights on sector challenges, trends, and growth opportunities. Consisting of members, it ensures BGANZ remains responsive, relevant, and aligned with its purpose.
Finance and Risk Committee (FRC)
The FRC advises the Board on financial and risk management, supporting oversight of financial affairs, strengthening risk and control frameworks, and ensuring compliance with legal and regulatory obligations. The committee is comprised of Board members with relevant expertise.
Marketing and Fundraising Committee (MFC)
The MFC supports the Board in fulfilling its responsibilities relating to revenue generation, public profile, member value, and stakeholder engagement. The committee provides strategic advice, guidance, and oversight in relation to marketing, communications, partnerships, and fundraising activities.
