Rebecca Haller, HTM, directs the Horticultural Therapy Institute in Denver, Colorado, is affiliate faculty for Colorado State University, writes curricula, and teaches horticultural therapy classes at sites across the U.S. She wrote for and co-edited two major textbooks: Horticultural Therapy Methods: Connecting People and Plants in Health Care, Human Services, and Therapeutic Programs and The Profession and Practice of Horticultural Therapy – both used extensively in the US and around the world. In HT practice, she developed a vocational HT program in 1981 (still in operation) for adults with developmental disabilities and provided HT and TH for a wide array of people through Denver Botanic Gardens. 

She has served as president and board member of AHTA and is active on work teams with a particular interest in education and professional development. Research has focused primarily on issues and data concerning education in the field of horticultural therapy as well as professional issues. She is passionate about the healing and therapeutic benefits of gardens and gardening.

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Nature Rx: Prescribing nature to promote human and planetary health

Dr. Robert Zarr, MD, MPH is a physician researcher and public health pediatrician based at Unity Health Care, Inc and Children's Hospital of Eastern Ontario. He is the Founder & Medical Director of Park Rx America, a non-profit organization whose mission is to decrease the burden of chronic disease, increase health and happiness, and foster environmental stewardship, by virtue of prescribing Nature during the routine delivery of healthcare by a diverse group of health care professionals.

Dr. Zarr has provided medical attention to BIPOC and immigrant populations for more than 20 years. Robert is also a certified nature and forest therapy guide. You will often find him walking or hiking on nearby trails and spending time near his neighborhood trees.