This study aims to understand the theoretical basis (ecopsychology) and operational steps of horticultural therapy and to understand how horticultural activities can exert physiological and psychological effects on elderly persons with dementia. The accumulated actual benefits of horticultural therapy are widely respected by the medical system. Furthermore, through the introduction of horticultural therapy in Taiwan and abroad, readers will better understand the status and development of horticultural therapy in Taiwan and the certification of horticultural therapists. By reviewing the literature and related case studies, the application and treatment benefits of horticultural therapy are discussed. With a broader perspective, the conclusion of this paper is that horticultural therapists and professionals in various other fields should be more creative, combine their own advantages, accumulate practical experiences, and promote this ＂green care＂ at all levels and platforms and continue to help people find health with the power of plants and nature.