To align with global trends and the swift pace of technological advancements, it is imperative to consistently update the professional standards and curriculum for horticultural therapists to meet evolving professional demands. This study used the developing a curriculum (DACUM) method to analyze the tasks and duties of Korean horticultural therapists and subsequently tailor a specialized training program for them. First, 11 experts in the horticultural therapy field participated in workshops to develop a DACUM chart that included the definitions, tasks, knowledge, skills, and attitudes of horticultural therapists. A job performance evaluation survey for horticultural therapists was also developed through these workshops. The 300 participants of the online survey were members of the Korea Horticultural Therapy and Welfare Association. The survey consisted of a 5-point Likert scale of the current performance level and future requirement level for each qualification grade. Demographic information and responses to each question were computed using a frequency analysis and percentages, grade-specific task performance evaluations comprised a one-way batch analysis of variance, and statistical significance levels were set to P < 0.05. The horticulture professional curriculum was based on competencies derived from the job analysis and online conferences with 10 professionals who participated in the DACUM workshops. The job analysis results revealed six duties with a total of 32 tasks. The results of the job performance evaluation showed that there was a great demand for the development of their convergence capabilities. Accordingly, in response to these results, new interdisciplinary convergence fields such as horticultural therapy and science (information technology), horticultural therapy, and humanities education were introduced into the specialized training. The results of this study will be valuable for improving the skills and expertise of horticulture therapists to meet social needs.