As adolescence (12~18 years of age) is in the stage not fully developed both physically and mentally, probation education is usually adopted to reclaim the juvenile delinquent. Under detention, the juvenile offenders being isolated in a controlled place are subjected to physical and mental stresses. Horticultural therapy is a supervised activity using plants and plant materials, to improve people’s well-being based on our nature-loving and intimate relationship with plants. Whether horticultural therapy program can be incorporated into the probation education curriculum at a juvenile detention house and whether the juvenile delinquents can be benefited to these programs and to what extent? How much these juveniles accept the courses and learn something or what kind of horticultural programs they would prefer? This study is conducted through an action research model to provide these answers and to serve as a reference for future improvement and implementation of horticultural programs in a juvenile correction center. Both qualitative and quantitative analyses are given to collected data from questionnaire, observations and clients’ report. The horticultural activity programs including “basic horticultural technology” and “utilization of gardening materials” are conducted bi-weekly for one and half hour period of time. Each session is designed to be complete in itself or the most after two classes so that the work can be shown within the session. The results show that horticultural activity, different from other classroom programs, offers hand-on experience and helps to stimulate learning. The activity can relieve the juvenile offenders and let forget the status of being under detention temporarily. They would obtain a variety of positive emotional experiences as they get achievements and build self-esteem in successful activity. From the horticultural programs, the juvenile participants obtain plant knowledge and gardening skills, developing creativity and environmental awareness. In a team project they can practice the patience, friendliness, cooperation and carefulness. The program also inspires the clients to actively think of their future career choices and leisure activities. The seasonal project linked to a festival enriches the program with variety and fun, meeting different individuals’ needs and serving flexibility to any client with indefinite length of stay in the program. Each session comprises lecture lesson and hand-on activities to strengthen the students’ learning. Various stimulating techniques are employed for the lecture part to enhance the students’ involvement like giving the session an interesting name, using multimedia and Q & A form. Assigning 2 to 4 clients in an activity group can increase their participation and reduce isolation. The juvenile offenders generally find the horticultural activities fun and interesting. The therapeutic horticultural program in a detention house can provide the juvenile offenders physical, psychological, educational and social benefits, leading them to positive emotion and behavior.