With the advancement of medical technology and the implementation of National Health Insurance, the Taiwanese have access to reliable and relatively inexpensive medical care. This has caused an increasing life expectancy. The elderly population aged 65 and over in Taiwan has increased from 9.02% in 2002 to 11.15% in 2012, which represents an increase of 2.13% over the past 10 years. Taiwan is therefore one of the world's fastest aging countries. While the physical condition of the older people declined, they are unable to keep independently. The institutional care has therefore become an available option. However, senior long-term care centers usually focus mainly on the physical care needed by the elderly to perform daily activities and seldom focus on their mental needs. Based on the above facts, this research was held in two institutes, namely Taoyuan Veterans Home and Chubei senior care center, two different types of elderly care center residents participate in 8 weeks horticultural therapy program. The research results indicated that during horticultural therapy, 87.9% of participants whose mental status improves or remains stable. It is also revealed that horticultural therapy is best for improving cognitive and physical wellbeing in institutions for people with dementia and for people with disabilities. Therefore, this research can be used as a reference for senior long-term care centers that implement horticultural therapy.