Uttarakhand (India) is considered the abode of gods or Devbhumi. Mahasu is one of the superintending deities of the Jaunsar-Bawar area of Uttarakhand. In the Jaunsar-Bawar, Mahasu is considered not only the deity but also worshiped as the administrative lord. As per the folklores, it is believed that the deity came from Kashmir, India, centuries ago. This study is aimed to document the plants and plant parts used in the different rituals of the Mahasu deity. Another objective of the study is to find a connection between the history of the botanical expansion of the Nargis plant and the migration theory of the Mahasu brothers. There are 20 plant species that are used in the different rituals of the deity. Narcissus tazetta is considered one of the sacred species among the community. The botanical history of the expansion of Narcissus tazetta in the Indian Himalaya and Uttarakhand supports the claim of the community that the deity Mahasu arrived in the Jaunsar-Bawar area from the Kashmir region of India. People use mostly local plant products in the different rituals of the deity. The study interconnects and supports the narratives of the folklores with the botanical information. Thus, provide a novel approach to understanding folk knowledge pertaining to the migration of a deity or community by tracing the migration of plant and animal species mentioned in the legends.