Lord Vishnu enters Yoga Nidra on the Prathama Yekadashi of Ashadhamaasa (Month of Hindu Calendar that begins in July or Aug) and wakes up on the Dwadashi day of Shukla Paksha in the Karteekamaasa (Month of Hindu Calendar in October or November), which occurs four months (known as Chaaturmaasa: meaning four months) later. This Dwadashi day is celebrated as Utthan Dwadashi. Utthan in Sanskrit means ‘awakening’. Lord Vishnu once awake, teaches about life and its importance and well-being on the earth.
The greatness of Prabodhini Ekadashi was first narrated by Lord Brahma to Sage Narada and is explained in the ‘Skanda Purana’. Hence, the Yekadashi day is spent praising the glory of Lord Vishnu. Early in the morning, on the day of Dwadashi, Tulasi plant used for everyday worship in the houses is brought in and decorated with a branch of Indian gooseberry tree and a Saligrama (a sacred stone form that represents Lord Vishnu). Other decorations and embellishments like garland of flowers, Rangoli (Rangavalli) are done to this potted plant of Tulasi. Lamps are lit and celebrated with a variety of dishes, sweet and savory. This is popular as Tulasi-Damodara Vivah. The marriage is performed in the morning time with a priest or the people of the house-hold. Arati is performed to Tulasi – Damodara (Lord Krishna) in the evening and celebrated with inviting Sumangalis (married women) and offering Tamboolam consisting of betelnuts and leaves with fruits or coconut and Dakshina (coins).
A couple of legends are cited from Puranas, about the origin and importance of the Tulasi plant.
According to Puranas, Tulasi emerged before the emergence of Lord Dhanvantri during the Great Churning of Milky Ocean by Gods and demons for the Elixir (Amrita). Tulasi requested to be with Lord Vishnu forever. Lord Vishnu gave a boon to Tulasi, that no worship or offer be complete without Tulasi bud. It is therefore believed that Lord Damodara exists in this plant in the Vibhuti Rupa. Utthana Dwadashi is the symbolic wedding of Tulasi with Lord Krishna in the form of Damodara, which bestows liberation (Moksha).
According to Devi Bhagavata, Lord Krishna married Tulasi and killed a demon, who had forcefully abducted her. The marriage of Tulasi with Sri Damodara (Krishna) is symbolically performed on the Utthana Dwadashi. Krishna bestowed a special boon upon Tulasi that Sri Mahalakshmi will be eternally present in her (Tulasi). She transformed herself into a plant and Lord Krishna as Damodara entered the Saligrama, a sacred stone. Worship of Sri Damodara in the form of Saligrama, along with Tulasi, on Utthana Dwadashi is highly meritorious. Special anointment with milk and water are performed through the conch to Lord Krishna and Tulasi. After offering Naivedya with fruits and Mangalarati, the puja is completed by pronouncing the word Sri Krishnarpanamastu, pouring water into the palm and releasing it with a bud of Tulasi.