Legend of Lord Ganesha and Tulsi is mentioned in many Indian Puranas, such as Brahmavaivarta Purana, Ganesha Purana, Linga Purana, Mudgala Purana, Varaha Purana and Shiva Purana. Lord Ganesha, popularly known as Ekadanta, is the son of Goddess Uma (Parvati) and Lord Shiva. He is the brother of Lord Kartikeya. The legends of the Hindu god describe his nature and character. This tale is related to Tulsi, which is an herb that belongs to the basil family. Lord Ganesha is worshipped with various flowers, fruits and sweets but the leaves of Tulsi are not used in His veneration.
The legend states that once Lord Ganesha was involved in intense meditation on Lord Vishnu on the banks of River Ganges. He wore yellow robes and was adorned with precious jewellery. The body of the deity was smeared with ointments and aromatic sandal paste. When Tulsi saw Ganesha meditating in this magnificent form, the beautiful maiden fell in love with the elephant headed deity. She requested Him to marry her. Tulsi was the daughter of Dharmatmaja and did deep meditation to gain an appropriate husband. But Ganesha humbly rejected her request as He was an eternal bachelor and vowed to remain celibate.
The rejection from Lord Ganesha infuriated Tulsi and she felt severely insulted. She immediately cursed Him that the deity will be married against His wishes and will be compelled to break His vow of celibacy.
In retribution, Ganesha cursed her that Tulsi would be married to a demon and later the sages will curse and she would become a plant. Then Tulsi became apologetic and prayed and praised the lord. Ganesha was appeased and He announced that she will be considered as the most sacred and supreme plant. All the gods, deities and sages would adore her, especially Lord Krishna. All the devotees would worship the gods with the leaves of Tulsi in order to attain liberation in Swarga Loka or heaven. But the sacred leaves of the plant would never be used in His as she is unacceptable to him. Then Ganesha began his deep mediation.
Later Tulsi engaged in intense meditation at the holy lake of Pushkara. She eventually became the wife of Shankhachuda, the demon king. Tulsi transformed into the sacred basil plant after the death of her husband.