Tulsi also known as Holy basil and Vrinda, is a sacred plant in Hindu belief. She is regarded as the avatar of Goddess Lakshmi, and thus the consort of the Lord Vishnu. The offering of its leaves is mandatory in ritualistic worship of Lord Vishnu and his avatars like Krishna and Vithoba.
The leaves of Tulsi that are offered to all Gods and Goddess but except Lord Ganesha, and Lord Shiva. According to Shiva Purana offering Tulsi on a Shiva linga is strictly forbidden and the water offered to Lord Shiva must never flow into a Tulsi plant. There is a puranic story behind it.
Story of Lord Ganesha
Tulsi was once a girl who was a devotee of Lord Vishnu. While she was dedicated to the worship of Lord Vishnu, once she came across Lord Ganesha who was meditating in a beautiful garden surrounded by fragrant trees. Lord Ganesha was resplendent wearing a yellow garment and sandal paste smeared all over the body. Tulsi was highly enamoured by Lord Ganesha’s pleasing look and requested him to marry her.
Lord Ganesha said he was living the life of a Brahmacharya and an ascetic. So he cannot even think of marriage since it would hinder his austere life. Tulsi was annoyed listening to this and therefore in utter disappointment, she cursed him that he will undergo a forceful marriage even against his will. Though Lord Ganesha is a highly benevolent one, the rude behaviour of Tulsi evoked his anger. Therefore, he cursed her that she will face a misfortune under which she shall be condemned to marry a demon and suffer under him. Tulsi realized her mistake and now prayed Lord Ganesha to save her from the curse.
Lord Ganesha was now pleased and pardoned her. He said as per the curse she shall marry a demon and after one life, she shall become a plant in her next birth. Thereon she shall be heralded by all for her exceptional medicinal properties and shall become very dear to Lord Vishnu but will not be offered to him.
Story of Lord Shiva
In time, Tulsi gave up all her royal comfort and went to Badrinath to perform penance to gain Lord Vishnu as her husband. The god Brahma was pleased with her penance but told her that she would have to marry the demon Shankhachuda before she could marry Lord Vishnu. Sudama, a part-incarnation of Lord Krishna was born on earth as the demon (Shankhachuda) due to a curse. Shankhachuda, who also pleased Brahma with his penance, was granted the Vishnu-Kavacha (armour of Vishnu). Also blessed that as long as his wife’s chastity was retained and Vishnu-Kavacha was on his body, no one could slay him. Shankhachuda and Tulsi were soon married.
But he was filled with pride and terrorized the beings of the universe. To rescue the universe, Lord Shiva challenged Shankhachuda to war, while Lord Vishnu went to Tulsi to break her chastity. Vishnu assumed the form of Shankhachuda and compelled Tulsi to have coitus. With her chastity broken, Shankhachuda was killed and Sudama was freed of his curse. In middle of their lovemaking, Tulsi recognized the impersonator. Lord Vishnu appeared in his true form. And urged Tulsi to abandon her earthly body and return to his celestial abode as Lakshmi, his wife. Tulsi’s mortal remains decayed and became the Gandaki River, while her hair transformed into the sacred Tulsi plant.
The legend ends with Vrinda cursing Lord Vishnu to become a stone. Turning him the Shaligram stone (which are found only in the Kali Gandaki River of Nepal) and God Vishnu transforming Vrinda into the Tulsi plant. She gain the status of a goddess named Tulsi, while his earthly form is the Tulsi plant. As Vrinda’s demon husband Jalandhar was killed by Lord Shiva, so she refused to worship him.
This is why Holy Basil or Tulsi leaves are not offered to Lord Shiva and Lord Ganesha. Whereas the puja offer to Lord Vishnu is incomplete without an offering of leaves.