Significance
Holy basil (tulsi) is the symbol of spiritual purity (sattvikta). The marriage of tulsi with Shrikrushna means that 'God likes purity as a quality.' The symbol of this is Shrikrushna wearing the necklace of Vaijayanti beads.
The meaning of the word marriage is the merging and oneness of the embodied soul (jiva) and God (Shiva).
History
Tulsi Vivah is an important ritual performed in Kartik month in traditional Hindu calendar. Tulsi Vivah festival is the wedding of Tulsi plant to Lord Vishnu. Tulsi Vivah is performed by some communities on the Ekadasi day after Amavasi (new moon) in Kartik month and by some communities on the Dev Diwali day or the full moon day in Kartik Month. In 2009, the date of Tulsi Vivah pooja on Ekadasi day is October 29. The puja is also performed on the day after Ekadasi on Karthika Shuddha Dwadashi (October 30). And Tulsi Vivah on Purnima is November 2.
Tulsi Vivah is an age-old tradition and is mentioned in the Padma Purana and other ancient scriptures. Tulsi, or the Holy Basil, is the sacred plant of the Hindus and symbolizes purity and is famous for its medicinal properties.
Legend has it that a king named Jalandhar got a boon that he will remain immortal as long as his wife Vrinda is chaste (Pati Vrat). This made King Jalandhar arrogant and he declared war on other kings, demi gods and started tormenting innocent people.
Finally, the task of annihilating King Jalandhar fell on Lord Vishnu.
Lord Vishnu in the guise of Jalandhar approached Vrinda and she mistook him for her husband. They lived like husband and wife. Soon Jalandhar was killed in a battle. This made Vrinda furious and she cursed Vishnu and made him turn to Shaligram.
Lord Vishnu did not let Vrinda suffer for no fault of her. She was turned into a Tulsi plant and gave her the boon that she will find a place in all houses and she will be worshiped. Tulsi Vivah is performed to establish this divine relationship between Lord Vishnu and Vrinda.
Performing it is considered highly auspicious and good for couples. Popular belief is that performing the wedding ceremony of marrying Tulsi to Vishnu considering her as their daughter is equal to performing Kanyadan.
How to Celebrate
All around the courtyard of the house, cow dung water is sprinkled. If the tulsi plant is in a pot then the pot should be painted white. White colour attracts the Divine frequencies coming from God. Draw a sattvik rangoli around the tulsi plant and then do its ritualistic worship (puja) with spiritual emotion (bhavpurna). While worshipping, one should sit facing westward.
Prayer to be made: 'Hey Shrikrushna, Hey tulsi Devi, the energy that I imbibe from you today, let it be used for the protection of Dharma and nation. Let my warrior attitude (kshatravrutti) be activated all the time. Let me not be depressed during bad times and let my faith and devotion unto God be consistent.'
Chanting: On this day Shrikrushna's principle is activated on Earth to a greater extent. The principle is also more active around the tulsi plant. On this day one should chant Shrikrushna's name. After the puja (ritualistic worship), the surrounding becomes very sattvik (spiritually pure). One should also do Shrikrushna's chant at that time.
Uses of tulsi: Tulsi being more spiritually pure (sattvik) God's energy is attracted to it to a greater extent. Putting tulsi leaves in drinking water makes it spiritually pure (sattvik) and Energy (Shakti) is released into it. Through this water God's Energy becomes active in every part of the jiva (embodied soul).