Tulasi is annually married to Lord Vishnu. during the month of Karttika.This ritual, called the 'Tulasi Vivaha' inaugurates the yearly marriage times of year in India.
On this day Goddess Lakshmi in the form of tulsi and Shrivishnu in the form of Shrikrushna are worshipped. To welcome them and to imbibe the maximum benefit from their frequencies, a marriage ritual is performed in the evening. Since Shrikrushna is the actual energy of action of Shrivishnu, the frequencies of Shrikrushna get activated on these days. These frequencies are related to the absolute water and absolute fire principles so on these days one sees the spread of the light of hope in the evenings, feels enthusiastic and experiences a coolness on the skin. On the day of tulsi Vivah, the auspicious time of the marriage is given. During this given time only, the force of activation of Shrivishnu and Goddess Lakshmi principle increase and they merge with each other. So to get the maximum benefit from the spiritually pure component in the atmosphere it is recommended to perform the marriage during this given time.