Kindly refer Mattapaliyil malarnda Paramporul a tamil book by Lakshmi Narasimhachar in which it has been mentioned in srivaikundam a tulsi plant is found next to 10 other plants.Lord Narasimha telling to Thayar Rajyalakshmi in mattapali [in Andhra] how there will be tulsi plants in srivaikundam and how the fragrance come from that. If Krishna is offered a tulsi leaf he is the most satisfied. Based on this our ancestors planted tulsi plant in the house on the maadams by lighting a lamp in the evening and putting a kolam in the morning. Like Lord shiva is fond of Bilva leaf Lord Vishnu is fond of Tulsi leaf. Tulsi leaf should not be plucked in a hard manner. It should be softly plucked that too after bath in the mornings within 8 am only. Tulsi gayatri is TULASI PATRAYE VITMAHE MAHA LAKSHMAICHA DEEMAHE THANNO TULASI PRACHODAYAATH.