Tulsī is a sacred plant. It has been mentioned in Skandpurān that some of the drops of nectar fell on the earth during the process of Samudramanthan (churning of ocean). Tulsi was formed out of them. It was handed over to Shrīvishnu by Deity Bramhā. Tulsi is liked by Shrivishnu and hence it is specially offered to Shrivishnu. While citing the importance of tulsi it has been mentioned in Padmapurān that offering flowers made of gold, stones and pearls do not have even one sixteenth of the importance of tulsi! Sins of even many eras are destroyed by sight, touch, meditation, obeisance, planting and use of tulsi. All Deities reside in the plant of tulsi from its roots to the tip. It constantly emits the principles of Deities and purifies the surrounding atmosphere. It is even said that whoever has a garden of tulsi in the front yard of his house makes the surrounding nine miles area (yojan) as pure as river Ganga. Click here to understand this further.