Why Do we worship Tulsi ?

Significance of Tulsi Pooja: For Hindus, Tulsi is considered the most sacred plant. In fact it is known to be the only thing used in worship, which, once used, can be washed and reused in Puja, as tulsi is regarded self –purifying. All offering are considered incomplete without the inclusion of the tulsi leaf-hence, we use it in worship. 
Tulsi also symbolizes Goddess Lakshmi, the consort of shri Vishnu. Women worship the tulsi plant for happy married life. 
The tulsi leaf has great medicinal value and is used to cure various ailment, including the common cold. 
We should offer water to the tulsi everyday and do either one or four parikrama of the plant. This removes the evil effects of the sins
Tulsi mantra while doing Parikrama
“Yanikanicha papani brahma hatya adikanicha
Tatsarvam vilayam yati tulsi tvat pradakshinath”

Tulsi Pranam mantra
“Mahaprasad janani sarvasowbhagya vardhini
Adhivyadhi haree nityam tulsi tvam namosthute”

Tulsi mantra while plucking the leaves
“Krishnaya Vasudevaya Devaki Nandanayacha
Nandgop kumaraya Govindaya namonamah