Jivas are deprived of the service of Sri Krishna, when they unfortunately become averse to Him due to misuse of relative independence. It is narrated in 'Brahma Vaivarta Purana' that 'Vrinda Devi' appeared in this world as 'Tulsi' accepting King Dharamadhwaj and Madhavi Devi as her parents in Kartika Purnima Tithi as per desire of Sri Krishna and Srimati Radha Rani. As there was none equal to her in beauty, she was named 'Tulsi'. Tulsi made a lila in performing severe penance to get 'Narayana' as her husband (Pati) and got the boon of Sri Brahma in regard to this. As per desire of Srimati Radha Rani, Sudama Gop appeared in this world as 'Sankhachur Danava', with whom Tulsi at first was married. Sankhachur Danava seized 'Swarga' (abode of demigods) by his tremendous power. 'Devatas' (demigods) at first took shelter to Brahma, then Siva and ultimately Vishnu for their rescue from the oppression of 'Sankhachur Danava'. Vishnu Bhagwan appeared, killed Sankhachur Danava and fulfilled the desire of Tulsi. Vishnu conferred boon on Tulsi that her body would be Gandaki Nadi (Gandaki River) and her hairs would be Tulsi. Vishnu Bhagwan appeared in this world as Salagram Sila.
Whatever is done by the Will of God is for the eternal benefit of all, as He is All-Good. Cow-dung (stool of cows), Conch-shell (bone of an animal) have become sacred by the Will of Lord. So what difficulty is there in believing 'Tulsi' as the Holy tree appearing in this world by the Will of Supreme Lord Sri Krishna to bestow on us His service? There is nothing impossible for God Who is Omnipotent. God can appear in this world in any form He likes, for the eternal good of the enslaved Jivas, over whom He has got affection. You are to perform Tulsi puja daily.
The glory of Tulsi has been narrated immensely in all scriptures. It has been stated in the scriptures that only most fortunate persons have got the opportunity of being cremated by Tulsi tree after death. Even if a bough or branch or twig of Tulsi tree is offered on the dead body during cremation, the person will get emancipation from all sins. But Tulsi branch should be put on the upper portion of the dead body.
--- His Divine Grace Srila Bhakti Ballabh Tirtha Goswami Maharaj