Importance or significance of Tulasi Vivaha or Tulsi Saligram Vivaha is mentioned in Puranas and many Holy Scriptures.
Lord Brahma observed Tulasi Vivaha puja in Pancharatra Agama procedure (5-day puja Agama siddhantha procedure) as per Vasista’s ‘Hari Bhakti Vilasam’ scripture. The puja should be done at Homa gunda by Vedic pundits. Mantras are recited from Shatha kumbha suktam, Shanti sankalpam, Pavamani suktam, Nava suktam, Jeeva suktam, and Vaishnava samhita.
After Homa Purnahuthi, abhishekam to Lord Vishnu and Tulasi Mata are performed. Those who donate cow to poor farmers and Brahmins will be blessed with wealth and prosperity. A Holy Scripture called ‘Vishnuyamala Tantra’ also explains the significance of Tulasi Kalyanam.
‘Bruhath Stotra Ratnakaram’ explains the Tulasi Vivaha puja as – those who observe Tulasi Puja will get rid of all sins he/she committed in this life. And those who watch and hear Tulasi kalyanam puja will also get the equal result of performing the vrata.
Tulasi Vivaha is performed on Uthwana Ekadashi / Ksheerabdi Dwadashi / or Kartik Purnima day. Here you can read Tulasi Vivah Vrat katha or the story associated with Tulasi Vivaha.