In the scriptures, Dev Uthani Ekadashi is considered to be a very prominent Ekadashi. Ekadashi of Shukla Paksha of Kartik month is known as Dev Uthani Ekadashi, Devotthan Ekadashi and Prabodhini Ekadashi. On this day, Lord Vishnu wakes up from four months of sleep. From this day itself, Manglik works also start. This time Dev Uthani Ekadashi is on Sunday, 14th November. On this day, the Shaligram form of Lord Vishnu is also married to Tulsi. Tulsi is very dear to Narayan. It is a religious practice that Narayana first listens to Tulsi's voice after waking up from sleep. Because of this, people also worship Tulsi on this day and ask for wishes. Here's why Tulsi got married to Shaligram.
Here's the story:-
According to the legend of Shivpurana, Mahadeva's anger was headed to an eminent demon, who was later called Daityaraj Jalandhar. Jalandhar was married to Brinda. Brinda was a husbandly woman. Jalandhar was blessed that he could not die unless his wife's chastity was destroyed. Jalandhar had created a hue and cry all around. He had conquered heaven with his might and was badly crushed by the arrogance of his power. One day he reached Mount Kailash. There he tried to kill Mahadev. Being a part of Mahadev, he was as strong as Mahadev, as well as the power of Brinda's chastity. Because of this, even Mahadev could not kill him. Then all the gods begged Narayan. Then, Narayan, dressed as Jalandhar, approached Brinda. Brinda considered him her husband and started behaving like a husband. This broke her chastity and as soon as she did so, Brinda's husband Jalandhar was defeated and killed in the war.
Brinda got angry when she came to know of Narayan's Leela and cursed Narayan for being stoned. Then, Narayan became a stone. As God became a stone, there was an imbalance in the world. After that, all the deities approached Brinda and begged her to free Narayan from the curse. Brinda then freed them from the curse and self-immolation. Where Brinda was demolished, the tulsi plant grew. Then Narayan said, "Brinda, you have become dearer to me than Lakshmi because of your chastity. To realize your curse, one of my forms will remain on earth like a stone, known as Shaligram. You will always be with me in this form of mine. I will not accept the prasad without Tulsiji.'' From then on, Tulsi was worshipped as a divine plant and on the day of Devotthan Ekadashi, a tradition of tulsi marrying Shaligram started.