Significance and legend
In the Brahmanda Purana dialogue, the sage Vasishtha tells King Mandhata of the glory of the amalaki (Indian gooseberry) tree, which arose from Vishnu, and in which the Lord is believed to dwell. In the kingdom of Vaidisha, ruled by King Chitraratha, everyone observed Ekadashi. On Amalaki Ekadashi the king and his subjects gathered at a temple beneath an amalaki tree for worship and vigil. A hungry hunter, who had never practised any religious act, came by and, curious, stayed through the night listening to the stories and watching the worship, without eating.
The hunter died soon after, but by the unintended merit of that fast and vigil he was reborn as King Vasuratha. One day, while asleep in the forest, he was attacked by a band of wild tribesmen, but their weapons had no effect. A radiant goddess emerged from his body and destroyed the attackers. A divine voice told him that this was the power of Vishnu, earned through his observance of Amalaki Ekadashi in his past life.
How Amalaki Ekadashi is observed
Devotees fast and worship the amla tree, bathing its roots, applying sandal paste, tying a sacred thread around it and offering lamps, while praying to Vishnu, believed to reside in it. Parashurama is also worshipped in some traditions. In Kashi, the day is Rangbhari Ekadashi, when Lord Vishwanath is believed to bring Parvati home after their wedding and the city begins playing with colours before Holi. The fast is broken on Dwadashi after sunrise within the parana window, often with amla included in the meal.