Amalaka Ekadashi

Amalaka Ekadashi is the Vaishnava Hindu fast on the 11th day of the waxing moon in the lunar month of Phaguna.
On this occasion, the celebration is combined with the veneration of trees, a derivation of the belief that on this day, Hari (Lord Vishnu) dwells near the amalaka tree. The amalaka or Indian gooseberry tree (Phyllanthus emblica) is a tree well known for its medicinal properties. All parts of the plant, but especially its fruit, are used in Indian/Ayurvedic medicine. It has been a major source of vitamin C.

As on all ekadashi days, a fast is observed on this day, and the priests at the temples are given gifts. Worship is, however, directed toward the tree. Following ablutions in the morning hours, the priests ceremonially bathe and water the tree and then lead a puja designed for the occasion.

References
Kelly, Aidan, Peter Dresser, and Linda Ross. Religious Holidays and Calendars. Detroit, MI: Omnigraphics, 1993. Malla, Bansi Lal. Trees in Indian Art, Mythology, and Folklore. New Delhi: Aryan Books International, 2000.