Vanabhojanam means serving food to the devotees under holy trees, and it would be served in big temples like Tirumala, and also in small temples during the Tamil month of Karthika. The food would be served to the devotees usually under the trees like Vilva, Arasa and Vanni, and the devotees who participate in the annadanam would be blessed by the almighty. It is believed that by taking part in the Vanabhojanam event, sins committed by us by the way of killing small insects would be removed.
Vanabhojanam was organized since ancient times. Mostly it would be offered in the Vishnu Temples, and also in the Raghavendra Mutts situated at Ayanavaram, Triplicane and Perambur etc. Before offering food to the devotees, the significance of Vanabhojanam would be explained by the temple priest to the devotees, and they would also ask the devotees to put some offerings in the plate held by the priests. Sri Krishnadevaraya used to perform Vanabhojanam in the Vijayanagar temples, and during that event, his Spiritual Guru, Sri Vyasaraja Teertha used to tell holy stories about Lord Vishnu to Sri Krishnadevaraya.
Some Ancient kings instead of doing Yagnas, would perform Vanabhojanam, and they would get good results in their life, similar to doing ritual Yagnas.
For performing Vanabhojanam, we can also donate either money or in the form of provisions and puja materials to the temple authorities. It is believed that those who organise Vanabhojanam at their own cost in the temples would get great Punya (Good Karma), and they would prosper in their life.
Doing Vanabhojanam is similar to performing the great Ashwamedha Yagna, and hence let us Join in vanabhojanam, and provide our support to the performers of the Vanabhohanam.
Among all types of donations, food donation is considered as the best donation, and if we donate food during the auspicious Karthikai month, under the holy trees, we would be blessed by the divine devas in the heaven, and all of our troubles would come to an end.