Buddha Day (Hanamatsuri “flower festival” in Japanese) is commemorated on to celebrate the birth of Siddhartha Gautama, who later became enlightened as Sakyamuni Buddha. [wiki ]
All religions are tinged to some degree by mythology and mysticism. The traditional stories of Queen Maya’s dream of the white elephant entering her body and events surrounding the birth of Prince Siddhartha certainly fall into the category of mythology.
The various rites observed during Buddha Day service are based upon events at the time of Prince Siddhartha’s birth. The hanamido (see picture), a miniature floral altar of bright flowers, provides the setting of the beautiful Lumbini Garden. The statue of the baby Buddha, with his arm extended, illustrates the merits of Amida Buddha, reaching out to all beings. The pouring of sweet tea on the statue of baby Buddha (kambutsu) represents the gentle rain which fell on Lumbini Garden that day.
Hanamatsuri, or “Flower Festival,” is held to commemorate the birth of Siddartha Gautama in Lumbini Garden. He was the manifestation of Amida, the Buddha of Infinite Higher Wisdom and Compassion. During the service, a flower shrine known as hanamido, is set up in front of the main altar as a symbol of Lumbini Garden. In this shrine is placed a statuette of the infant Buddha, pointing his right hand toward the heavens and his left hand towards the earth. The sangha offers flowers and pours sweet tea over the image. Kambutsu is the rite of “bathing the body of the Buddha.” This simplified reenactment of the Buddha’s birth signifies glory and joy that filled the world at this event.
– From Jodo Shinshu, A Guide