Festival of the Entry of the Tree, for the god Attis, ancient Rome
(Origins of Palm Sunday)

Cybele and Attis
In this stage of the twelve-day Hilaria festival, the priests of the goddess Cybele would carry pine (some say palm) trees through the streets today, for the god Attis. Over time, the sacred rites of this day were appropriated by the Christians, and they were attached to Palm Sunday.
In Roman mythology, Cybele's lover and son, or grandson, Attis, betrayed the goddess, and she drove him mad. In his fallen state, Attis castrated himself and died of haemorrhage, violets springing from his blood. (Castration apparently ran in the family. Attis's mother was who was impregnated by an almond of the tree sprung from the severed genitals of Agdistis ...
A felled pine tree was covered with violets and carried to the shrine of Cybele on Mount Dindymus. It might be that one main tree was carried solemnly, and participants and bystanders waved smaller trees and branches. At the shrine, in what is obviously a Spring Equinox symbol for this life-death-rebirth deity, strikingly similar to Easter, Attis was mourned for three days until, in ritual, he was resurrected by the love of Cybele, following which the devotees engaged in joyous and unrestrained celebration ...