Palm Sunday is a Christian moveable feast which always falls on the Sunday before Easter Sunday. The feast commemorates an event mentioned by all four Canonical Gospels Mark 11:1-11, Matthew 21:1-11, Luke 19:28-44, and John 12:12-19: the triumphant entry of Jesus into Jerusalem in the days before his Passion.
In the …Ukrainian Orthodox Church, Ukrainian Catholic Church, and Ruthenian Catholic Church, the custom developed of using pussy willow instead of palm fronds because the latter are not readily available that far north. There is no canonical requirement as to what kind of branches must be used, so some Orthodox believers use olive branches. Whatever the kind, these branches are blessed and distributed together with candles either during the All-Night Vigil on the Eve of the Feast (Saturday night), or before the Divine Liturgy on Sunday morning. The Great Entrance of the Divine Liturgy commemorates the "Entry of the Lord into Jerusalem", and so the meaningfulness of this moment is punctuated on Palm Sunday as everyone stands holding their branches and lit candles. The faithful take these branches and candles home with them after the service, and keep them in their icon corner as an evloghia (blesing).
It is custom for people to ‘tap’ each other with their pussy willows and say:
Я не б’ю,
від нині за тиждень,
The willow is hitting,