Why palms?
Palm Sunday marks the start of Holy Week, commemorating Jesus’ entry into Jerusalem. All four gospels record the crowd laying branches on the road as he rode in on a donkey. John's gospel specifically mentions palm branches.
In the ancient world, palms were a symbol of victory and triumph. They were waved for kings and military heroes. The crowd was making a political statement whether they fully realised it or not — they were greeting Jesus as a king.
So they took branches of palm trees and went out to meet him, crying out, “Hosanna! Blessed is he who comes in the name of the Lord, even the King of Israel!”
John 12:13