It may interest you to know, if you didn’t already, that the palm leaf has a long history of tradition within the Jewish religion.
Of course, we use the palms in imitation of the Jews who welcomed Jesus into Jerusalem before His passion and death, but there is a reason they did that, and it wasn’t something they just came up with on the spot.
The palm branch is used specifically in the Feast of Tabernacles. You can read about it more here:
en.wikipedia.org/wiki/Feast_of_Tabernacles
From Leviticus, Chapter 23:
As indicated in the link I provided, the Feast of Tabernacles is a remembrance of the Israelite’s time in the desert, after being freed from Egypt, and before entering the promised land. During that time, they dwelt in tents, or “tabernacles.” The palm branches are taken up to rejoice in God, who is their salvation and providence.
The tabernacles constructed during this feast have palm branches placed on top of them. They are a three-fold reminder of God’s freeing them from Egypt, providing for them in the desert, and bringing them into the abundant promised land.
When Jesus entered Jerusalem, it was not the Feast of Tabernacles, but rather the Solemnity of Unleavened Bread (the Pasch) was approaching. The Feast of Tabernacles wouldn’t be for another seven months (September/October). We should therefore take it as a sign inspired by the Holy Spirit that the Jews welcomed Jesus into Jerusalem by placing palms at His feet.
It is unlikely that they understood the import of what they were doing, but here it is: By laying the Palms at Jesus’ feet as He entered Jerusalem, they were “rejoicing before God.” They were also calling to mind the freedom that God gave them from the Egyptians, and His Divine Providence. Perhaps they truly believed that He was the Messiah, but after an earthly fashion, believing that He would free them from the Romans, as Moses had freed them from the Egyptians.
We see it now as Him freeing us from the weight of sin. So, when we take up the palms, we do so rejoicing before God for the salvation that He wrought through Jesus Christ, from our sins. This fulfills the practice done by the Jews in their Feast of Tabernacles.
One final note: we bless our palms because during the Feast of Tabernacles, Jews pray a blessing over palms every day of the feast (which is seven days).
Don’t you love how it all fits together?! I love it!