Palm leaf
(by Julie Thornock)

We just attended an institute class in which the symbolism of the palm leaf was explained.

At the time of the Savior's life, and indeed for centuries before that, a king would enter a city seated on a donkey as a symbol of peace.
That was opposed to an army entering on horses with the intent to conquer.

The palm leaf was waved as a symbol of victory.

So when the Savior entered on a donkey, he was telling the Jews that he was a king, and the waving of the palm fronds was symbolic of his victory, only not in a political sense.

This was very threatening to the Sadducees and the Pharisees, since they interpreted it as the end of life as they knew it ~ it was a threat to their livelihood.
And that's why they wanted Jesus crucified.