To understand the specific sign act more deeply we must look at the symbology of "trees" and especially the fig tree in biblical discourse. Trees have a consistent pattern of being used as a symbol for either individual people or collections of people/nations. (Psalm 1:3, Isaiah 6:13, Psalm 52:8, John 15:1 + many more too many to list) Very often trees with special medicinal qualities were selected to symbolize God's people in scripture. Eg: Olive Tree, Fig tree, Frankincense, Myrrh etc. (why the wise men brought the gifts they did). All the products of these trees have special medicinal/sacred properties