Saint Patrick used the shamrock to explain the Holy trinity to the Irish. It took so long to get through that his Ash wood walking stick had taken root by the time he was ready to move on.
https://en.wikipedia.org/wiki/Saint_Patrick#Legends
Se more details at https://www.flickr.com/photos/144027177@N05/albums/72157676600940748/with/45372666475/
