A giant shamrock waves to spectators during the annual St. Patrick's Day parade in Montreal, Sunday, March 16, 2014. (AP Photo/The Canadian Press, Graham Hughes)
We all know what a shamrock looks like, but—speaking in scientific terms—just what is it? A clover? A wood sorrel? Some other type of plant? Unfortunately, there's no single answer: The shamrock is the stuff of legend, not science, the Smithsonian reports.