If you think this little ditty is actually about gardening, you'd be wrong. The contrary Mary of the title is Queen Mary I, AKA Mary Tudor, who during her reign attempted to restore Catholicism as the national religion of England. She came to be known as "Bloody Mary" for apparently persecuting Protestants.

The song is believed to be a clever jab at "Bloody Mary," with the "garden growing" bit alluding to the bodies she planted in the cemetery, the "silver bells and cockle shells" referring to torture devices, and the pretty maids all in a row symbolizing people lined up for the guillotine.