Shamrock

Can anyone explain why the three-leafed shamrock seems to have sprouted an extra leaf in much of the artwork for this year's St. Patrick's Day? The shamrock was selected by St. Patrick to help explain the Holy Trinity (Father, Son and Holy Ghost) to us heathens (although don't ask me to explain what the Holy Ghost is - I'm afraid that bit passed over our heads). Has anyone any suggestions as to what the fourth leaf might symbolise?

(Submitted with a slight shudder) https://www.youtube.com/watch?v=24963ZqW4uA

Guy

My best guess is that people have no idea about the original symbolism, and are using 4-leaf clovers because they're supposed to be lucky.

A fourth leaf for ignorance?

How many people see clover as part of their daily life? Actual clover as opposed to grass?

Almost no one.

What kind of clover do we hear about? That's right, the four leaf clover - and they hear about it out of context. What made a four leaf clover lucky was that they were so rare - so you had to search to find one of the lucky ones. But if all hear about is four leaf clover that's all you know about.