Maybe the phrase originated because of pumpkin-growing contests?

Seems we have a real mystery here, folks...I searched Quinion, Bartleby, The Phrase Finder, and OneLook for some pumpkins...nada! Usually there's some citation of a known phrase. And I know I've heard it years before I encountered it in my 19th Century historical interpretation studies. Jackie's offering seems a likely source. Anyone have a clue to the origin for this one? And why no dictionary listings?