Shh! Shamrock is a sham! DUBLIN, IrelandFor one week a year, nursery owner Cecil Geddis is knee-deep in shamrock, the delicate three-leafed plant that people the world over associate with Ireland and St. Patrick's Day. "You have to move fast in this business. Nobody wants to buy a shamrock on March 18," said Geddis, whose nursery has produced 80,000 shamrock plants, most shipped out in cartons bearing leprechaun decorations and labeled: "Authentic shamrock -- grown in Ireland."While wearing a freshly cut shamrock is a fading tradition in Ireland, a few savvy growers and seed merchants are wooing foreign buyers and...