In Roman times, Wheat was thrown at the bride and groom as a symbol of fertility. Under Queen Elizabeth I, wheat cakes where broken up and thrown instead. Once they became costly, rice was a cheap substitute, and it "stuck"
The Urban Legend that raw rice causes birds to explode has been found to be false.Because of this rumor, bird seed or bubbles are now being thrown at weddings.
It is an Italian Tradition to throw Confetti at weddings. The confetti symbolize money and good fortune for the couple.
A Scottish tradition is to throw flower pedals on the couple. This is also a symbol of fertility.