Rice is considered to be a “life giving” seed. It is thought that by throwing it on the couple they will be bestowed with fertility and have many children. According to http://www.ehow.com The tradition of throwing rice goes back centuries. Ancient Romans would shower a newly married couple with wheat, which symbolized fertility.
By the Middle Ages, wheat had been replaced with rice, which was also considered to be a symbol of fruitfulness. Showering a new couple with rice was believed to help them have children. In these times, the act of throwing rice was also believed to help keep evil spirits away from the bride and groom. Due to the issue that some say the rice that is thrown can be harmful to birds (not to mention it can also get slippery), new alternatives have emerged such as blowing bubbles, waving wands of ribbons, and even throwing bird seeds just to keep in the tradition of throwing something.
During Rev. Pam’s ceremonies, she has replaced this tradition with bubbles symbolizing prayers and positive energy for the couple floating up to the heavens.Though it is not certain exactly when or where this rice throwing custom originated from, it is thought to have stemmed from an ancient pagan tradition.