when do children start using three syllable words

We’ve been baffled by the vocabulary she has and lack thereof. I think I expected a toddler to start saying easy short words. Colors, action words like more or up/ down…. since Christmas she has said things like "Merry Christmas", "hamburger", "basketball" and today she has been saying "bicycle"! I found another post on the subject: http://community.babycenter.com/talk/a5407815