Trees always save the day. As you probably know by now, at the end of the story Daphne's father Peneus decides the best way to save his daughter from love-crazy Apollo is to transform her into a laurel tree. (We're not quite sure what his reasoning is on this one, but apparently it made sense to the ancient Greeks.)
Apollo feels like crap about how it all went down, so he "honors" Daphne by making the laurel his sacred tree. He also gives the tree some of his own eternal youth to make it an evergreen. So, even though Daphne is the one who turns into the tree, the laurel ends up being a symbol of Apollo himself. The god is often depicted in art as wearing a wreath of laurel, and his lyre and bow are usually decorated with laurel leaves. (Don't believe us? Check out some pictures here.)
Because the laurel was considered sacred to Apollo, wreaths of its leaves were used to decorate the winners of the Pythian Games, which were held in honor of Apollo at Delphi. It was kind of like being awarded a gold medal. Using laurel wreaths as badges of honor spread from there to the Olympic Games, and the practice was eventually picked up by the Romans. You've probably seen a picture of some random Roman or Italian dude with leaves wrapped around his head, right? (Don't know what we're talking about? Check out the great poets Dante and Ovid.) Well, those are probably laurel leaves; they were used to honor someone after a victory or great accomplishment of some kind.
(Actually, we made that sound a lot simpler than it really is. The Romans were rather obsessed with wreaths of various leaves, and each type of wreath meant something different. We're talking about the "corona triumphalis," made of laurels and used to indicate a triumph. If you want to know more about the other types of wreaths, click here.)
Have you ever heard someone say, "Don't rest on your laurels" when warning another person not to get too cocky after a big win? Well, now you know where that comes from – the phrase references none other than the laurel wreaths that were awarded for a victory. It's kind of weird that what started out as a symbol of Apollo's defeat in love became a symbol of human victory.