The Greeks made wreaths of olive or laurel leaves, and gave them as prizes at the original Olympics. That's where the expression "don't rest on your laurels" comes from. (It means, don't stop striving to do better.)

When Julius Caesar became emperor of the Roman Empire, his generals placed a laurel wreath on his head as a crown. In fact, our word "crown" comes from the Latin word "corona," which means "wreath" or "garland." Eventually this custom evolved into crowns of gold and jewels.