There's a Mexican legend that explains how it got associated with Christmas. A child (some sites say a girl, some a boy) couldn't afford a gift for Christ on Christmas Eve. So she picked some weeds from the side of the road. The child understood that the gift didn't need to be great. It just had to be given with love and would be acceptable in God's eyes. When she brought the weeds into the church, it blossomed into red and green flowers!
The Mayan Indians believed that poinsettias are powerful creatures from another world while the Aztecs saw the poinsettia as a symbol of purity. Today, we know the poinsettia to be Christmas flowers. And the best part is... that the red really goes well with the Christmas decor!
P.S - Before I forget, just like other flowers, poinsettias are good for gifting! But, if your loved ones are far, make use of this ecard site to wish them a pre-christmas gift with a bunch of love!