Poinsettia's correlation with Christmas began in the 16th century with the legend of the young girl who was too poor to afford a gift for Jesus's birthday. She found weeds (at the urging of an angel) and placed them at the church altar, where they bloomed crimson. The star shape of the plant suggests the North Star and the crimson color signifies Christ's sacrifice of his blood.
Today, Poinsettia's come in various colors, but there is still a correlation between Christmas.
Here's some methods to make your own paper Poinsettia.