What most of us consider the flower part of a poinsettia are really bracts surrounding the small, inconsequential flowers.

In their native growing areas of Mexico and Central America, these are flowering shrubs and can grow as high as ten feet.

The legend of the poinsettia is a young peasant girl in Mexico was too poor to afford a Christmas gift to offer in celebration of the birth of Christ at the church and picked some roadside weeds as her humble gift. When she arrived, the 'weeds' bloomed into colorful flowers.

37 minutes ago, Bill W said:

Besides the red poinsettia you may see, there are white poinsettias as well.  

Also orange, green, pink and white, and salmon.

Poinsettias don't have seeds. They grow from cuttings.