The Poinsettia, or Euphorbia pulcherrima has been considered as one of the symbols of Christmas. It's name "Poinsettia" is named after Joel Roberts Poinsett, the first United Minister to Mexico, who introduced the plant to US in 1828.
The plant is called Cuetlaxochitl (skin flower) by the Aztecs in their language. The Aztecs used the plant as antipyretic medication.
Today, this plant is known as "Noche Buena" in Mexico and Guatemala which means Christmas' Eve. In Chile and Peru, the plant became known as "Crown of the Andes." In Spain, it is known as "Flor de Pascua" or Easter Flower.
It was believed in Mexico in 16th century that there was a young girl who too poor to give a gift for the celebration of Jesus' birthday. According to the legend, the child was inspired by an angel to gather weeds from the roadside and place them in front of the church altar. To their surprise, crimson blossoms sprouted from the weeds. It became beautiful poinsettias. It was in 17th century when the Franciscan friars started to include poinsettias in their Christmas celebrations.
In the US, poinsettias are typical Christmas decorations in homes, churches, offices and elsewhere. It is available almost everywhere like in grocery, drug and hardware stores. US celebrates the National Poinsettia Day in December 12.