Poinsettia is the common name of Euphorbia pulcherrima a small shrub-like plant native to Mexico. It is popular in the United States as a decorative plant, particularly during the Christmas season, and has become a common symbol of this holiday in the United States and other countries as well. Poinsettias are admired for their colorful leaves and bracts, which are often mistaken for flowers. A rich, deep red is the most common color for the bracts on a poinsettia, which contrast with their attractive dark green leaves. A white poinsettia is a cultivar of this species with white bracts instead of red.
In Mexico and other parts of the world, poinsettia plants are known by a variety of other names. The name poinsettia is popular in the United States as a tribute to the American diplomat, Joel Poinsett, who first brought them from Mexico in the early 19th century. The tradition of these plants being given as gifts and used as decorative accents during the Christmas season is much older, however, and is believed to date from the very earliest European colonies in what is now Mexico. Poinsettia attained its popularity as a symbol of the Christmas season in the United States in the 20th century.
The colored leaves of a poinsettia plant are a result of a phenomenon called photoperiodism. When the plant is subjected to conditions in which a certain ratio of daylight to darkness is reached, the specialized leaves, called bracts, at the terminal ends of growing stems change color, which in nature is a rich crimson or red color. A poinsettia plant must have at least 12 hours of darkness for 5 to six consecutive nights to achieve this effect. Growers manipulate conditions to force their poinsettia plants to exhibit the color changes in the bracts. White poinsettia plants have bracts that turn white instead of red.
Bract colors in poinsettia can vary significantly, as over one hundred named varieties are cultivated commercially. Reds, fiery oranges, pastel shades of pink or green, and even mottled or marbled bract colors are possible. A white poinsettia can have a color ranging from bright white to shades of off white, cream, or ivory. The color of the bracts is a product of selective breeding for desired characteristics, as is done with many flower and plant species. All white poinsettia plants will have standard leaves with a similar deep green color, but what one grower may market as a white poinsettia may have a significantly different shade than another white poinsettia.