Poinsettia

Euphorbia pulcherrima is a shrub or small tree, typically reaching a height of 0.6 to 4 m (2 to 16 ft). The plant bears dark green dentate leaves that measure 7 to 16 cm (3 to 6 inches) in length. The colored bracts—which are most often flaming red but can be orange, pale green, cream, pink, white or marbled—are often mistaken for flower petals because of their groupings and colors, but are actually leaves. The colors of the bracts are created through photoperiodism, meaning that they require darkness (12 hours at a time for at least 5 days in a row) to change color. At the same time, the plants require abundant light during the day for the brightest color.
The flowers of the poinsettia are unassuming and do not attract pollinators. They are grouped within small yellow structures found in the center of each leaf bunch, and are called cyathia.