Poinsettia plants (Euphorbia pulcherrima) remain one of the most popular holiday flowers. The familiar red blooms have been joined by even flashier colors. Actually, they are not flowers but modified leaves called bracts. The bright bracts are designed to attract insects to the tiny yellow flowers in their centers. Hybridizers have expanded the range of colors from the familiar red to pastel yellow and vibrant bicolors. Because poinsettias have been forced into bloom, they need some extra care to keep them in bloom throughout the holidays. While it may be easier to buy new plants each year, it is possible to get them to rebloom the next season.