Known for their eye-catching red and green foliage, poinsettias (Euphorbia pulcherrima) are a popular flowering plant, particularly during the winter holidays. The fact that poinsettia blooms are not flowers in the conventional sense, however, surprises a lot of people. Rather, they are curious-looking structures called cyathia that consist of a single female flower and many male flowers, along with yellow bulbous glands that vaguely resemble mouths.

Cyathia are unique to the Euphorbia family of plants, which includes the poinsettia, as well as many other species of succulent and cactus-like plants. Unlike traditional flowers, cyathia lack petals and sepals. Instead, they have a cup-shaped structure, called an involucre, that surrounds the reproductive parts of the flower.

Despite their unique reproductive structures, poinsettias are still able to produce viable seeds. However, because they are often grown as ornamental plants, they are typically propagated vegetatively, through stem cuttings or tissue culture.