Poinsettias, scientifically known as Euphorbia pulcherrima, are recognized globally for their vibrant holiday color, which is often mistaken for a flower. This coloration is the source of a misunderstanding about the plant’s true botanical structure. The large, brightly-hued portions that draw the eye are not petals. This popular plant has a unique reproductive strategy that relies on a colorful masquerade to attract necessary pollinators.
The Colorful Deception: Understanding Bracts
The poinsettia’s decorative appeal comes from specialized leaves called bracts, not flower petals. These bracts emerge at the stem’s tip, surrounding the plant’s much smaller, true flowers. Their purpose is to visually compensate for the flowers’ lack of showiness, mimicking a large bloom to lure insects.
The bright color of the bracts (red, white, pink, or marbled) is achieved through photoperiodism. This process requires long periods of uninterrupted darkness, typically 14 hours per night for six to eight weeks, to trigger the color change. Unlike delicate petals, these bracts retain the ability to photosynthesize.
The bracts are highly sensitive to environmental stress, possessing an abscission zone that causes dropping when exposed to cold drafts or improper watering. This sensitivity explains why a poinsettia can lose its colorful display quickly after being moved from a warm store to a chilly car or home.
Locating the True Poinsettia Flower
The true flowers of the poinsettia are found in the center of the colorful bracts. These small, cup-like structures are botanically referred to as cyathia, which is characteristic of the entire Euphorbia genus. A cyathium is an inflorescence containing both male and female flower parts that lack petals and sepals.
The cyathia are typically yellowish-green and may have glands that secrete nectar to entice pollinators. Their appearance is a reliable indicator of the plant’s freshness and longevity in a home environment. Once the cyathia begin to shed their pollen, the plant’s reproductive cycle is nearing completion.
After the cyathia finish their role, the surrounding bracts will soon begin to drop. Many modern cultivars have been bred to retain their bracts longer. The presence of fresh, firm cyathia remains the most accurate way to judge the plant’s health and ornamental value.
Beyond the Botany: Common Poinsettia Facts
The common name “poinsettia” honors Joel Roberts Poinsett, who introduced the plant to the U.S. in the 1820s while serving as the first U.S. Minister to Mexico. Native to Mexico and Central America, the plant grows naturally as a woody shrub or small tree. Its indigenous Nahuatl name is cuetlaxōchitl, meaning “flower that grows in soils.”
A misconception surrounds the plant’s toxicity. This belief stems from an unverified story from 1919, but scientific research and data from poison control centers debunk this claim. The plant is considered to have low toxicity, posing little danger to children or pets.
The milky white sap, known as latex, can cause mild stomach upset, including nausea or diarrhea, if consumed. Contact with the sap may also cause a skin irritation or rash in sensitive individuals. A serious toxic effect would require ingesting hundreds of leaves, which is unlikely due to the unpleasant taste.