The poinsettia, or Euphorbia pulcherrima, is a globally recognized symbol of the holiday season, primarily due to its striking, vibrant colors. Many people enjoy the plant for its impressive display, only to become frustrated when the beautiful red, pink, or white hues begin to fade, reverting to a simple green. This color change is not a sign of a dying plant but rather a natural biological process being disrupted by the typical indoor environment. Understanding the plant’s unique anatomy and needs is the only way to successfully maintain or restore the seasonal color.
Bracts, Not Leaves: The Source of Poinsettia Color
The colorful structures on a poinsettia are specialized, modified leaves called bracts, not the true flowers or typical leaves. The actual flowers are the small, yellow-green structures found clustered in the center of the bracts. These bracts are essential for attracting pollinators in the plant’s native environment.
The vibrant colors are produced by pigments called anthocyanins, which accumulate in the bracts. Crucially, these same bracts also contain the green pigment chlorophyll, which is present in all varieties. When the plant is in its green, vegetative growth phase, chlorophyll masks the underlying anthocyanin pigments. The process of “turning color” is the plant decreasing chlorophyll production while simultaneously accumulating anthocyanins in response to environmental cues.
The Critical Role of Light and Darkness
The primary factor controlling the poinsettia’s color change is a phenomenon known as photoperiodism. Poinsettias are “short-day” plants, meaning they require a specific, long period of uninterrupted darkness each day to trigger the production of colorful anthocyanin pigments. This mechanism allows the plant to naturally time its coloration and flowering for the short days of winter. This specific period must consist of 12 to 14 hours of absolute darkness daily, maintained for about eight weeks.
The green reversion occurs when this darkness cycle is broken, even briefly, by artificial light. A few minutes of light exposure from a streetlamp, a television, or even a cell phone screen is enough to disrupt the chemical signaling process. When the dark period is interrupted, the plant stops the specialized pigment production and instead prioritizes chlorophyll synthesis. The loss of the vivid color is simply the green chlorophyll pigment taking over once the anthocyanin production is halted.
Adjusting Care to Prevent Green Reversion
To prevent the color from fading or to coax a green plant back to its holiday hue, a strict schedule must be implemented. The process of re-coloring must begin around October 1st and continue consistently for approximately eight weeks. The plant must receive 14 hours of absolute, uninterrupted darkness every single night.
You can achieve this by placing the plant in a dark closet, under a large cardboard box, or inside a black trash bag from roughly 5:00 p.m. to 7:00 a.m. the following morning. The total absence of light is non-negotiable; even a sliver of light can sabotage the effort. During the remaining 10 hours of the day, the poinsettia needs bright, direct sunlight to sustain healthy growth and fuel the eventual color change.
While light is the main control, other factors can stress the plant and accelerate color loss. Poinsettias prefer indoor temperatures between 65 and 70 degrees Fahrenheit. Exposure to cold drafts or temperatures below 50 degrees Fahrenheit can cause damage and leaf drop. Proper watering is also necessary; the soil should be kept consistently moist but never waterlogged, as constant wetness leads to root rot. By controlling the light cycle and maintaining a stable environment, you can encourage the vibrant bracts to remain colorful throughout the holiday season.