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A blooming poinsettia is a symbol of Christmas.

Once considered a weed in its native Mexico, today the poinsettia is one of the top selling potted plants in the United States. A popular holiday plant, the poinsettia flowers in response to a short day, long night photoperiod. It naturally flowers during the fall season in Mexico.

The yellow flower in the center of the plant is a cyathium. Each plant has multiple cyathium in the center of the colored bracts. Each cyathium contains multiple male flowers and a single female flower. Poinsettias are monoecious, having male and female flowers located on the same plant, as opposed to dioecious plants that have male and female flowers on separate plants.

Poinsettias are available in a variety of colors, with red, pink and white most common but green, yellow and orange are also available. Red is still the most popular color, followed by novelty colors with bracts that are flecked, marbled or splashed with color.

The introduction of more compact varieties in the 1960s led to mass production and marketing of the holiday flower. Prior to this, the poinsettia was a greenhouse oddity used as a short-lived cut flower.

White varieties were first introduced in the 1970s. A trend has been to spray paint or spray glitter on white poinsettias, creating blue, purple and rainbow-colored plants that sparkle.

Plant breeders have been using selections of Euphorbia pulcherrima to create compact cultivars with increased longevity for years now. More recently, breeders have been creating interspecific hybrids by crossing traditional poinsettias, Euphorbia pulcherrima with Euphorbia cornastra. These hybrids have smaller cyathium putting the focus on the profusion of brightly colored bracts.

Euphorbia cornastra is known as the dogwood poinsettia. It was collected from Mexico in the 1990s. Blooming during the summer, the dogwood poinsettia has grey-green foliage with pure-white bracts.

The Princettia series is one example of an interspecific hybrid. The series has compact growth, dark green foliage and five flower colors: dark pink, hot pink, pink queen, red and pure white.

The hybrid Luv U Pink continues producing new layers of fluorescent pink bracts. It does not develop many cyathium, and those that do develop tend to drop before opening.

J’Adore has three shades of pink available. Hot Pink is not as fluorescent pink as "Luv-U-Pink," but still beautiful. J’Adore has large, open centers with many cyathium that drop anthers and pollen, making the plant somewhat messy. The plant has dark green foliage and strong uniform branching.

Dec. 12 is National Poinsettia Day, recognizing both the plant and the man who introduced poinsettias to the United States, Joel Roberts Poinsett. This lanky shrub from Mexico has come a long way since its introduction.

Check out a few of the hundreds of cultivars at the RCTC Horticulture plant sale. Visit our website at www.rctc.edu/program/hort/news-events.

Robin Fruth-Dugstad is a horticulture professor at Rochester Community and Technical College with 25 years of experience gardening and landscaping. Send plant and garden questions to life@postbulletin.com.

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