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You can learn a lot about botany from that poinsettia you've brought home as Christmas decoration.

Bringing a poinsettia home this holiday season? These horticultural facts may make you look at this beloved holiday decoration a little differently.

A not-so-natural history

The foil-covered, potted poinsettia that we know bears little resemblance to its wild ancestor, which grows as a lanky shrub in hot, dry areas of Mexico. The plant was introduced to America in 1828 by Joel Roberts Poinsett, the first United States Ambassador to Mexico. However, credit for making the poinsettia one of the most popular indoor plants belongs to the Ecke family of California.

In the early 1900s, Paul Ecke Sr. sold the brightly colored plants from roadside stands in Hollywood. His son, Paul Ecke Jr., was responsible for breeding plants that withstood shipping and produced long-lasting blooms. Ecke Jr. escalated poinsettia’s popularity by donating them to fashion magazine shoots and holiday sets for TV broadcasts, such as “The Tonight Show” and Bob Hope Christmas specials.

Bracts can be beautiful

The colorful parts of the poinsettia are not flower petals but bracts. These leaf-like structures are similar to the white and pink parts that surround dogwood blossoms. Though not very noticeable, the actual flowers of poinsettias are contained within the small yellow-green globes in the center of the bracts.

Poinsettias are infectious

The original potted poinsettias were a single bloom on a compact plant. The beautiful, multi-bloom plants that we know today are the result of phytoplasma — an organism similar to bacteria found in the tissues of some poinsettia plants. Growers discovered that this organism lived in plants with the dense and branching characteristics that were desirable in a potted poinsettia. Today, infected plants are grafted to transfer this desirable “disease.”

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An organism called phytoplasma is responsible for the dense and branching characteristics so desirable in a potted poinsettia.

A poinsettia’s inner clock

Poinsettias are short-day plants, meaning that waning daylight triggers the flowers. Despite the term short-day, it is really the length of night, or darkness, that is important in the blooming cycle. In order to flower for the winter holidays, a poinsettia needs 12 to 14 hours of darkness each day, beginning around Oct. 1. Even a short light interruption during the dark period (for example, the accidental flip of a light switch) can reset the clock and prevent the poinsettia from blooming.

Poinsettias as house guests

Poinsettias are not poisonous, despite what you may have heard. They probably acquired this reputation because they have a milky sap irritating to those with latex sensitivity. Chewing on poinsettias will not kill Fluffy or Fido, but it’s best to keep poinsettias away from young pets, as ingested leaves may cause stomach discomfort in a small animal.

As the days get longer, poinsettias’ colorful bracts will fade and green leaves will replace them. They make a nice patio plant, but will be extremely difficult to re-bloom in fall, due to reasons described above. When your green and lanky poinsettia has outstayed its welcome, give yourself permission to compost it and purchase a new one next holiday season. With over 100 poinsettia cultivars to choose from, you might want to explore a different color or form to add to your holiday decorations next year!

Lois Miklas is the coordinator of the Penn State Master Gardener Program in Lancaster County.

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