One of the pleasure nearing the Christmas season is the flood of Poinsettias everywhere. The plant also goes by the name Christmas Star, not surprisingly as the dentate shape of the vibrant bracts form a blazing star, which remind us so clearly of the Star of Bethlehem, that Franciscan friars in Mexico included it in their Christmas celebrations as early as the 17th century. 
Other legend has it’s first association with the Christmas season in the story of a girl in Mexico, too poor to celebrate the birth of Christ, she gathered weeds along the side of the road and put them on the church’s alter where later beautiful crimson Poinsettias sprouted in abundance.
More specifically, Euphorbia pulcherrima meaning “the most beautiful Euphorbia” derives its common English name from Joel Robert Poinsett, the first US Minister to Mexico who during the mid 1820 was traveling in the area of Taxco del Alarcon where Joel Robert first noticed what the locals called “Flor de Noche Buena” or Christmas Eve flower. Intrigued (as he also was an avid amateur botanist), he started sending samples back home to the States where the plants did well on his plantation in South Carolina and by 1836 the American name for the plant was Poinsettia.
In Nautl which is the language of the Aztecs, Poinsettias were called Cuetlaxochitl It represented purity. The name signified “mortal flower that perishes and withers like all that is pure.” 
This shrub or small tree can grow up to 13 feet in it’s native environment where the climate is mild with average highs around 81°F and average lows around 63 °F, all year long. The dry season is October to May and rains typically occur from June to September. Long nights and short days are then the catalyst that stimulates the green bracts to change color (photoperiodism) and by mid December the bright crimson “blooms” emerge. More modern hybrids come in choral, pale green, cream, pink, white, marbled, splashed or speckled varieties. The actual flowers are called cyathia and consists of a group of small yellow structures that can be found in the center of each leaf bunch (bracts) but they do not attract any pollinators.
In areas outside its natural environment, it is commonly grown as an indoor plant where it prefers good morning sun and shade during the hotter part of the day.
Potted Poinsettias
Paul Ecke Sr as well as Jr. are the family that mostly is responsible for the Poinsettia industry the USA. They developed a grafting technique that produced a much more attractive plant and nowadays most plants for the USA are grown from cuttings. In order to produce a plant with multiple flowers a phytoplasma infection is used, this infection triggers the plant to produce many axillary buds.
When choosing a Poinsettia look for a plant with dark green leaves all the way down to the soil level and make sure there is no pollen on the cyathia. The plant also should be in proportion to the pot it planted in.
When you bring home your plant, be mindful not to expose the plant to temperatures below 55F even for a short time, it will cause the Poinsettia to wilt and drop it’s leaves and at that point there is not much to be done than to clean up the mess and find another plant.
To keep your plant looking good keep the soil moist but not soggy, and place in a room with sufficient natural light with temperatures around 60 to 70 degrees F. Make sure the plant does not touch any window panes and keep it away from cold or warm drafts. Water thoroughly when the soil begins to dry but be sure to drain off excess water to prevent root-rot.
The use of Poinsettia as potted plants is widespread and often is used for Christmas foliage and color.
For information on how to grow Poinsettias from cuttings click here.
Here is a very good reference on How to get your Poinsettia to re-bloom.
Cutflowers
To use the Poinsettia as a cut flower you want to find the freshest blooms on a plant with foliage all the way to the ground. Look for green- or red tipped cyathia and avoid bracts with cyathia that have yellow pollen, this is a sign that the plant is older.
Remove leaves of lower part and cut stem at a slanted orientation with sharp knife, now sear the end with a flame for a few seconds, this will seal in the milky sap. Place stem in lukewarm water and add a floral preservative. Let stand in cool room to drink and after an hour refresh water if it looks milky, a little bit of sap may still seep where leaves were removed. When water is clear the stem can be used in fresh cut arrangements and will last up to two weeks in water provided they are not exposed to excessive heat, cold or drafts.
Medicinal
The Aztecs referred to the winter-blooming plant as cuetlaxochitl and used the plant to produce red dye and also as an antipyretic medication.
Although not backed up by scientific evidence of it’s effectiveness, Poinsettia has been mentioned in the use of folk remedies for fever, pain, infection, warts, skin disorders and toothache.
Many plants in the Euphorbia family are poisonous but the toxicity of Euphorbia pulcherrima is relatively mild, it’s latex may cause an allergic reaction in sensitive people and also may cause diarrhea or vomiting. Sap in the eye could cause temporary blindness.
Poinsettias are susceptible to several diseases, mostly fungal, but also bacterial and parasitic. Here is a good link to the most common problems for Poinsettias.
