Poinsettia plants are native to Central America, especially an area of southern Mexico known as Taxco del Alarcon where they flower during the winter.
The ancient Aztecs called them "cuetlaxochitl." The Aztecs used the flowers (special types of leaves known as bracts) to make a purple dye for clothes and cosmetics; the milky white sap was made into a medicine to treat fevers. Today, we call the milky white sap latex.
The poinsettia was named for Joel Roberts Poinsett, the first United States Ambassador to the newly independent Republic of Mexico from 1825 to 1829. He was also a keen botanist and gardener and sent the poinsettia to America. The poinsettia — whose color comes not from its flowers (which are an insignificant yellow), but from its brilliant bracts — was used in Mexico to decorate churches at Christmastime and was called "flor de la noche buena," or “Nativity Flower.”
■ Place the poinsettia in a sunny window.
■ Do not let any part of the plant touch cold window panes.
■ Indoor temperatures from 60-70 degrees are ideal for long plant life.
■ High temperatures will shorten the life of the colorful bracts.
■ Water only when the soil is dry.
■ Placing your poinsettia in a cool room (55-60 degrees) at night will extend blooming time.
■ Do not fertilize when plant is in bloom.
■ Avoid temperature fluctuations and warm or cold drafts.
Remove any foil wrap that cover the pots drain holes before watering. It is best to set the pot in a saucer to catch the surplus water. Empty the saucer after watering. Water only when the soil is dry, but do not let the poinsettia wilt.
Make it bloom
Keep your poinsettia in total darkness between 5 p.m. and 8 a.m. to encourage it to flower. Start this around October 1 and continue until color shows on the bracts (large green leaves), usually around early- to mid-December.
Any little exposure to light can prevent flowering. Covering the plant with a light-proof bag and placing it in a closet might work. Nighttime temperatures above 70-75 degrees can delay or prevent flowering.
Moving plants outside
A poinsettia plant can go outdoors when all danger of frost has passed. Place it in a sunny area where it will get moderate shade in the afternoon. Fertilize once a month with a water-soluble houseplant fertilizer.
Since around 1919, an unsubstantiated tale has circulated concerning the alleged poisonous nature of poinsettias.
To alleviate the public's fear, the Society of American Florists and Ohio State University conducted a scientific investigation into the safety of the poinsettia plant. The Ohio State University research on the poinsettia plant effectively disproved the charge that the poinsettia is harmful to human and animal health. Of course, the poinsettia, like all ornamental plants, is not intended for human and animal consumption.