The poinsettia (Euphorbia pulcherrima) is known almost all over the world as the flower of Christmastime. Growing naturally in Mexico, this plant was named for Joel Poinsett who introduced them into the United States in the early 1800's when he was U.S. ambassador to Mexico. The poinsettia ranked number one in 1990 in the United States when compared with other potted flowering plants. The wholesale value of poinsettia in the United States for that year was $183.5 million.

Poinsettia flowers are small golden cups, known as cyathia, at the center and top of the plant. The red, pink, or white bracts (modified petal-like leaves) provide the coloring.

This plant needs a rich well-drained soil and adequate light. If the light is sufficient for reading, it will be sufficient for the poinsettia. Protection from direct south or west sun and hot and cold drafts must be provided. As a house plant the Poinsettia prefers a night temperature of 60 to 65 degree Fahrenheit and a 65 degree Fahrenheit day temperature. When grown in the greenhouse under full sun, this plant should have the same night temperature but should have day temperatures about 70 degrees Fahrenheit (21 degrees C.) on cloudy days and a temperature of 75 to 80 degrees Fahrenheit on sunny days. The soil should be kept uniformly moist, possibly requiring water two or three times a week or more often. In a warm house in late winter, this plant often loses its leaves unless watered almost daily. Every two to three weeks while blooming, water with a solution of 1 teaspoon houseplant fertilizer per gallon of water.

Reduce the amount of water applied after blooming has ceased, and allow the plant to go dormant. During this period, a cooler temperature is permissible, but not below 50 degrees Fahrenheit .

When the weather warms in late spring repot the plant. Bury the pot up to the rim in an area of the garden receiving full sun. Prune at this time to produce a more shapely plant. Usually after a winter of blooming, poinsettias are very leggy. Keep the plant short and compact by pinching out the tips of all new shoots that develop until the middle of August.

Water the plant with a solution containing one teaspoon of soluble fertilizer per one gallon of water every two weeks throughout the summer. Since poinsettias are very sensitive to cold, bring the potted poinsettias into the house well before the first frost.

Start new plants during the summer by allowing the shoots to become three to five inches long and then remove them. Root them in a pot of sterilized sand.

Poinsettias are plants that show a photoperiodic response. In this case, these plants demand at least 12 hours of absolute darkness each evening to bloom. This requirement is easily supplied, starting October 1, by slipping a light-tight box over the plant at 5:00 p.m. and keeping it in place until 8 a.m. This provides a "night" that is 15 hours in length - more than enough to induce flower bud formation. It is important that the cover be light-tight. Only 5 minutes of light an evening from a 60-watt bulb will delay flowering by two weeks. Continue to water and fertilize during this period.

Commercial greenhouses pull a photoperiodic blackout shade cloth over the crop each evening at 5:00 p.m. and remove it at 8:00 a.m. the next morning to produce this "long-night" requirement. In the more northern climes where darkness reaches the 12 hour period in late fall, the use of shade cloth or other shading devices may not be necessary unless other light sources are present that will prevent flower bud formation.

Continue to cover the plant each evening until color begins to show in the top leaves. If these requirements have been met, color should develop in the uppermost leaves starting in the third week of November.

Additional internet links on the poinsettia include:
The facts about Poinsettia - they are not poisonous
The Poinsettia - University of Nebraska
The Poinsettia - Texas A & M University

References include:
McDonald, E. 1993. The New Houseplant: Bringing the Garden Indoors. Macmillan Publishing.
McMahon, R.W. 1992. An Introduction to Greenhouse Production. Ohio Agricultural Education Curriculum Materials Service. - Includes detailed production information.

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