The poinsettia (Euphorbia pulcherrima) is a popular holiday plant first introduced to the United States around 1825 by Joel Poinsett. As of 2009, the poinsettia represented over 85 percent of all potted plants sold during the holiday season. They are often discarded after the holidays are over, but with the proper care, poinsettias may stay red until Valentine's day and even thrive throughout the year until the next Christmas season.
Choose a poinsettia that looks healthy with no signs of infestation or leaf damage. Avoid plants that have wilted leaves or broken stems. Inspect the bracts (the bright-colored red petal-like leaves) for signs of infestation and make sure the flowers (which are actually small and yellow) are intact.
The poinsettia is at its peak for blooming during the holiday season and requires little care at this time, other than water and a warm, sunny location. Water should be given when the soil becomes dry to the touch and it should receive enough water to thoroughly wet the soil. Because pots are often decorated in colorful foil for the holidays, once the poinsettia is brought home, the foil should be removed or cut to allow drainage, as poinsettias may develop root rot if they stand in water.
Spring and Summer
The poinsettia may be moved outside to a spot with partial shade once temperatures have risen above 60 degrees F and may be left there until the end of August or beginning of September. At the start of May, cut the stems back 3 to 6 inches from the soil to begin preparing it for the next holiday season. New growth will appear that should be pinched back in July to help form the size and shape of the plant. This will leave 4 to 5 leaves on each stem. Rinse away any milky sap from the plant that appears during the pinching. Another pinching may be needed again to continue shaping the plant in the middle of August.
To initiate the red color of the poinsettia by Christmas, the plant must have eight to 10 weeks of "short days" where it receives less than 12 hours of daylight. Place the poinsettia in a dark area from 5 p.m. to 8 a.m. and in the sun from 8 a.m. to 5 p.m. Once the color has started to form, it will no longer need to be kept in the darkness. Continue watering as normal during this time.
It is best to repot the poinsettia after the stems have been cut back in May. Select a pot that has good drainage and use a rich humus soil with a pH of around 5.5. Water the plant thoroughly after it has been transplanted. If additional plants are desired, the cutting from the stems may be rooted by placing them in moist perlite soil or sand.