Taking Care of Poinsettias

Although the poinsettia is among the most traditional symbols of the Christmas season, it was cultivated by the Aztecs of Mexico long before the introduction of Christianity to the Western Hemisphere.
Poinsettias were first introduced into the United States in 1825 by Joel Robert Poinsett. While serving as the first U.S. ambassador to Mexico, he had occasion to visit Taxco, south of Mexico City where poinsettias grow wild on the hillsides. Poinsett, a botanist when he wasn’t a politician, had some plants sent to his home in Greenville, South Carolina. After supplying his greenhouses, Poinsett also distributed plants to various botanical gardens and to some friends including John Bartram of Philadelphia. John Bartram gave them to a nurseryman friend, Robert Buist, who saw the potential for commercial sales and began production of what turned out to be the largest greenhouse crop grown in the U.S.
Poinsettias are normally grown for sale at Christmas time but by control of photoperiod and temperature they can flower almost any time. Many who buy plants want to keep them from year to year and this is a good thing but there are some problems.
Poinsettias are quite sensitive to light. They need at least 11 hours and 45 minutes of darkness to cause flower bud initiation and you can get a quicker response if the hours are increased to 14 or 15. The problem is that exposures of light even as low as less than 2 foot-candles will nullify the effect of darkness. Homeowners who try to grow poinsettias from year to year grow them indoors and unfortunately common house lights at night will not allow flower initiation.
The other problem homeowners have growing flowering poinsettias is temperature. Poinsettias require night temperatures of 62- 64 degrees F to ensure the most rapid development under the correct photoperiods in late September and October. Most homes are kept at 68 F or better and without low temperatures the plants just keep growing leaves and not flowers. After 10-14 days of the correct photoperiod and temperature you can then raise the temperature to 67- 68F to favor bract development.
Why can’t we keep these wonderful plants and have flowers every year? I think you can see that it is not the plant but the way we try to grow the plant that prevents flowering.