A: If you obtain a poinsettia for your home, place it near a sunny window where it will have the most available sunlight. A window that faces south, east or west is better than one facing north.
To determine when to water your plant examine the soil daily, and when the surface is dry to the touch, water the soil until it runs freely out the drainage hole in the container. If a saucer is used, discard the water that collects in it. Do not leave the plant standing in water.
To keep the plant in bloom, maintain it at a temperature of 65 to 70 degrees F during the daylight hours and, if possible, move it to a cooler place at night. Avoid exposing the plant to hot or cold drafts, which may cause premature leaf drop.
Poinsettias can be reflowered the following Christmas, but unless a yearlong schedule of care is observed, the results usually are not good. For such a schedule, continue normal watering of the soil until the first of April, then allow it to dry gradually. Do not let it get so dry at any time that the stems shrivel. Following the drying period, store the plant in a cool, airy location on its side or upright. In the middle of May, cut the stems back to about 4 inches above the soil, and either replant in a pot 1 to 2 inches larger in diameter or shake old soil off the roots and repot in the same container. In early June, leave the plant in the pot, move it outdoors, and place it in a lightly shaded location. Continue watering and fertilizing the plant while it is outdoors. Remove 1 inch of terminal growth in early July. Then, between August 15 and September 1, cut the new stems back, allowing three or four leaves to remain on each shoot. After this bring the plant indoors and again place it near a window with a sunny exposure.
Poinsettias are short-day plants, which means they flower about 10 weeks after the daylight shortens to about 12 hours or less. Therefore, to have the plant in full flower by Christmas, keep it in complete darkness between 5 p.m. and 8 a.m. from the first part of October until Thanksgiving.
Various reports over the years have led the general public to believe poinsettias are toxic to humans; however, this has not been authenticated. Research conducted at The Ohio State University and other institutions has proved the old wives' tale that poinsettias are poisonous to be false.
Excerpts from Ohio State University Extension Fact Sheet, Poinsettia Care in the Home: HYG-1248-96, McMahon, et al. For specific information contact your local county extension office