Brilliant poinsettias in full bloom flood the U.S. market in early December, promising crimson flowers--actually, leaves--to brighten the Christmas holidays. Although they look care-free, these tender perennials require specific growing conditions to produce blooms at Christmas. Once blooming ceases, red leaves drop and are replaced by deep green foliage for the remainder of the year. Poinsettias can be grown as a houseplant---or summered outside--and forced to bloom again the following winter.
Place poinsettias in bright, direct indoor light during the winter. Water when the soil dries.
Transplant the poinsettia to the garden or set pots outside once the weather warms and all danger of frost has passed in your area.
Water deeply once a week and apply water-soluble fertilizer designed for houseplants once a month.
Move poinsettias inside in late summer or early fall when temperatures dip below 60 degrees Fahrenheit at night.
Cover the foliage with a cardboard box, wrap with lightproof paper or place the poinsettias in complete darkness for 12 to 14 hours a night, beginning in late September. Stray light from nightlights, outside streetlights or even a bathroom light turned on for a few minutes during the night inhibit blooming. Maintain temperatures between 55 and 70 degrees Fahrenheit at night.
Uncover the poinsettia during the day and place it in a bright window. Water when the soil dries slightly.
Move to the poinsettia into light once color begins to develop on the leaves in early to mid-December. Uncover completely by December 15, even if color is not yet evident.