Answer: Poinsettias are induced into blooming by shorter daylength. In late September begin placing the plant in total darkness for 13 to 14 hours every night. The spot must be really dark -- no streetlights shining in, no occasional visitors turning the lights on. A dark, unused closet is a good spot. Each morning, bring the plant out and place it in bright light for the remaining 10 or 11 hours, placing it back in the closet each evening. This will give them the short days they need to trigger the response to color up in time for the holidays.
Keep and eye on the plant, and when the bracts have started showing color again -- usually about 4 weeks -- you can stop the nightly ritual and treat them like any other houseplant. Place then in a bright spot and keep soil evenly moist but not soggy.
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