Poinsettias bloom in response to an uninterrupted dark period each day. They must have at least 13 hrs of continuous dark during a 24 hour period. A cool spare room in which you never turn on the lights is ideal. Some people put the plant in a closet every night and bring it back out in the day. Or you have to figure out some other way to shield the plant from ANY artificial light every night. As little as light from a porchlight or security light can prevent blooming. Obviously this is a challenging plant to re-bloom but many people are successful. The shade treatment is usually started in mid-October to have plants in bloom by December. If you starting now, it will take 6 weeks or so to have them in bloom. The temperature during the dark period should be about 60-62 degrees F. It's a lot of work, but being able to say "I did it" has a lot of satisfaction.
