If you have a green thumb, you may want to try your hand at reflowering your poinsettia next year. If you follow these directions and dates carefully, you may have your poinsettia in flower by next Christmas.
December: Full bloom-Enjoy for the holidays!
Water as needed by letting soil become just dry before adding water. Do not let poinsettias sit in water for any length of time as they are very sensitive to soggy soil. Color will last longest in a sunny, cool room away from both hot and cold drafts.
February through spring: Color begins to fade.
Cut stems back by about half in March. Keep near a sunny window, and fertilize as for any houseplant when you notice new growth.
Repeat trimming branches if necessary so plant becomes bushy. You can move the poinsettia to bright shade or morning sun/afternoon shade for the summer once danger of frost has passed.
Take it inside—cut stems back a final time, leaving 3-4 inches per shoot. Place in a sunny window, and water and fertilize as needed.
September 20 through December 1 (Important, EXACTLY these dates):
Keep in the window only from 8AM to 5PM. Put in the dark (NO LIGHTS) from 5pm to 8am. THIS IS THE KEY TO SUCCESS. You can move the plant into a dark, unused room, or place it in a large box that can be closed, but the poinsettia must receive no light at all.
If you have kept the poinsettia in the dark at the right times, you should see a hint of color beginning in the top leaves in mid- to late October. Stop fertilizing once you see the color begin, and don't resume until after Christmas.