If your poinsettias are still looking so good you can’t bear to throw them away, follow these tips to keep them for next year.
On St Patricks Day, cut off blooms leaving 4 to 6 leaf nodes on the stem. When the ground warms up, plant your poinsettia outdoors in a half-day sunny spot. Water and fertilize regularly with any well balanced fertilizer. By May you should see new growth. Pinch back your plant on July 4th, and again on Labor Day if needed to keep it short and bushy. To be sure that your poinsettia blooms at the right time next year, remember that poinsettias need 12 to 14 hours of complete darkness for the plant to decide to bloom.
September 21 starts the 12 hour night. Temperature and any artificial lights also have an impact. You can bring your plant into bloom earlier by putting a big box over it or you can put your poinsettias in the closet each night for some extra hours of darkness. Keep this up for 8 to 10 weeks or until bracts begin to color.