Many people wonder what makes poinsettias turn red. It is actually the plant’s leaves that provide its color through a process called photoperiodism. This process, in response to certain amounts of light or lack thereof, turns the leaves from green to red (or pink, white, and other shade variations). What most people mistake as flowers, in fact, specialized leaves, or bracts. The small yellow flowers are found in the center of the leaf branches.
To coax a poinsettia plant to bloom again, it’s necessary to repeat the poinsettia life cycle. After the holidays and once blooming has ceased, limit the amount of watering so the plant can go dormant until spring. Then, usually around March or April, regular watering can be resumed and fertilizing can begin. Prune back the plant to about 6 inches from the top of the container and repot. Poinsettia plants can be kept outdoors in a protected sunny area during summer if desired. Pinch out the tips to promote branching of new growth until about the middle of August. Once fall returns (and shorter days), reduce the amount of fertilizer and bring outdoor plants inside. Once again, limit watering in September/October and give the poinsettia bright daylight temperatures between 65-70 F. (16-21 C.) with total darkness at night with cooler temperatures of around 60 F. (15 C.). Once flower bracts have developed definite color, you can reduce the amount of darkness and increase its water.