Poinsettias remain one of the most popular holiday flowers. Hybridizers have expanded the range of colors from the familiar red to pastel yellow and vibrant bi-colors. One of the most common questions after Christmas is “How can I care for my poinsettia so that it will bloom again next Christmas?”. While this can be done, it's a very fussy, exacting process and since the plants are not that expensive, you might just choose to start fresh next year.
For those of you who are undaunted, the process for saving your poinsettia and getting it to rebloom begins with the care you give it the first season.
When You First Bring Your Poinsettia Home:
Light - Place it near a sunny window. South, east or west facing windows are preferable to a north facing window. Poinsettias are tropicals and will appreciate as much direct sunlight as you can provide.
Heat - To keep the poinsettia in bloom as long as possible, maintain a temperature of about 20°C during the day. Dropping the temperature to about 16°C at night will not hurt the plant. However, cold drafts or allowing the leaves to touch a cold window ca injure the leaves and cause premature leaf drop. If you've ever see a gangly poinsettia in bloom, with only a couple of sad looking leaves hanging on, it was probably exposed to temperatures that were too cool or extreme shifts in temperature.
Water - Water the plant whenever the surface feels dry to the touch. Water until it drains out the bottom, but don't let the plant sit in water. Wilting is another common cause of leaf drop. A wilted plant can be revived and salvaged, but it will take another season to improve its appearance.
Humidity - Lack of humidity during dry seasons, in particular winter, is an ongoing houseplant problem. If your home tends to be dry and your poinsettia is in direct light, you will find yourself watering frequently, possibly every day
After Christmas Care:
January - March: Keep watering the poinsettia whenever the surface is dry.
October: Poinsettias are short-day plants, meaning their bud set is affected by the length of daylight. To re-bloom, poinsettias need about 10 weeks with 12 hours or less of sunlight per day. You will have to artificially create these conditions and it's crucial that you be diligent. Beginning October 1st, keep your plant in complete darkness from 5 pm to 8 am. Any exposure to light will delay blooming. Use an opaque box or material to block out light. Many people place their plants in a closest, but if light gets in though the cracks or if you open and use the closet, it will affect the bud set. Move the plant back to the sunny window during the daytime and continue watering and fertilizing
November: Around the last week of November, you can stop the darkness treatment and allow the plant to remain in the window. You should see flower buds at this point
December - Stop fertilizing about December 15th. Keep watering and treat your plant the way you did when you first brought it home in bloom. If all has gone well, it should be back in bloom and ready to begin the process all over again.