Blooming a poinsettia is a wonderful challenge if you're up to it. The task itself is not terribly difficult, but it does require diligence and, during the crucial bud-set period, total black-out discipline. If this sounds right for you, follow these steps to bring your poinsettia back into bloom next Christmas.Resting After Christmas
After the holiday season is over, the plant will begin to gradually lose its leaves in anticipation of a resting period. Move the plant to a cooler, somewhat shadier location. Don't worry about the leaves falling—they're supposed to. Cut the water back, and only water when the soil is dry to the touch. Do not fertilize.
If you don't want to let the leaves drop naturally, feel free to cut the plant back hard when you move it to its resting place. Trim the branches to within a few inches of the soil, leaving only a naked stump.
Although your plant will look dismal, this is natural. The only word of caution is to watch the stems. Stems that shrivel or turn brown are dead.Spring Rejuvenation
In May, when the temperature outside is consistently 60 degrees or higher, move the plant from its resting place outside. At the same time, repot it into a slightly larger pot. Outside, the poinsettia wants dappled, but not direct, sunlight. For potting soil, use an organic potting mixture. Do not put the plant directly into the ground unless you plan to keep it there permanently (which is possible in higher USDA zones). Finally, resume watering and feeding normally.
You should see the plant begin to grow again. New leaves and shoots will appear.
As the summer wears on, selectively prune the plant to preserve three to four main branches. This is the same number professional growers usually aim for. You can use the cuttings to start new poinsettias.
By the end of the summer, you should have a healthy, somewhat larger poinsettia than the original plant. Now comes the tricky part.The Darkness
Like many plants, poinsettias set their flowers based on light cycles. To force a poinsettia into a Christmas bloom, you need to provide 12 hours of total darkness every day, beginning in late September or early October.
Total darkness means total darkness. Some people move their plants into closets at night, which will only work if there is absolutely no light pollution in the closet. Other people cover their poinsettias with black bags or boxes to shut out the light. During the day, move your plant back to its regular location.
However you do it, plan on strictly following this schedule until about mid-November.The Flower Set
If you've done your job right, you should see flower bracts forming in the fall and growing rapidly. Once the bracts have set and are growing, you can discontinue the dark/light cycle and treat as you would any other poinsettia.
This pattern—rest, active growth, dark/light—can be followed for many years with the same plant, and if it's done correctly, it will continuously yield holiday color.