The poinsettia you brought home from the garden center or grocery store could be your first step toward sustainability. In other words, consider keeping the plant around for a while instead of tossing it in the trash once the tree is down. A poinsettias planted outdoors when warm weather stabilizes can turn into the prettiest tropical plant in your yard. Even if it doesn't bloom again next Christmas, you can still enjoy it for many months. Here's what you should do for your poinsettia now and through 2011:
Taking care of it now
Avoid exposing the poinsettia to freezing conditions. Do not leave it in the car while you finish shopping. Take it home and place it inside the house as soon as possible after purchasing it.
§ Place your poinsettia in a spot with bright natural light, but do not expose it to direct sunlight.
§ Do not place your poinsettia in an area where it will be exposed to drafts, heat from appliances, radiators, or ventilation ducts.
§ The color of your poinsettia will last longer with temperatures around 65 degrees Fahrenheit during the day and 60-65 degrees at night.
§ The soil should be kept moderately moist; check every few days and water when the soil feels dry to the touch. Before watering, remove the pot covers or foil wrapping; water to saturate the soil, and then allow the pot to drain. Do not let the plant sit in standing water.
To rebloom it
Once the holidays are over, January through March, continue to care for your poinsettia as you did when you first brought it home. Allow the surface of the soil to dry between waterings, and be sure to apply enough water so that the pot is evenly moist and some drains out the bottom. Do not let it sit in water. Keep the plant near a brightly lit window, in a room where the day temperatures are between 65 and 75 degrees. Night temperatures can be cooler, but make sure your poinsettia doesn't get colder than 55 degrees. April 1st, cut the poinsettia stems back to about 8 inches, and don't worry if you don't have many leaves left after you cut it back — more leaves will sprout along the stems. Continue watering as before, but keep in mind you will most likely be watering less since you removed a lot of foliage. As soon as new growth appears, begin fertilizing once a week with a well balanced, all-purpose fertilizer. This is also a good time to replant your poinsettia into a larger pot. If the container is too large, the soil can hold too much water, causing the roots of the poinsettia to rot, so it's best to choose a new container that is no more than 4" larger than the original. You can also move your poinsettia outside for the summer months. Around mid-July, pinch each stem back, leaving three to four leaves on each stem. This makes your poinsettia nicely branched and bushy, and also creates lots of blooms. If you moved your plant outside, bring it back inside around the middle of August, and continue to water and fertilize through the rest of summer and early fall.
The tricky part
Poinsettias are short-day plants, meaning they naturally flower when the day length is less than 12 hours. Starting Oct. 1st, poinsettias need 14 hours of complete darkness daily, 6 p.m. to 8 a.m.. Cover the plant with a cardboard box, or place the plant in a closet or cabinet or even garage. No light, not even coming in under a closet door or opening the door, can happen. The dark treatment must be done every day from Oct. 1st until Thanksgiving. At the end of the dark treatment, the bracts (modified leaves that turn the showy colors we think of as poinsettia "flowers") start to change colors. Stop fertilizing at this time, and continue to care for your poinsettia the same as when you first purchased it.