Year in and year out, Americans buy more poinsettias than any other type of flowering indoor potted plant. Last year, for example, 36.1 million pots of poinsettias with a wholesale value of $146.1 million were sold in the United States, according to the USDA Floriculture Crops 2010 Summary.
Sales of spring flowering bulbs were a distant second at 22.5 million pots with a wholesale value of $59.8 million, according to the same report. Orchids were third in pots sold at 21.1 million, but, interestingly, had the highest wholesale value, $170.1 million. No other indoor flowering plant — Easter Lillies, African violets, florist chrysanthemums, azaleas or roses — came close to poinsettias in either number of pots sold or value.
After the holidays, what are homeowners to do with all of those poinsettias? Many will throw them away. However, with proper care, in frost-free areas or as house plants elsewhere. Here is a guide to keeping your poinsettia fresh during the holidays and to reblooming it next Christmas.
During the holidays and winter
Place the plant in a sunny room but avoid areas with cold drafts or excessive heat. When the soil is dry to the touch, take the plant to the kitchen sink, remove any decorative wraps and water it until the water drains through the bottom of the pot. Do not let the plant sit in water and do not fertilize it while it is in flower.
In the spring
In March or April, cut the plant back to about eight inches high. Water regularly, keeping the soil moist but not soggy. Fertilize once a month with a balanced, all-purpose fertilizer. By the end of May, the plant should be growing vigorously. Be aware that in its native habitat of Mexico and Central America the poinsettia (Euphorbia pulcherrima) can grow as large as a small tree, up to 16 feet tall.
In the summer
In early June, re-pot your plant in a larger pot, but make sure the new pot is no more than four inches wider than the original pot. Use a potting mix high in organic matter, such as peat moss. In frost-free zones, it can be transplanted into the garden. Best results will be obtained in a bed rich in organic matter that has good drainage and receives strong sunlight.
For potted plants, place outdoors in a bright location after all danger of frost has passed and nighttime lows are 55 degrees Fahrenheit or higher. Continue watering regularly, keeping the soil moist but not soggy. Increase the frequency of fertilizing to every two-three weeks.
Frequent pruning will be required to keep the plant bushy and compact. Each time a new shoot gets four-five inches long, just pinch off the growing tip. Pinching forces the plant to branch, creating the bushy look it had when you bought it. Do not pinch off any growths after Sept. 1.
In the fall
This is the most critical period. Decreasing hours of daylight and increasing nighttime hours cause poinsettias to set buds that produce flowers. (Note: What look like brightly colored flowers are really leaves. The flowers are the yellow buds within the colored leaves.) Starting Oct. 1 and continuing for about eight to 10 weeks leading up to the holidays, plants must have complete darkness for 14 hours every night. It's this long period of darkness that causes the leaves to change colors. Homeowners have tried a variety of ingenious ways to accomplish this — from putting them in a closet to covering them with a box. Use whatever "trick" works for you. But, be aware that any stray light from a street or household lamp or other source could delay or stop the color-changing process.
At the end of the 14 hours of darkness, give the plants six to eight hours of strong sunlight. (This is what gives the leaves their bright color.) If your plan is to give the plants bright light by moving them outside, keep them indoors by a sunny window if the daytime high temperature will be below 60 degrees. Continue watering and fertilizing them as you did in the summer. If all goes well, you should have beautiful poinsettias just in time for the most festive season of the year.