Long after the Christmas tree has succumbed to the warmth of our winter homes, the poinsettia lives on. Its cheery show of color is a reminder of the winter holidays well into the new year. Some people may consider the poinsettia a disposable decoration that should be tossed away once the other holiday ornaments are packed back into their boxes, but if you’re a houseplant lover, why not keep the plant growing throughout the next year? Expand your horticultural endeavors and see if you can engineer a thriving, colorful set of blooms for next Christmas.

While some scientific tinkering does need to be undertaken to ensure the subsequent blooming of the poinsettia, caring for the plant throughout the year isn’t at all difficult. It’s pertinent to note that the poinsettia is native to Mexico: There it grows as a thick-stemmed shrub, reaching up to 10 feet in height. Knowing the native range of any plant will give you a few cultural clues. In the case of this holiday gem, its native semitropical range keys us in to the fact that it prefers both a moderate temperature and humidity.

The flower of the poinsettia is white or yellow and very small. The plant parts we’re most appreciative of are the bracts, those brilliant red, burgundy, white, cream, yellow, pink and peach “leaves” that top each plant. Some poinsettias have variegated bracts that are striped, marbled or spotted. Poinsettias, along with carnations and mums, are one of the most important floricultural crops grown in the United States today. Some statistics show that more poinsettias are sold in November and December than any other plant throughout the year.

Over the years, plant breeding programs have improved the size, foliage color, plant shape, and duration of bloom of poinsettias. With proper care we can encourage the color and form of the holiday plant deep into winter.

Be sure to attend to the moisture needs of your plant. Overwatering is the main cause of death among houseplants, and it can deal a blow to your poinsettia if you are not careful. Too much moisture – a continual waterlogging of the soil, in particular – can promote disease growth in the root zone. Be sure to remove or at least poke holes through the foil wrapping around the pot. The foil holds in excess water and the lack of drainage can cause waterlogging around the roots.

Try to gauge the amount of water your plant requires by irrigating it thoroughly and hefting the pot occasionally as it dries out. Become familiar with what the pot feels like fully irrigated and allow the roots to dry out a bit before each watering. This is not to say that the roots should become completely arid; they should be kept moist but not soaking-wet all the time.

The poinsettia is a heavy feeder, and while it is at its height of showiness, you should fertilize the plant at every watering. Prepare a fertilizer solution by mixing 1 tablespoon of 10-10-10 soluble houseplant fertilizer, to 1 quart of water. Use about 1 cup of the solution each time you irrigate.

Keep your poinsettia out of warm or cold drafts: don’t place your festive plant near the cold-air return or a heating duct of your furnace, and avoid placing it by a drafty window or door. Avoid letting the bracts touch windowpanes, since freezing outdoor temperatures can cause damage known as edema. (You may have noticed this sort of damage on your other windowsill dwelling houseplants: darkened raised lesions on leaves caused by localized freezing temperatures that have resulted in the rupturing of cells.)

Maintain a room temperature from 65 to 70 degrees F for ideal poinsettia growth. Temperatures in excess of 75 degrees F will cause a decline in plant vigor. When the colorful bracts fade in late winter, cut back the stems to about 8 inches high and ease up on the watering.

Allow the root mass to dry out between waterings, but avoid allowing the soil to become so dry that the stems shrivel.

This procedure will allow your plant to slip into a semidormant state.

When new growth begins to emerge over the next six to eight weeks, return to normal watering and fertilizing regimes.

To encourage a repeat of blooms for the holidays of 2001, you’ll need to alter the growing environment of your poinsettia, starting in mid-September. By manipulating the length of time the plant is exposed to light and darkness, you will trigger flowering in the holiday plant.

Provide 14 hours of darkness by placing the plant in a cool, dark room or closet each night. Alternatively cover you plant with a large box or black fabric.

Maintain nighttime temperatures between 65 and 70 degrees F for proper flower development.

Remove the plant from darkness each morning and expose it to six to eight hours of bright sunlight.

After approximately five weeks of this devotion, you should be rewarded with brilliant color for the holidays.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, RR1, Box 2120, Montville 04941, or e-mail them to dianagc@ctel.net. Selected questions will be answered in future columns. Include name, address and telephone number.