Poinsettias are native Mexican plants which have come a long way since they were introduced to the United States in 1825 by Joel Roberts Poinsettia, a botanist and the first U.S. ambassador to Mexico. Mr. Poinsettia was a southern plantation owner who, while visiting Mexico, was impressed with this brilliant red flower he found blooming during December. He had some plants sent to his home in Greenville, South Carolina. They did well in his greenhouse and he gave lots of specimens to his many friends.

In 1920, Paul Ecke Sr. developed the first poinsettia variety that could be grown as an indoor potted plant and he eventually introduced it to flower growers across the country. Most of the original varieties were red while, pink, white, yellow and verigated types now appear on the market.

Today they are the traditional American Christmas flower, displayed widely during the holidays. No longer sold just by florists, poinsettias can be found at dime, drug, discount and even convenience stores. Most are red, by far the most popular color, but a few are pink or white.

Besides being pretty, poinsettias are big business. Millions of poinsettias grace the festive scene during the Christmas season. It's an American tradition. In North Carolina, Dr. Joseph Love, extension horticultural specialist with NCSU was instrumental in the development of the poinsettia industry in this state. Now, more than a dozen area nurseries are growing thousands of plants for the holidays. One local nursery, for instance, started by growing 1,000 poinsettias l0 years ago and has added another l,000 plants each year to meet the demand.

Several years ago poinsettias often were thrown out with the Christmas tree. If the plants lived through the holidays, people were pleased. With the old varieties available, there was no chance of carrying poinsettias over to rebloom. But the varieties grown today can last indefinitely with proper care. With a bit of luck you can even propagate your own and have free Christmas gifts for your friends next December. It is possible to use the Christmas flower as a green outdoor plant during the summer, then encourage it to rebloom the next holiday season. The following are hints for those who received poinsettias for presents this Yuletide:

•Place the plant in sunny location, but avoid temperature fluctuations and drafts. Keep the plant away from cold windows, radiators or air registers. Water the plant whenever the soil looks and feels dry, keeping it evenly moist.

•If the plant comes in holiday foil, punch a hole in the bottom for drainage. Fill the pot to the top with water and allow it to soak into the soil. Repeat until water begins to trickle out of the base hole of the pot showing that the soil is wet to the bottom. Discard all excess water.

•As the flowers pass maturity, leaves and bracts will fall. Remember, their bright colored "flower petals" aren't really petals at all. They're leaves that have reddened and are called "bracts." When about half of them have fallen off, gradually reduce the amount of water you give the plant until the soil is completely dry. The plant is now in a state of dormancy and can be stored in the basement or a dark room without watering.

•In the spring start watering again. Use a soluble complete fertilizer about twice a month. Cut stems back to four to six inches and repot the plant in new soil. When danger of late spring frosts has passed, put the poinsettia pot into the ground in your garden. Select a place that receives full sunlight most of the day. Fill in with garden soil to the top of the pot. Turn the poinsettia pot a quarter turn each week. Pinch the terminal shoots to encourage branching. Remove a half inch of the terminal shoot by hand or with a sharp knife every four to five weeks. Continue pruning until mid August.

The poinsettia can be propagated by taking cuttings from July 15 to Sept. 1. Root cuttings in a mixture of equal parts of peat moss and perlite. Sprinkle cuttings frequently on bright days to prevent drying. If you are rooting cuttings outdoors, some shade on bright days is necessary to avoid excessive water loss. More cuttings may be taken when further growth has occurred on the stock plant. After four to six weeks transfer cuttings into six inch pots with three poinsettia plants in each pot.

About the middle of September bring the plant into a sunny place indoors. But here is the secret to achieving blooms: your poinsettia must be kept completely dark from 5 p.m. to 8 a.m. This can be accomplished by placing a large cardboard box over the plants or by placing them in a dark closet during these hours from the end of September to Thanksgiving. The dark period must not be interrupted by even small amounts of light since flowering will be delayed or prevented.

Carl Matyac, Ph.D., is an agriculture extension agent with the Orange County Cooperative Extension office. Contact him at 245-2062 or at carl_matyac@ncsu.edu