The poinsettia is one of the most spectacular symbols of our Christmas celebration. In recent years, production of poinsettias has undergone changes that have resulted in a much longer lasting plant. Scientists have developed plants of horter stature and "blooms" in shades of red, pink, white and marbled, which last as late into the new year as February or March.

Here are some hints for prolonging the life of your poinsettia.

Water thoroughly when you receive it. If the pot is wrapped in foil, puncture the foil so the water will drain out of the pot. Discard any drainage water. Thereafter water every three or four days.

Remember that a poinsettia must have at least six hours of bright indirect light daily.

Place the plant where it will not be subjected to cold drafts or hot air from radiators or ventilating ducts.

The brilliant color will be prolonged if it is kept in a cool location, preferably where temperatures do not exceed 70 degrees in the daytime; 60 degrees at night is suitable.

Forist's azalea will remain in bloom for several months if given diffused sunlight and a temerature of 55 to 60 degrees. It will require large amounts of water and frequent misting. Remove the flowers as they fade.

If you receive an amaryllis in flower, place it in full sun or in the brightest light possible and keep the soil moist. Turn the pot every day or so to keep the flower stalk erect. The blossom will last longer if the room is cool-65 to 70 degrees in the daytime.

The ornamental pepper and Jerusalem cherry are annual plants. New plants can be started from the seed of the dried fruit. The peppers are edible; the cherries are not. Give them plenty of water and direct sunlight. Low humidity can cause plants to drop leaves.

Norfolk Island Pine is a fine, small potted Christmas tree that adapts very well to holiday decorative use.

If you don't already own a Norfolk Island Pine, the Christmas season is a good time to acquire this handsome houseplant. When you buy, select a plant that has a straight trunk, preferably with a stake if it is a small tree, to assure that it will grow erect.

Trim the delicate flexible branches with lightweight ornaments such as ribbon bows, and spunglass or blown glass angels and baubles. Use miniature light bulbs on a strand of fine wire carefully draped over branches. Heat from these small bulbs will not damage the plant in the brief time they are used.

After Christmas, place the tree where it will get good light, such as an unobstructed north window, or a south window during the winter. Turn it regularly to prevent unbalanced growth as it will tend to lean toward the source of light. Keep the soil evenly moist and the air temperature not higher than 70 degrees.

In the summertime, the tree can be put outdoors in light shade or on the patio or porch. Indoors, move it away from a sunny window to a cool bright location.

Norfolk Island Pine is a slow grower and probably will not require repotting for two or three years. Feed it every six months with a general houseplant fertilizer.

Your Norfolk Island Pine can become part of your own Christmas tradition and still be a satisfying houseplant the rest of the year.

Container-grown evergreen Christms trees are not houseplants. Landscape architects and horticultural specialists agree it is not a good idea to buy a living Christmas tree for in most cases the survival rate is low. The decorative indoor use of a living tree puts it under such stress that it can't be expected to recoer and grow, even when special precautions are taken before bringing it indoors and after it is replanted outdoors. It is an expensive venture and a lot of ifs are involved.