If you got roses for Christmas, you can make them last longer. They'll need food, water and cool temperatures to stay beautiful.

Lack of water is often the main reason for a short life. Even when roses are standing in a vase of water, stems may be unable to absorb moisture: bacteria or air bubbles in the stems prevent movement of water upward.

To remove this block, cut a half-inch off the end of the stem.Make the cut with the stem in water, using a sharp knife or pruning shears. A dull cut will mash the stem and close some of the tubules needed to absorb and transport water.

Occasionally a rose may wilt at or just below the bud or develop a weak stem. Recut it an inch from the base of the stem -- do this underwater, of course -- them submerge the entire bloom, stem and foliage, in tepid (100 degrees F.) water for 20 minutes. Usually the flower revives nicely; straighten the angle of the head or it will retain its bent neck.

A floral preservative provides food and eliminates bacteria which may clog the steps. Either Sprite or 7-Up can do the trick, research at the University of Michigan has shown. Mix one part water with one part soft drink and add a half-teaspoon of chlorine bleach to each quart of the solution. The bleach cuts bacterial growth; the sugar in the soft drink sustains life.

High temperatures cause rapid respiration, speeding up the life processes of cut flowers and shortening life. Respiration for roses is essentially stopped at 32 degrees, and increases rapidly as the temperature increases.To slow down growth activities keep the flower or plant as cool as possible.

After the roses have peaked but before they turn brown, preserve their essence. Remove the petals and let them dry for several days on a cookie sheet or some other flat surface. For each quart of petals add one tablespoon of fixative -- dried lavender and oak moss. Put the petals and fixative in a glass container and add two or three drops of your favorite perfume. Close the container, shake well, and shake again every other day for 10 days. For additional aroma, add a cinnamon stick and two to four vanilla beans. The peel of one lemon, dried and grated, will help to preserve it and add additional scent. Q: We bought a Norfolk Island pine and are using it as a Christmas tree. What does it need? A: The Norfolk Island pine (Araucaria heterophylia) is indeed a beautiful plant with its lacy foliage. It grows well as a house plant, needs to be moist in summer, somewhat dry in winter. Preferred temperatures are 60 to 65 degrees F. during the day, 50 to 55 at night. It shouldn't need repotting for three or four years. It requires good light but not direct sunlight. During the summer, put it outdoors in a shady place and fertilize it lightly once a month. Captain John Cook discovered this plant on Norfolk Island during his voyage around the world. Q: How can I get rid of spider mites on my house plants? A: Spider mites thrive on plants in the warm, dry environment of the home during the winter months. They construct an extensive system of webbing and multiply rapidly. There's a safe method of control that works fairly well. Put the plants in the bathtub and spray the foliage with lukewarm water under pressure. The pressure of the water knocks the mites off the leaves. Repeat once or twice a week for a month. Q: I have a miniature orange tree about 15 inches tall, in a five-inch pot. Does it need a larger pot? A: Probably. Turn the plant upside down, tap the rim of the pot on the table to loosen the ball of soil. Let it slide out instead of pulling it out with your hands. If roots can be seen and are matted together and crowded, the plant needs repotting. Q: I want to get some house plants and am afraid I cannot give them enough light. Are there some that need less than others? A: Light duration is as important as light intensity, since the total amount received is the product of both. Low intensity can be compensated by longer exposure -- two to 14 hours a day of artificial light, preferably fluorescent. Some plants with low light requirements: Chinese evergreen, cast-iron plants, bamboo palm, parlor plam, jade plant, English ivy, tricolor bromeliad and snakeplant. Q: My philodendrons on the windowsill refuse to grow upright; they bend as if to see what's happening out in the street. Why? A: When a house plant is near a window, the stem of the plant bends toward the light. A growth hormone increases in concentration more on the dark side than on the light side. The cells on the dark side grow more than on the light side. If a plant is turned halfway each day the stem usually grows upright. If left in one position for a week or longer it usually grows crooked. Q: Why can't I grow mums as large as those sold by the florist? A: When growing mums, removal of all but one flower bud per stem is necessary to get the high quality single bloom to develop. The small buds should be cut off close to the stem when they are no longer than a small pea. The disbudding must be done everyweek until the flowers are produced. The leaf growth should not be disturbed.