It isn't Christmas without a poinsettia in the house, as well as such other holiday favorites as Christmas cactus, kalanchoe and amaryllis.

Poinsettias are the top-selling potted flowering plant in the United States. More than 75 million poinsettias are sold in the six weeks before Christmas. With a little TLC, they will remain beautiful for months.

There is a widespread belief that poinsettias are poisonous. It is a myth. Ohio State University, in cooperation with the Society of American Florists, conducted studies demonstrating the safety of poinsettias. They concluded that no toxicity was evident at experimental ingestion levels far exceeding those likely to occur in a home environment.

In fact, the Poisindex, the primary information resource used by most poison control centers, shows that a 50-pound child needs to ingest more than 500 poinsettia bracts to exhibit any signs of poisoning.

Poinsettia belongs to the genus euphorbia. Its relatives include crown of thorns, pencil tree and gopher plant. All are succulents with a milky sap that can cause skin irritation.

The plants are available in all sorts of colors and forms. But regardless of the variety, they're all tropical plants native to Central America, so they like warm temperatures.

When selecting a poinsettia:

1. Choose one with healthy leaves. Pass up those with yellowing leaves or brown leaf tips.

2. Look for one with brightly colored bracts. Faded color means it's past its prime.

3. Forget plants producing pollen (yellow dust) from small flowers in the center of bracts.

Here are tips for prolonging its life in your home:

1. Read the care tag that comes with the potted plants.

2. Put a covering over the plant while transporting it home to avoid leaves dropping.

3. Poke holes in the bottom of the decorative foil wrap to enable drainage.

4. Place poinsettias in a bright location, preferably an east-facing window, for at least four hours. Keep it back from your southwest windows, because they heat up during the day.

5. Poinsettias are mostly trouble-proof if you keep the soil evenly moist, but not wet. Waterlogged soil causes leaves to fall.

6. Let soil dry slightly between waterings.

Try growing your potted poinsettia outside. For it to bloom again next Christmas, follow these tips:

1. In March, heavily prune it back to a foot high.

2. Plant in the garden where it receives morning sun and afternoon shade.

3. Occasionally pinch the new shoots to thicken the plant.

4. Fertilize twice monthly, starting in April, with Miracle-Gro, Peters or Shultz.

5. In October, cover the poinsettia with a cardboard box for 15 hours (from 5 p.m. to 8 a.m.) each night until the colored bracts (modified leaves) form. If you interrupt the dark period for a short time with light from a window, streetlight or any other light, it will delay flowering or the plant may not flower at all.

6. Finally, remember to protect poinsettias from late fall and early winter chills by covering them when temperatures approach freezing.

7. Or you can forget about it and it will still bloom again, but after the festive season.

Christmas cactus: Thanksgiving and Easter cactuses are part of the same family. These are true cactuses but they are from mountain regions of Brazil. Red, pink, lavender or white flowers burst forth from the ends of cascading stems that are uniquely broad and flattened. To care for them:

1. As they approach the festive season, keep the plants in a cool spot (50 degrees) at night.

2. During the day, place them in a bright location, but away from direct sunlight.

3. Keep the soil evenly moist but not wet.

4. Fertilize every two weeks as is done with poinsettias.

Kalanchoe: They have beautiful star-shaped flowers in clusters covering the plant. The leaves are succulent and dark green. They have red or pink flowers and sometimes coral or yellow blooms. Care tips include:

1. With their thick succulent leaves, they won't need much water.

2. Let the soil become nearly dry between waterings.

3. Shiny leaves turning a dull green signal it's time to water again.

4. They like bright light indoors.

5. At night, put them where it stays about 60 degrees.

6. You can reflower them by following the techniques to rebloom poinsettias.

Amaryllis: These are magnificent flowering bulbs, which bear trumpet blooms in a wide range of holiday colors. You'll find them in florist shops and garden centers in bloom or potted and about ready to bloom. To care for them:

1. Keep them warm, in a sunny location while leaves and flower stalks grow.

2. As soon as the buds develop, move them to a spot where they get indirect light.

3. Water them regularly, because they are thirsty plants.

4. Heat shortens the bloom life, so move blooming amaryllis to a cool location at night.

When they are finished blooming, here are tips for new flowers next year.

1. As flowers fade, cut off the bloom spike but not the leaves.

2. Apply a fertilizer, as mentioned above, every two weeks for the next six months.

3. At that time, the plant goes dormant and leaves turn yellow, so place it in a cool, dark place and don't water it until November.

Or, after the frosty season is over, plant your amaryllis around your home. During the summer, it will amaze you with the number of blooms that will come from that mammoth bulb. One woman collected throwaway bulbs and had dazzling color all season long.

Finally, keep all potted flowering plants away from ripening fruit! Ethylene gases given off by fruits cause flowers to prematurely fade.

Linn Mills writes a gardening column each Thursday. You can reach him at linn.mills@lvspringspreserve.org or at the Gardens at the Springs Preserve at 822-8325.