If you have kept your poinsettia from last Christmas and want it to bloom for the holidays this year, start preparing it now.

Before the first frost, bring the plant indoors to a sunny room. It needs good light during the day, preferably direct sunlight. Keep a night temperature of 60 degrees, and warmer during the day.

Beginning this week, poinsettias need complete darkness every day from about 5 p.m. to 8 a.m. Put the plant in an unused cool closet, or put a cardboard box over it, to provide this long night. Flowering will be delayed if the plant is exposed to even a few seconds of light.

During the daytime, give it sunlight. Continue this routine until the flowers begin to show color late in November. It usually takes nine to 10 weeks to develop the red "flowers," which are really bracts, or specialized leaves.

Correct watering is important. Usually watering once a day is about right. Add enough water so that some trickles out the bottom of the pot. Then let it drain about 15 minutes, and pour off drainage water. The amount of watering will depend upon whether the plant is in a clay or a plastic pot. Clay dries out faster than plastic.

The Christmas cactus fails to bloom for many indoor gardeners. Generally this is because it does not get the long night treatment it needs to produce flower buds.

Under ordinary household conditions the plant will bloom during the Christmas season if it gets no light from sundown to sunrise, starting in October.

Place the plant in an unused cool closet or cover it with a box or black cloth so that it gets no illumination at all from about 5 p.m. to 8 a.m. for six weeks. During this time buds will form. Flowering occurs about nine weeks after the start of the treatment.

Temperatures, as well as day length, influences the blossoming of the Christmas cactus. The plant can be left outdoors as long as temperatures remain above 55 degrees. In an unlighted garden area, the nights are just long enough in the next few weeks to serve as part of the "long-night" treatment.

When you bring the plant indoors, keep it in a cool place, even in the daytime. Water when the top-soil begins to feel dry.