Poinsettias aren't considered by most people to be a Valentine's Day flower. Improved strains of that traditional Christmas plant, however, allow an extended period of beauty, and some still look remarkably attractive.

Let's review the advice I gave you in December to extend the color show of this long-lasting semitropical plant.Place the pot in a well-lighted location where temperature fluctuations and drafts can be avoided. Direct sunlight will not harm the plant but may shorten the life of the flowers. Keep the plant from touching cold window panes to prevent bract or leaf discoloration.

Examine the plant regularly and add water when the soil surface feels dry to the touch. Frequency of watering will depend primarily on the temperature and humidity in your home. When watering, fill the pot to the top with water and allow it to soak in; water again and allow the excess to drain out the bottom. Discard this excess water.

Fertilize every seven to 10 days. Use a complete type of chemical fertilizer such as a 20-20-20 at about half the recommended strength or 1 teaspoon per gallon of water.

Lack of light and dry, undernourished soil are the main reasons leaves drop, and the plant should be discarded.

There are those of you who are reluctant to part with that living "family member" regardless of its appearance! You're waiting for information I promised you to preserve its life and give you hope of continual growth with this perennial plant to which you've become attached. It's relatively easy to keep it growing for another nine or 10 months but rather difficult to produce the bright red show of color for next December. Most poinsettia users prefer to buy new plants each year.

As the plants pass maturity, the leaves and bracts will fall. When most of the leaves have dropped, stop fertilizing and gradually reduce the amount of water being applied until the soil is nearly dry. The plant is then in a dormant state and can be stored until spring in a basement or dark room where the temperature will be around 50 degrees F. Water only occasionally to prevent stem shriveling.

Poinsettias, and many other seasonal blooming plants, can be maintained as house plants. Some varieties will retain most of their foliage through an entire year while at the same time making new shoot growth. Whatever the winter treatment, place the plant outside in the garden when the weather moderates and there is no danger of frost. Prune back to within 6 inches of the pot, repot in new soil, water, and feed to force new growth.

When the new shoots make 5 or 6 inches of growth, pinch out the growing tip, leaving at least two leaves below the pinch. As new shoots grow from the bases of the leaves and make 5 or 6 inches of growth, pinch out the growing tip of the newer shoots. Continue this practice until the middle of August to form a busy, compact plant.

During this time, whether the poinsettia is handled as a house plant or grown out of doors, fertilize the plant monthly to insure normal growth. Use a complete soluble fertilizer at the rate recommended by the manufacturer. If the plant is grown outside, dig a hole twice the size of the pot and line it with gravel to insure the pot does not stand in a puddle of water. Place the pot in the hole, and fill the hole with soil to the top of the pot. Grow in a garden area which will receive full sunlight. To ensure a balanced plant, give the pot a one-quarter turn each week.

Control snails and slugs with a commercial bait. If grasshoppers visit your garden, keep the poinsettia protected with sevin or malathion.

In late summer or early fall when the night temperatures drop below 55 to 60 degrees F, bring the plant inside and place it near a sunny window, away from drafts. Follow the poinsettia care instructions mentioned earlier.

The poinsettia is in the same day-length group as the chrysanthemum. This means that flowers begin to form when the days are shorter, or more accurately when the nights are longer. With the natural fall and winter day length the poinsettia normally blooms right after the first of the year. However, with lights inside the home, a poinsettia may not receive a long enough period of darkness to start the blooming process and could stay vegetative throughout the winter. To overcome this indoor light problem, place the poinsettia plant in a completely dark area from about 5 p.m. to 8 a.m. daily until red color starts to develop on the top leaves or "bracts." Interrupting the darkness by even a few minutes may cause failure of bloom. Bring the plant in ordinary light when the bracts begin to show color, although better results will be obtained if you wait until the bracts are almost fully expanded.

The following is a general time schedule for handling poinsettias:

Mid-September - Bring the plant inside and place in an area where drafts can be avoided and the temperature does not drop below 60 degrees F.

Early October - Begin giving the plant long nights (darkness from 5 p.m. to 8 a.m.) Cover with a dark plastic bag if the room is lighted during those hours.

Mid-November - Color should be showing in the bracts.

Early December - Bract color should be almost complete; plant can be brought into ordinary light.

During the "bloom" forcing period, keep the temperature between 60 and 70 degrees F. The plant should receive all possible sunlight during the day. Reduce fertilizer applications, since the plant will be making less growth while in the house. If possible, avoid spraying the plant with chemicals after the bracts begin to develop color.

You'll not have, most likely, the same quality of plant that came from the commercial florist or greenhouse. Although it's a lot of time and trouble, you can proudly say, "I did it myself."