Nothing you can grow on your windowsill in the winter can be more spectacular than an amaryllis. The breathtaking flowers of dinnerplate size can be brought into bloom any time from Christmas until Easter. It is easy to grow, and right now you can shop your garden center or mail order seed catalog for bulbs for Easter blooms of white, pink or candy stripe.

If you think the bulb is expensive, consider it an investment, for even in an apartment you can count on its blooming a second and third year if you take care of it. Bulbs can be bought individually preplanted in plastic pots and all you have to do is water and watch them grow. Or you can buy a bulb and plant it yourself.

If you plant the amaryllis bulb yourself, use a pot about 6 inches in diameter - an inch or two wider than the widest part of the bulb. I use clay pots because their weight is a counter-balance to the tall, heavy bloom stalks. Place pebbles or broken pot pieces in the bottom of the pot to provide good drainage. A gritty potting soil is best: the type usually sold for African violets is suitable. Plant the bulb so that two-thirds of it is exposed above the soil. Water it well and set in a warm, dark, airy place until growth starts.

When the tip of a leaf or flower bud appears and extends well above the neck of the bulb it is time to move the pot to a sunny place. Give it plenty of water. Once a week fertilize with a liquid houseplant fertilizer. In about four to six weeks the blossoms will appear - usually four to a stalk.

During this growing period, turn the pot frequently to keep the flower stem upright as it will tend to lean toward the light. A plant stake or similar support will keep te heavy head from toppling. Be careful not to damage the bulb when you insert a stake into the pot. Blossoms will last longer if the room is cool - 65 to 70 degrees.

A large bulb willproduce two and somtimes three flower stalks, one after another. When the first flowers have faded, cut them off but leave the stalk which, along with the leaves, will continue to nourish the bulb. Then watch for its successor! Remove the old flower stalk when it becomes an unsightly brown.

Some amaryllis bulbs flower before the leaves appear. When leaves do appear, keeping them healthy is important to the life of the plant. After the flowers are gone, keep it on a sunny windowsill and maintain it in active growth by watering and fertilizing about every three weeks. At this stage fish emulsion is especially good for amaryllis. Good summer-long care is essential for formation of buds within the bulb for next year's bloom.

Amaryllis can be summered outdoors on a balcony or in the garden as you do other houseplants. The bulb remains in the pot. In the garden, sink the pot in the earth in a lightly shaded place. Cinders or gravel in the bottom of the hole will help prevent invaion by venturesome earthworms. I think it is advisable to provide a support for the foliage at this time.

Before frost in autumn, bring the pot indoors, encourage th bulb to go dormant (rest) by gradyally withholding water. As the leaves yellow and wither, cut them off. Store the pot in a cool (50 degrees) dark place; water only enough to prevent the bulb's shrivelling. In three or four months, evidence of growth will let you know that it is time to move the pot again to your sunny windowsill and to resume watering and tertilizing. The bulb will not need to repotted; remove about an inch of soil from the pot and replace it with fresh mixture.

"It seems to be taken for granted that an amaryllis bulb ought to grow and bloom alone in a relatively small pot," wrote O. Hobart Mowrer, emeritus research professor, University of Illinois, in American Horticu lturist, late winter 1977. "If a plantlet appears it is supposed to be gently separated from the parent bulb and put in another pot" to bloom several years hence. Mowrer reports an accelerated blooming date through leaving plantlets undisturbed.

"Early in the summer of 1974, I noticed that a new plantlet had appeared alongside its 'mother' . . . I put them together in a slightly larger plastic pot . . . and by the end of the summer, the new bulb had become so large that it and the original one crowded the pot to such an extent that it was pushed into a decidedly oblong shape; so, again without disturbing the rootball, I transplanted the two bulbs to a 10-inch plastic pot - and both bulbs bloomed late that winter (1975). The following summer more new plantlets appeared, and one of them was strong enough to bloom along with the two older bulbs early in 1976 . . . with a nice accompanying growth of foliage."*