The edible lily: three tasty onions interest both gardeners and gourmets. Onion sets: use dime-size for bulb onions, larger ones for scallions

When Alexander the Great was spreading Greek influence around pretty much at will, one of the few things to stop him in his tracks was a lack of onions. At one stage his armies told him bluntly that they wouldn't take another step without them, such was the stock they placed in the humble vegetable. Apparently cooks, chefs, and homemakers have found this edible lily (it's a first cousin to the beautiful amaryllis) indispensable from ancient times right on down to today. And for good reason.

No other vegetable flavors a meal quite so effectively. Gardeners like it because it can be very productive for the space it occupies and is relatively easy to grow. You can even grow enough for a meal or two in a plant pot.

A majority of gardeners raise onions the easy way, by planting sets (small onion bulbs). But increasing numbers in recent years have begun to sow seeds. It may be time-consuming and require more effort, they say, but the choice of varieties is much greater.

This year there are some very interesting newcomers to add to the list: lime green and tearless, jumbo-sized with good storage qualities, and a variety that, even in the North, can be sown outdoors in summer and harvested late the following spring.

About a decade ago Ron Engle, then research director for Arco Seed Company, began breeding an onion that could overwinter in the Pacific Northwest. He worked with the Walla Walla sweet, Stockton Yellow Globe, and the Sensu Yellow Globe from Japan, looking for hardiness, early maturity, and resistance to early seed stalk formation.

Repeated crossings finally produced the sought-after onion. But Sweet Winter, as it is named (available from Parks Seeds, Greenville, S.C.), even exceeded the goals set for it. It can survive temperatures as low as 20 degrees below zero F., which makes winter-grown onions possible over much of the United States. Given some additional protection it can stand still lower temperatures.

Sow early enough (between Aug. 10 and Sept. 15 in most regions) so that the stem, or shank, is almost as thick as a pencil by the time growth stops in late fall. In tests, the flat, mild bulbs have reached 31/2 inches by mid-June and full, tops-down maturity a month later.

Plant in raised beds to avoid standing water. A mulch to prevent frequent freezing and thawing throughout the winter is also important.

The Lancastrian, or Football, onion (Thompson & Morgan, Jackson, N.J.) appears poised to break records. Bulbs of 5 pounds are quite readily attained with this strain, and it is considered one of the few breeds that could challenge the 7-pound, 6-ounce world record. It is a white, sweet onion that stores well, despite its size.

This breed was developed in Lancashire, in the north of England, and last year proved itself in US trials in Vermont, Oregon, and New Jersey. Just how well it would do in the South remains a question.

Gurney Seed & Nursery Company (Yankton, S.D.) promises ``no more tears'' with its new Lime Green onion. What the company means is that the volatile oils that escape when an onion is cut have been largely reduced without compromising the flavor. The onion's flesh is white and the top is lime green.

Onion seedlings are slow starters, so sow seeds indoors at least eight weeks before you plan to set them out. If you make your own soil starter blocks, try sowing each block with three or four seeds, and don't bother to thin after they germinate.

European growers who have long practiced this method harvest clusters of good-sized onions. Obviously, these clusters would be set out on wider spacings than you would with individual plants.

As a general rule, seedlings, or sets, are set out 4 inches apart in rows at least 12 inches apart. In wide rows or beds, try 6 inches apart in all directions.

Dutch Valley Growers, one of the nation's largest producers of onion sets, has put out a brochure on growing onions from sets. One of its recommendations says to plant sets just below the surface of the soil for mature cooking onions, or 2 to 3 inches deep and almost touching if you're looking for slender, white-stemmed scallions.

If all you have for a garden are a few flowerpots, grow scallions. You'll be harvesting them in about 4 to 5 weeks.

Onions are heavy feeders, so dig plenty of compost or aged manure into the top 4 inches of soil. Side-dress with more compost or fertilizer when they begin to bulb up. Keep the soil moist until the tops begin to fall over. A light mulch is beneficial.

The Dutch Valley onion bulletins should be available free from your garden center. Otherwise, write to Dutch Valley Growers, PO Box 304, South Holland, Ill. 60473.