People who love onions (Allium cepa) may be used to weeping for joybut tears don't have to be part of the affair. Sweet onions contain little pyruvate, the chemical that causes tears and hot flavor. Unfortunately, these types don't keep as well as their stronger-tasting brethren, so choosing the right onion depends on your needs.
In addition to flavor and shelf life, onions vary in size, shape, and color. More important, different types form bulbs in response to varying day lengths. If you choose a type inappropriate for your area, it may go to seed before bulbing up, form small bulbs, or not form bulbs at all.
Short-day selections need 10 to 12 hours of daylight and are well adapted to most areas of the South. These tend to be sweet, but they are poor keepers. They typically begin to form bulbs in spring. Examples are 'Burgundy', 'Crystal White Wax', 'Granex 33' ('Vidalia'), 'Southern Belle', 'Georgia Sweet' (Yellow grapex), 'Texas Grano 502', 'Texas Grano 1015' ('1015 Supersweet'), and 'Yellow Bermuda'.
Intermediate-day onions, requiring 12 to 14 hours of daylight, also grow well in the South. They have a stronger flavor than short-day types and keep longer. Examples include 'Candy Hybrid', 'Stockton Sweet Red', and 'Super Star Hybrid'. They usually form bulbs in summer.
Long-day onions, which need 14 to 16 hours of sunlight, keep the best. They form bulbs in summer. They're suited only to the Upper South and parts north. Examples include 'Ebenezer', 'Sweet Spanish', 'Walla Walla', and 'Yellow Globe'.
Bunching onions do not form large bulbs but have slightly swollen white stalks. Depending on where you're from, you may know them as green onions, scallions, or spring onions. They can be planted in fall or spring. 'Evergreen White Bunching' is a favorite selection. Egyptian walking onion (A. cepa proliferum) gets its name from the bulbils that cluster near the tops of the leaves; the foliage bends to the ground, and the bulbils take root. Shallots and potato onions (A. cepa aggregatum) are smaller, milder-flavored regular onions; see Shallots.
Cipollini onions are very small bulbing onions that are listed as in their own class in catalogs. They are flattish, 2- to 3 inches-diameter, sweet, long-day onions that come in red, yellow, or white.
You can grow onions from seeds, sets (small bulbs), or transplants. Sets and transplants are quicker and easier for beginners; starting from seed gives a larger crop for a smaller investment and offers a wider choice of selections.
In the Lower, Coastal, and Tropical South, onions grow well from seeds sown in fall. Sets and transplants can be planted from late fall throughout the winter. In the Upper and Middle South, sow seeds outdoors six to eight weeks before the last frost in spring; plant sets and transplants four weeks before the last frost.
Soil should be loose, fertile, and well drained. Space sets and transplants 45 inches apart (closer if you want to harvest some early as green onions). When planting sets, push them just under the soil surface, so the point of the bulb remains visible; when planting transplants, trim foliage back by about half after planting. Sow seeds 14 inches deep in rows spaced 1518 inches apart. Thin seedlings to 45 inches apart; thinnings can be eaten as green onions or transplanted.
To produce large bulbs, onions need moist soil and repeated applications of fertilizer. Scratch in 14 cup of 10-10-10 fertilizer per 10 feet of row before planting. Sprinkle this same amount around plants four to six weeks later and again when bulbs begin to form; water it inches Carefully eliminate weeds, being sure you don't damage the onion bulbs or their shallow roots. When most of the tops have begun to yellow and fall over, dig the bulbs, leaving the tops on; spread them out (tops and all) in a dry, dark place for 10 to 14 days to cure. When tops and necks are completely dry, pull off the tops and brush dirt from the bulbs. Store in a dark, cool, airy place; use mesh or cloth bags, not plastic ones.