Dried or fresh, raw or cooked, onions are an indispensable ingredient in a variety of soups, salads, breads, and casseroles. Onions are easier to grow than you might think, and they're a great plant for tucking into spare corners and along the edges of garden beds.
Onions come in a wide variety of shapes, sizes, and colors. The white, yellow, or red bulbs range in size from small pickling onions to large Spanish cultivars; they can be globe, top, or spindle shaped.
Most onions can be pulled young as green onions called scallions, but there is also a perennial bunching type, Allium fistulosum, that produces superior scallions and is practically disease and insect proof. Each bulb of the multiplier or potato onion (A. cepa Aggregatum group) multiplies into a bulb cluster, so with every harvest, you'll have bulbs to replant for a continual supply.
The Egyptian or top onion (A. cepa Proliferum group) produces a bulb cluster at the end of a long stem with a second cluster frequently forming on top of the first. It also has an underground bulb, which is often too pungent to eat. Other tasty plants include chives (A. schoenoprasum), garlic chives (A. tuberosum), and shallots (A. cepa Aggregatum group). For information on other onion relatives, see Garlic.
You can grow onions from transplants, sets, or seeds. Transplants, which are seedlings started in the current growing season and sold in bunches, are available from nurseries and by mail order. They usually form good bulbs over a short period of time (65 days or less), but they are subject to diseases. Choice of cultivars is somewhat limited.
Sets are immature bulbs grown the previous year and offer the most limited cultivar choices. They are the easiest to plant, the earliest to harvest, and the least susceptible to diseases. They are, however, more prone to bolting (sending up a flower stalk prematurely) than are seedlings or transplants.
If you plant onion sets, the sets may be identified only as white, red, or yellow, rather than by variety name. Most growers prefer white sets for green onions. When buying sets, look for 1/2-inch-diameter bulbs, because they're the least likely to bolt.
Growing onions from seed offers the great advantage of a wide choice in cultivars. The challenge with starting from seeds is that your crop will take up to 4 months to mature—gardeners in cold-winter areas will need to start their onion seedlings indoors.