Common name: onion

Botanical name: Allium cepa

Origin: Southwest Asia

Varieties

Soil and growing conditions affect the flavor of an onion as much as the variety.

Description

Onions are hardy biennial vegetables usually grown as annuals. They have hollow leaves, the bases of which enlarge to form a bulb. The flower stalk is also hollow, taller than the leaves, and topped with a cluster of white or lavender flowers. The bulbs vary in color from white through yellow to red. All varieties can be eaten as green onions, though spring onions, bunching onions,

scallions, and green onions are grown especially for their tops. Green onions take the least time to grow. Bermuda and Spanish onions are milder than American onions. American and Spanish onions generally take longer to mature than Bermuda onions.

Where and when to grow

Most onions are sensitive to day length. The American and Spanish onions need long days to produce their bulbs, and the Bermuda onion prefers short days. Onions are also sensitive to temperature, generally requiring cool weather to produce their tops and warm weather to produce their bulbs. They're frost hardy, and you can plant whichever variety you're using four weeks before your average date of last frost. In the South, onions can be planted in the fall or winter, depending on the variety.

How to plant

Onions are available in three forms - seeds, transplants, and sets. Sets are onions with a case of arrested development - their growth was stopped when they were quite small. The smaller the sets are, the better; any sets larger than the nail of your little finger are unlikely to produce good bulbs. Sets are the easiest to plant and the quickest to produce a green onion, but they are available in the least number of varieties, and are not the most reliable for bulb production - sometimes they'll shoot right on to the flowering stage without producing a bulb. Transplants are available in more varieties than sets and are usually more reliable about producing bulbs. Seeds are the least expensive and are available in the greatest variety, but they have disease problems that sets don't have and take such a long time to grow that the forces of nature often kill them before they produce anything. In limited space you can grow onions between other vegetables, such as tomatoes or cabbages, or tuck them in among flowers - they don't take much room. They can also be grown in containers. An eight-inch flowerpot can hold eight to 10 green onions. Onions appreciate a well made, well-worked bed with all the lumps removed to a depth of at least six inches. The soil should be fertile and rich in organic matter. Locate most bulbs in full sun - green onions can be placed in a partially shady spot. When you're preparing the soil, dig in a complete, well-balanced fertilizer at the rate of one pound per 100 square feet or 10 pounds per 1,000 square feet. When you plant transplants and sets, remember that large transplants and large sets (over three quarters inch in diameter) will often go directly to seed and should be grown only for green or pulling onions. Grow smaller transplants or sets for bulbs. Plant transplants or sets an inch to two inches deep, and two to three inches apart, in rows 12 to 18 inches apart. The final size of the onion will depend on how much growing space it has. The accompanying illustration shows how to plant onion transplants or sets. If you're planting onions from seed, plant

the seeds a quarter inch deep in rows 12 to 18 inches apart, and thin to one to two inches apart.

Fertilizing and watering

Fertilize before planting and again at midseason, at the same rate as the rest of the garden.  The soil should not be allowed to dry out until the plants have started to mature - at this stage the leaves start to get yellow and brown and to droop over. Then let the soil get as dry as possible.

Special handling

Onions are not good fighters; keep the weeds from crowding in and taking all their food and water. Keep the weeds cut off from the very beginning since they are hard to remove when they snuggle up to the onion. Thin conscientiously; in a crowded bed onions will mature when very small without growing a bulb.

Pests

Onion thrips and maggots are the pests to watch for. Discourage thrips by hosing them off the plants, or control them chemically with Malathion or Diazinon. Prevention is the best nonchemical control for maggots - put a three- or fourinch square of plastic around the plants to discourage flies from laying their eggs near the plants. To control maggots chemically, drench the soil around the plants with Diazinon at the first sign of damage.  

Diseases

In areas that produce onions commercially, onions are susceptible to bulb and root rots, smut, and downy mildew. Planting disease-resistant varieties when possible and maintaining the general cleanliness and health of your garden will help cut down the incidence of disease. If a plant does become infected, remove it before it can spread disease to healthy plants.

When and how to harvest

Harvest some leaves for flavoring throughout the season, and harvest the green onions when the bulb is full but not much larger in diameter than the leaves. Harvest dry onion bulbs after the leaves have dried. Lift them completely out of the soil; if the roots touch the soil they may start growing again and get soft and watery.

Storing and preserving

Store green onions in the refrigerator for up to one week. Let mature bulbs air-dry for about a week outside; then store them in a cold, dry place for up to six or seven months. Do not refrigerate mature onions. You can also freeze, dry, or pickle onions.  

Serving suggestions