Onions have been used since prehistoric times. They continue to play an essential role in cuisines around the world. Like asparagus and garlic, onions are a member of the lily family. They are used as both a seasoning and as a vegetable.

There are two types of onions: green and dry.

Green onions, or scallions, are onions that are harvested when immature. They are long and finger-thin with white bases and green tops, both of which are edible. They are sold in bunches. Green onions are easy to grow in a home garden. If you plant them every few weeks, you will have a constant supply during the entire growing season. All other onions are classified as dry onions, meaning that they are harvested when mature and then allowed to dry until their skins are papery. This group includes: Bermuda, globe, pearl, red, Spanish, Vidalia, Maui and Walla Walla.

Bermuda onions are mild-flavored onions with an oval shape and white skin that has subtle vertical green stripes. They are sweet during the peak of the season (early fall), when they are good raw, but become stronger when stored.

Globe onions (also called yellow onions) are the most common of the dry onions. They are round and small or medium in size with yellowish-gold skins and a strong flavor. Use them for cooking. Globe onions are generally more economical and they keep for some time.

Pearl onions are tiny white onions with a mild flavor. They are usually cooked whole; they make good additions to stews. Pearl onions are also pickled.

Red onions (also called Italian onions) may be round, oval or slightly flat. They are covered with a dark red to purple skin. When cut, their rings of whitish flesh are outlined in purple. Red onions are generally sweet unless they have been stored for a long time.

Spanish onions are large and round with a caramel-colored skin. These are fairly sweet and can be eaten raw.

Vidalia, Maui and Walla Walla are all very sweet onions. They have taken their names from the areas where they grow: Vidalia, Georgia; Maui, Hawaii; and Walla Walla, Washington. Vidalia are generally the sweetest.

Green onions are available all year. They are most abundant in the spring and summer. Bermuda, Spanish and red onions are available all year but they are sweeter in the late summer and early fall. Sweet onion varieties have short seasons: Maui from April to July, Vidalia from May to June, Walla Walla from June to September.

Green onions should have firm white bottoms and crisp green tops. Dry onions should feel heavy for their size, dry and firm to the touch with no soft spots or sprouts. Onions should smell mild when purchased. Avoid excess dirt or dark spots as this may indicate that mold is present.

1 pound onions = 3 large or 4 medium onions; 2 to 3 cups chopped.

1 green onion = 1 or 2 tablespoons sliced or chopped.

Store green onions in the refrigerator in a plastic bag for up to five days. All other onions should be stored in a cool, dry area with good air circulation for up to two months. Sweet onions may not store for quite as long. Check them periodically and discard any soft onions.

To prepare green onions, wash them thoroughly and trim off the roots. Remove any wilted or discolored layers. Green onions may be sliced, chopped, cut into lengths or used whole. The green tops can be cooked, but they cook more quickly than the white bases.

To peel dry onions, slice off the stem and root ends, make a shallow lengthwise slit through the papery skin and remove the outer layer of the onion. To peel pearl onions, drop them into boiling water for about two minutes. Drain the onions and plunge them into cold water to stop the cooking. Cut off the stem end. Squeeze the onions between your thumb and forefinger to separate them from the skins.

To slice dry onions, peel the skin. Cut in half through the root end with a utility knife. Place the onion half, cut side down, on a cutting board. Cut into thin vertical slices. Onions may also be cut crosswise into slices. The slices may be separated into rings. To chop onions, place the cut side down on a cutting board. Cut the onion into slices perpendicular to the root end, holding the onion with your fingers to keep it together. Turn the onion half and cut it crosswise. Repeat with the remaining half.

When onions are cut, they release sulfur compounds that bring tears to the eyes. Try one of these suggestions for minimizing tears:

• Wear glasses or goggles.
• Place the onion in the freezer for 20 minutes before chopping.
• Chew a piece of bread while peeling and chopping.
• Chop onions with your mouth closed.
• Work under an exhaust fan.
• Work as quickly as possible, never touching your eyes.
• Wash your hands, knife and cutting surfaces when finished and store cut onion in a resealable plastic bag until you need them.