Onions are a standard in the home garden and a staple in the kitchen. Onions are actually members of the Amaryllidaceae or the lily family, which also includes leeks, garlic and shallots. Two basic types of onions exist: onions that produce one single bulb in a season and the cluster producing perennial types.
The Allium cepa is one of the most common types of onions grown in the home garden, according to the Ohio State University. This onion is started from plants, seed or sets as a dry bulb or spring onion. Usually home gardeners use onion sets to start plants which require around 100 days from planting to maturity for single bulb variety. If the goal is to produce spring onions it takes approximately 30 days from sets or 40 to 50 days from seed.
This type of onion is the cold hardiest variety of onions, according to the Alabama Cooperative Extension System. The taste is not as desirable as bulb onions or scallions, but is available during cooler months when other types are not in season. Bulbs are formed at the top of the plant. Egyptian onions do not form seeds and are started from sets.
A Bermuda onion is referred to as "sweet" onions and is the parent plant from which a number of different cultivars are derived. These varieties include the white or yellow Bermuda, Texas grano 1015 and 502 along with the Excel and Texas granex 33 or Vidalia onion. Sweet onions are generally fresh onions that are best eaten as soon as they are harvested.
This perennial, bulb-forming type of onion produces small sized bulbs in a cluster. Shallots are usually ready to harvest about three to four months after planting and are a cool weather onion. Mature bulbs only measure approximately 1 to 1 1/4 inches in diameter and are shaped similar to a pear.
Scallions are a type of spring onion producing clusters of small bulbs about the size of a pearl. This type is also known as a Japanese onion, bunching onion, Welsh onion or a multiplier onion. Plant in late winter or early spring to achieve a harvest in early summer if starting from seed. If an early spring harvest is the goal, then plant seeds in the fall or late winter.
Varieties of onions are also classified as long day, intermediate day and short day. The yellow and white granex, white Bermuda and 1015Y Texas SuperSweet are short day varieties. Intermediate day varieties include the Cimarron and the sweet red. Included in the long day varieties are the Spanish, Walla Walla and the first edition onions.