There is little conclusive evidence as to the exact location and time onions were discovered, but many archaeologists, botanists, and food historians believe the vegetable originated in central Asia.
Dry onions (Allium cepa), a part of the Amaryllidaceae family along with chives, garlic, leeks, and shallots, may have been the earliest cultivated crop—as they were easy to grow, transportable, and less perishable than many other foods.
Types & Varieties
Highly adaptable, onions are grown successfully throughout much of North America. Dry onions refer to large, bulbous onions with a shiny, waxy outer layer of skin, sold in stores as yellow, red, or white.
Short-day varieties (often referred to as Bermuda/Grano/Granex) are typically grown in southern states where temperatures tend to be warmer all year round.
This includes the highly popular Vidalia sweet onions, grown exclusively in Georgia, which have a higher concentration of water as opposed to solid fiber content and do not store as well as long-day varieties (which predominate in northern states and have a more pungent flavor).
High temperatures and low humidity are advantageous for growing onions. Plants should be spaced to allow for adequate bulb growth.
Due to shallow roots, onions compete poorly with surrounding weeds and grasses. Timely and repeated weeding is recommended for optimal growth.
Pests & Diseases
The onion fly looks similar to a small house fly and lays eggs in seedlings or soil at the base of plants. The maggots cause the leaves to go pale, wilt, and die off as the inside of the bulb rots causing plants to die.
The lesser bulb fly is a similar but smaller species of fly that infects plants and should be eradicated before its maggots are able to burrow back into the soil.
Thrips cut into leaves and stems, sucking sap and leaving white silvery blotches on deformed leaves. Females can reproduce without a male.
Botrytis neck rot is a watery decay starting at the neck and moving downward to the bulb. Black mold is often associated with bruising and characterized by dark discolorations and shriveling. It can lead to bacterial soft rot, a watery, foul-smelling rot.
Harvesting at full maturity, proper drying and curing, minimal bruising and scraping, and maintaining proper storage conditions can prevent incidence.