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.
References: National Onion Association, PennState Extension, University of Georgia Extension.
TYPES, VARIETIES & CUTS
Highly adaptable, onions are grown successfully throughout much of North America. Dry onions refer to large, bulbous onions with a shiny outer layer of skin and are sold in stores as yellow, red, or white.
Short-day varieties (Bermuda/Grano/Granex) are typically grown in southern states where temperatures are warmer 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).
References: National Onion Association, Texas A&M AgriLife Extension Service, University of Georgia Extension.
PESTS & DISEASE
Botrytis neck rot is a watery-decay that initiates at the neck and moves downward to the bulb. Grey fungal growth is visible at the neck and outer scales. Black mold is often associated with bruising and characterized by black discoloration and shriveling. Black mold will lead to bacterial soft rot, a watery, foul-smelling viscous rot. Harvesting at full maturity, proper drying and curing, minimal bruising and scraping, and maintaining proper storage conditions to prevent condensation will generally control these bacterial rots.
The onion fly looks similar to a small house fly and lays its eggs in seedlings or soil at the base of plants. The maggots cause the onion leaves to go pale, wilt, and die off; the inside of the bulb becomes rotten causing the plant to die. Lesser bulb fly is a similar, but smaller fly. Infected plants should be completely removed before maggots burrow back into the soil. Thrips cut the epidermis of the leaves or stems and eat the plant sap, leaving white silvery blotches on deformed leaves. Females can reproduce without a male.
References: Clemson University Cooperative Extension Service, PennState Extension, UC Davis Postharvest Technology Center.