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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).

CULTIVATION

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.

Seasonal Availability Chart
Seasonal Availability Chart

Storage & Packaging
Onions are harvested when most of the tops have fallen over. To prevent damage and bruising, harvesters gently lift onions out of the soil and place them in long rows to dry in the field (weather permitting).

Optimum temperature for field curing is 75°F with 75 to 80% relative humidity. Mild onions will store for up to 1 month at 32°F while pungent onions will store for up to 6 to 9 months.

Optimum relative humidity in storage is 65 to 70% with adequate air circulation.

References: Clemson Cooperative Extension, National Onion Association, PennState Extension, Texas A&M AgriLife Extension, UC Davis Postharvest Technology Center, University of Georgia Extension, USDA.

GRADES & GOOD ARRIVAL

There are three grades for dry onions: U.S. No. 1, U.S. No. 2, and U.S. Combination. To earn a U.S. No. 1 designation, onions must possess similar varietal characteristics and be mature, fairly firm, well shaped, and free from decay and damage.

For U.S. No. 2, onions will have similar varietal characteristics, not be overly soft or spongy, and free from decay and serious damage; U.S. Combination onions are a mix of the first two designations with at least half of the group, by weight, meeting U.S. No. 1 requirements.


Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the USDA or CFIA inspection was timely; and (3) the entire lot was inspected.

ONIONS: GRANO/GRANEX

U.S. Grade Standards Days Since Shipment % of Defects Allowed Optimum Transit Temp. (°F)
10-2 5
4
3
2
1
15-4
14-4
13-3
11-2
10-2
32°

ONIONS: OTHER

U.S. Grade Standards Days Since Shipment % of Defects Allowed Optimum Transit Temp. (°F)
5-2 5
4
3
2
1
8-4
8-3
7-3
6-2
5-2
32°

Canadian good arrival guidelines (unless otherwise noted) are broken down into five parts as follows: maximum percentage of defects, maximum percentage of permanent defects, maximum percentage for any single permanent defect, maximum percentage for any single condition defect, and maximum for decay. Canadian destination guidelines for all onions are 10-5-5-10-4.

References: DRC, PACA, USDA.

Onion Retail Pricing:
Conventional & Organic Per Pound


This information is for your personal, noncommercial use only.