Onion

Growing Conditions

Growing Zones

Thrives in USDA Zones 3 - 10

Companion Planting

When to Plant

• Start Indoors

  10 - 12 weeks before last frost

• Transplant

  4 - 6 weeks before last frost

• Direct Sow

  Plant sets 4 weeks before last frost

• Harvest

  When tops fall over naturally; cure 2 - 3 weeks before storage

Organic Growing Tips

• Interplant with carrots - each deters the other's primary fly pest through aromatic confusion.

• Mulch lightly to retain moisture without keeping soil overly wet, which promotes neck rot.

• Cure bulbs thoroughly in a warm, airy place before storage to prevent rot.

• Avoid overhead irrigation; use drip lines to keep foliage dry and reduce disease.

Common Pests

• Onion Thrips
• Onion Fly
• Downy Mildew
• Neck Rot

Taxonomy

Kingdom

Plantae

Family

Onion family (Amaryllidaceae)

Genus

Allium

Species

Allium cepa

Natural History

Allium cepa, the common bulb onion, likely originated from wild relatives in Central Asia - possibly modern Uzbekistan, Pakistan, or Afghanistan - though no truly wild form of A. cepa has been definitively identified, suggesting domestication may have occurred early enough to obscure the wild ancestor. Onions appear in ancient Egyptian records from the 3rd millennium BCE and were depicted in tomb paintings. Herodotus recorded that an inscription at the Great Pyramid of Khufu listed the quantities of onions, radishes, and garlic consumed by the builders. Onion bulbs were found in the tomb of Ramesses IV around 1160 BCE. The ancient Greeks and Romans grew onions extensively; Pliny the Elder listed multiple varieties in Naturalis Historia. Bulbing in Allium cepa is governed by photoperiod - the length of daylight triggers bulb formation - which is why short-day, intermediate-day, and long-day onions must be matched to latitude rather than treated as interchangeable.

Traditional Use

Onion has been documented as a cultivated food plant since the earliest written records. Its preservation qualities, pungency, and year-round storage made it one of the most strategically important food crops in the ancient world - valued alongside garlic and leek as the foundational trio of alliums.

• Ancient Egypt and the Pyramid Workers - Bulbs

  Onions appear in Egyptian tomb paintings and inscriptions from the 3rd millennium BCE. Herodotus recorded an inscription at the base of the Great Pyramid of Khufu listing quantities of onions, radishes, and garlic consumed by the builders. Bulbs were found in the tomb of Ramesses IV (c. 1160 BCE). Some accounts suggest the layered structure of the onion held symbolic significance in Egyptian culture.

• Roman Agricultural Tradition - Bulbs

  Pliny the Elder described numerous onion varieties in Naturalis Historia, distinguishing them by flavor, size, and storage quality. Roman military provisioning relied heavily on onions for their durability on campaign. The Roman cookbook Apicius uses onions across a wide range of preparations, and the diversity of variety types Pliny describes shows that careful selection was already practiced in the 1st century CE.

• Medieval European Household and Food Tradition - Bulbs

  Onions were a cornerstone of medieval European food at every social level, appearing in the earliest surviving cookbooks alongside bread and meat. The 1390 English cookbook Forme of Cury includes onions in numerous preparations. In peasant economies, onions and alliums provided the primary flavoring for grain-based meals throughout northern Europe. Hanging braids of cured onions became a storage tradition documented in household records and depicted in paintings from the medieval period onward.

• French Regional Onion Culture - Bulbs

  France developed distinct regional onion varieties bred for specific culinary roles. The Roscoff pink onion of Brittany became the subject of one of the more colorful episodes in vegetable trade history: Breton onion sellers (Johnnies) who cycled through Britain selling strings of onions from their bikes, a tradition documented from the 1820s and continued into the 20th century. The image of the Breton onion man became one of the most persistent British caricatures of French identity.

Onions are toxic to dogs and cats. Safe as food for people, though cutting releases lachrymatory factor - a sulfur compound that causes eye irritation.

This information is provided for historical and educational purposes only and is not medical advice. Always consult a qualified healthcare professional before making decisions related to your health.

Morphology (Plant Structure & Identification)

• Root System

  Shallow fibrous roots spread from the basal plate and do not compete well with weeds. Even moisture and loose surface soil matter because roots stay near the top few inches.

• Stem

  The true stem is a small basal plate at the bottom of the bulb. The upright green top is formed by overlapping leaf bases that swell into bulb scales.

• Leaves

  Hollow, round, blue-green leaves with a waxy surface. Strong upright leaves feed bulb growth; bent or fallen tops are a maturity cue.

• Flowers

  Second-year plants send up a hollow flowering stalk topped with a round umbel of many small white to pale lavender flowers.

• Fruit

  Produces small black seeds in dry capsules after flowering. The harvested onion bulb is made of swollen leaf bases arranged in layers.

Known Varieties

Common cultivars worth knowing

• Walla Walla

  Large sweet long-day onion with mild flavor and limited storage life.

  Best for: fresh eating

• Yellow Granex

  Short-day sweet onion type associated with Vidalia-style production.

  Best for: warm regions, sweet onions

• Patterson

  Long-day yellow storage onion with firm bulbs and strong keeping quality.

  Best for: storage

• Red Burgundy

  Red onion with mild flavor and attractive rings.

  Best for: salads, fresh use

• Evergreen Hardy White

  Bunching onion grown for green stalks rather than large bulbs.

  Best for: scallions, overwintering

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