Garden onion

Overview

The garden onion, Allium cepa, is a bulb-forming vegetable in the genus Allium, which also includes garlic, leeks, and shallots. It is the most widely cultivated species of onion and is used globally as a foundational aromatic and vegetable. The bulb has layers of fleshy leaves with a pungent, sulfurous flavor that becomes sweet and mild when cooked.

Origin and history

The garden onion is believed to have originated in Central Asia, likely in the region spanning modern-day Iran, Pakistan, and the mountainous areas of Tajikistan and Uzbekistan ^[1]. It has been cultivated for over 5,000 years and was known to ancient Egyptian, Greek, and Roman civilizations, where it was used as both food and medicine ^[2]. Onions spread through trade routes across Europe, Asia, and Africa, and were brought to the Americas by European colonists. The Latin species name cepa simply means “onion” ^[1].

Varieties and aliases

• Bulb onion or common onion (the standard garden onion)
• Yellow onion (most common storage variety, brown-skinned)
• Red onion (purple-skinned, milder flavor)
• White onion (white-skinned, sharp flavor, common in Mexican cuisine)
• Sweet onion (low-sulfur varieties such as Vidalia, Walla Walla, Maui)
• Spring onion or scallion (immature Allium cepa harvested before bulb fully forms; also refers to Allium fistulosum)

Culinary uses

The garden onion is a universal aromatic base in cuisines worldwide. It is used raw in salads, salsas, and sandwiches, or cooked by sautéing, roasting, caramelizing, frying (as onion rings), or pickling. In Mexican cuisine, white onion is the standard choice for pico de gallo, tacos, and caldo de res. In French cuisine, the onion is the base of mirepoix (with carrot and celery) and the star of French onion soup. In Indian cuisine, onions are fried as a base for curries and used raw in salads and raita. Onions pair with garlic, tomatoes, chiles, herbs, and meats.

Cross-cuisine context

The garden onion has no single direct analogue in any other cuisine because it is itself the global standard. However, in Mexican cuisine, the white onion is the closest equivalent to the yellow onion used in European and American cooking, though the white variety is preferred for its sharper, cleaner bite in raw applications. In East Asian cuisines, the Japanese bunching onion (Allium fistulosum) is used in similar ways but is a different species with a milder, grassier flavor. In Persian cuisine, the garden onion is used extensively in khoresh (stews) and as a raw accompaniment to kebabs, much as it is used in Mexican cebollitas asadas (grilled green onions).

Notes for cooks

• Yellow onions are the best all-purpose choice for cooking; red onions are milder and better raw; white onions are often considered the sharpest and are commonly preferred for Mexican salsas.
• Store whole onions in a cool, dry, dark place with good air circulation; most experts recommend against refrigerating them, but cut onions should be refrigerated in a sealed container.
• The pungent compound that causes eye irritation is syn-propanethial-S-oxide ^[1], released when onion cells are cut. Chilling the onion before cutting or cutting under running water can reduce this effect.