Onion

Onion

　　   Onion, also known as bulb onion, round onion, jade onion, or spring onion, and called "Dutch onion" in English (onion), belongs to the genus Allium of the Amaryllidaceae family and is a biennial herbaceous plant. There are many theories about the origin of the onion, but most believe it likely originated in the highland regions of Central and Western Asia, particularly Iran and Afghanistan in the southwestern part of Asia Minor and Asia Minor, because wild varieties of onions can still be found in these areas today.

The origin of the onion dates back over 5,000 years. It was introduced to Egypt around 1000 BC, later spread to the Mediterranean region, arrived in the United States in the 16th century, reached Japan in the 17th century, and was introduced to China in the early 20th century.

Onions are widely cultivated across China, from north to south, with planting areas continuously expanding. They are currently one of the main vegetable crops grown in the country. China has become one of the world’s top four onion-producing countries (China, India, the United States, and Japan). Major onion-growing regions in China include Shandong, Gansu, Inner Mongolia, and Xinjiang.

Because onions originated in continental climate zones—where climate changes are intense, air is dry, and soil moisture varies significantly by season—the species has undergone corresponding morphological adaptations during its evolutionary development. These include a shortened stem plate, moisture-loving roots, drought-resistant leaf types, and storage-capable bulbs. Physiologically, onions have also developed certain adaptive traits. During their vegetative growth phase, they require cool temperatures, moderate light intensity, loose, fertile, water-retentive soil, low air humidity, and higher soil moisture. They exhibit characteristics such as cold resistance, moisture preference, and fertility preference, but are intolerant of high temperatures, strong sunlight, drought, and poor soil. Under conditions of high temperature and long daylight, onions enter a dormant phase.

The edible part of the onion is its enlarged underground bulb (i.e., the onion itself). Based on skin color, onions can be classified into three types: white-skinned, yellow-skinned, and red-skinned. White-skinned onions have small bulbs, with outer skins that are white or slightly greenish, tender flesh, juicy texture, mild spiciness, and excellent quality, making them suitable for raw consumption.

While many people in China are wary of its distinctive pungent aroma, onions are hailed abroad as the “queen of vegetables” and are highly nutritious.

Quality requirements for onions: A good onion should have a large, firm bulb with glossy skin, free from rot, mechanical damage, or dirt. Fresh onions should not have leaves attached. After storage, the bulb should remain firm, not sprout, have tightly packed layers, low moisture content, and a strong flavor that is both spicy and sweet. Cutting an onion often brings tears to the eyes.