- The most commonly eaten species of the Allium genus that includes garlic, leek and onion.
- All cultivars derive from a probably extinct ancestor.
- Can withstand high salinity levels but will grow only after the salinity level has subsided.
Onion is a biannual or perennial plant that is usually treated as an annual plant: it is harvested in the same season as it is planted. Onions are either planted as seedlings, as small bulbs or, in some regions in the world, as a seed. There are many varieties of onion and onions are closely related to other commonly consumed vegetables such as leek, garlic, shallot and chive. Many people get irritable eyes when they cut onions, which is part of e defence mechanism of the onion.
Onions require a loose, sandy or loamy soil that is high in nutrients. They have relatively high demands for nitrogen and potassium. Onions are sensitive to daylight, which is the trigger to start making the bulb. Onions have a shallow root system and do not require a lot of water after they have been established.
Onions are a bit more sensitive to salinity than carrots and potatoes. They can withstand high salinity levels for some time but will not grow during that period; growth will resume after the salinity peak has passed.