Going Green Onion
Commnunity Contributed By Glenn I. Teves, UH County Extension Agent
Green onion is an important flavoring and garnish used in many island delicacies from poke to saimin. Known as the Welsh or foreign onion, it’s a member of the Lily family and also known by its Latin name, Allium fistulosum. Green onion is actually a perennial, but we usually grow it as an annual. What distinguishes the true green onion from other onion species is when cut it has a perfectly round leaf, while other onion species have leaves resembling the other phases of the moon. A good green onion will have a light pungency and a pleasant sweetness to it.
Native to Northwest China near the North Korean border and cultivated in China since 200 BC, green onion is still the most important onion of these areas. It’s grown in many parts of the world as a home garden vegetable. In Oriental medicine, parts of green onion are used to treat fever, inflammation, headaches, stomach aches and diarrhea. Diluted pressed juice is used to control aphids, a common pest of vegetables in China.
Green onion prefers neutral soil of pH 6-6.5 and higher elevations of 600 to over 2,000 feet for optimal growth, although it’s widely adapted. It likes well-drained soil and is very susceptible to water-logging. They have a fairly small root system and don’t compete well with weeds.
Onion thrips are a major pest causing unsightly silver-white lines on the leaves by piercing and rasping the leaf surface. Difficult to control, they thrive in hot weather and live under the leaf sheath where the leaves branch. Part of the life cycle is also spent in the ground. At high populations, the plants lose lots of water from the damage and can desiccate. Using seed instead of divisions and planting in new areas away from old plantings can help to minimize thrips since they can live in planting material. Other occasional pests include the beet armyworm and the serpentine leaf miner.
Diseases include purple blotch, an Alternaria fungus attacking leaves with its characteristic purple blotch on the stalk. The key in controlling many disease problems is to grow a healthy plant, and make sure your nutrition program is well tuned for the different seasons.
By growing them in close spacing, leaves can be kept small. Seed varieties grown in Hawaii include Koba and Fragrance, while many local types are grown by division. Shallots are sometimes grown for it leaves, including the Hawaiian onion or Akakai and the Filipino shallot. Major green onion production areas in Hawaii include the Leeward Coast valleys of Oahu, from Lualualei to Waianae. Growing them in pots in proximity to your kitchen assures a steady and readily available supply of green onion.