Green Onion Production in California

Abstract

Green onions (Allium cepa L.) are produced mainly in Monterey, Riverside, and Ventura Counties, but there is also small-scale production in other parts of the state. Harvest and bunching of this crop is labor intensive, and over the last several years substantial production has moved to Mexico, where the crop is less expensive to produce. Green onions are planted from spring through fall for nearly year-round harvest. CLIMATIC REQUIREMENTS Onions are cool-season biennial plants (requiring two seasons to complete the cycle from seed to seed) that are commercially grown as an annual crop. Bulbing and growth are highly sensitive to day length. Each variety has a critical day length at which bulbing is initiated, regardless of size. As days lengthen in the spring and summer, these critical day lengths are reached. Growth is also dependent on temperature. The minimum for emergence is higher than for most other cool-season vegetables, at 55ºF (12.8ºC) for 70 percent emergence in up to 2 weeks. In addition, early growth rate is slow compared with other coolseason crops. Optimal leaf growth rate occurs at 68º to 77ºF (20º to 25ºC). However, the total plant growth rate depends on the amount of light intercepted. Combinations of factors, including variety, stem size, temperature, and duration of temperature, determine bolting susceptibility. Onions are stimulated to bolt at temperatures of 45º to 50ºF (7.2º to 10ºC). VARIETIES Few public onion breeding programs exist in the United States (none in California), but private seed companies are involved in onion variety development. The emphasis of variety development is on hybrid types. Green onion varieties are generally classified according to day length (short-and long-day types). Long-day white varieties of Sweet Spanish or Southport White Globe are grown as green onions in areas with short days. Short-day varieties bulb too easily to be used for green onion production. Many hybrids have been developed by crossing Allium cepa with A. fistulosum, the nonbulbing Japanese bunching onion. These hybrids are most commonly grown in spring and summer in the Salinas Valley, and occasionally during winter in the southern desert regions and in Baja California, Mexico. Green onion production in areas with long days or during the summer months is most successful with the use of varieties with Japanese bunching onion parentage. White Sweet Spanish and Southport White Globe types are also sometimes grown in intermediate-and long-day growing regions. PLANTING Green onions are planted in dense stands on beds 40 or 80 inches (1 or 2 meters) wide. The crop is seeded in dense plantings with 18 to 20 seed lines on 80-inch beds. Seed is planted approximately 0.5 inch (12.5 mm) deep; this shallow planting requires a soil surface that is well prepared and that is kept moist through germination. Onion seed is susceptible to loss Vegetable Production Series vric.ucdavis.edu

Response of onion (Allium cepa L.) to plant population and weed control methods in a chicken weed (Portulaca quadrifida L.) infested field In Sudan Savanna, Nigeria

“…(Norman, 1992;Anyanwu, 2003). Carlson and Kirby (2005), Qasem (2006) and Smith et al (2011) confirmed that many authors have reported that onion plants are poor weed competitors and the poor competitive ability of the crop with weeds has been attributed to its initial slow growth and lack of adequate foliage to smother weeds. The establishment of optimum population per unit area of the field is reported by (Singh and Singh, 2000) to be an essential factor that leads to maximum yield.…”