When onions are harvested in the green or immature stage they are called "green bunch onions." These onions are sold in bunches tied with a rubber band. This is a popular crop for home and market gardeners in the fall, winter and early spring. Acreages are usually small because of the amount of hand labor required for planting and preparation for market.
Any fertile, well-drained soil is suitable for bunch onions. Since this is a shallow rooted crop, soils high in organic matter give much better results, unless irrigation is available. Soil pH should be 6.0 to 6.5.
From sets -- Use Silverskin (or White Portugal), Yellow Globe Danvers or Ebenezer.
From seed -- Use Beltsville Bunching, White Lisbon, Sweet Spanish. Tokyolong and Ishikuri are good for overwintering. Some growers still use multiplier onions. Shallots (similar to multiplier onions) are also used in some areas, but they do not produce stems as large as onion varieties, and thus are not popular on southern markets.
Commercial growers -- Apply 300 to 500 lb of 10-20-20 per acre in rows 7 to 10 days before planting. Sidedress with 20 to 25 lb of nitrogen three weeks after plant emergence and every 3 weeks for 3 total applications.
Gardeners -- Apply 2 to 3 lb of 10-10-10 per 100 square feet 7 to 10 days before planting. Sidedress with 3 to 4 oz of nitrogen three weeks after plant emergence and every 3 weeks for 3 total applications.
Plant on beds 4 to 6 inches high for good drainage. Row spacing can be 2 rows per bed on 38 inch centers or 4 rows per bed on 60 to 76 inch centers. If 2 rows per bed are used space rows 9 to 12 inches apart (allow room for cultivation between rows). If 4 rows per bed are used space rows 9 to 18 inches apart. For sets or seed, spacing in the row should be 1 to 2 inches. Transplants should be spaced 2 to 4 inches in the row.
One of four general methods may be used. They are listed in order of easy stand establishment.
Plant sets (about 3⁄4-inch in diameter) any time from September through February. The larger the sets, the sooner the green onions are of size. Large sets tend to form seed stalks earlier than smaller sets. In the early fall and late winter, onions can be produced in 6 to 8 weeks.
Plant seed in protected beds in September and set in the ground when plants are about 6 inches tall. Seed 12 to 18 seeds per ft of row, in rows 4 to 6 inches apart. It takes about 4 to 6 weeks for the plants to get large enough to set and then an additional 6 to 10 weeks for market size plants.
Seed directly in the field or garden in late winter and then thin to proper stand when plants are 2 to 3 inches high. This method is not used for fall or early winter harvest. It will take 12 to 18 weeks to produce a crop, depending on how frequently you fertilize and irrigate.
Buy plants for setting anytime from September through March. This method is used primarily by gardeners for winter and spring onions.
Cultivate shallow; only enough to control weeds. Two to 3 weeks before harvest approximately two inches of soil should be worked around the base of the stem. This is known as blanching and results in onions that have a longer "white and tender" stem. Herbicides are available for growers with excellent weed control.
Downy mildew can be a problem in late spring and summer crops. Use good fungicide and high pressure (200 psi) for control of diseases.
Harvesting usually begins in late fall and continues to late spring. When the white bulbs are 1⁄2- to 1-inch in diameter the onions can be harvested. To make harvesting easier, growers undercut onions with a blade and gardeners loosen onions with a fork beforehand. Pull off the discolored outside skin leaving the basal part of the plant white and clean.
Growers should check with their markets to determine the size of green onions their particular market prefers. Tie in small, neat bunches (5 to 7 per bunch) with a soft string, tape or rubber band. Trim the yellow leaves and tips off of the tops and pack in crates for sale.
The quality and color of green onions deteriorates very rapidly, thus the onions should be kept cool for nearby sales and placed under refrigeration for distant markets. Crushed ice is used in some instances. Gardeners should harvest onions shortly before use.
During the late spring and early summer, many onions are pulled when the bulb is about the size of a half dollar piece, the roots and tops trimmed, then they are bunched and sold locally as "stewing onions."
Bunching onions respond to irrigation and fertilizer. The most successful growers manage both of these factors to keep onions growing rapidly. By "pushing" this crop, the green onions mature more rapidly, increasing the yield per unit of land. This allows commercial growers to reduce harvest labor by harvesting only once.
Some achieve rapid growth with uninjured tops by planting onion sets in protected beds. Protection may consist of anything from a hedge row or building as a windbreak, to covered coldframes or even plastic greenhouses. When onions are "forced" in such beds, they are often mulched with straw, sawdust or other organic material to reduce weed growth since they are planted very close together (about 3 x 3 inches) and cultivation would be difficult.
* For all pest management recommendations check the latest issue of the NCCVR (North Carolina Commercial Vegetable Recommendations, AG-586) or your county Extension center.
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.
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Last modified: Dec. 16, 2014, 1:43 p.m.