Revised 1/01 -- Author Reviewed 1/01 HIL-18
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.
Soils - 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 multi-plier 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.
Fertilizer - Apply 300 to 500 lb of 10-20-20 per acre in rows 7 to 10 days before planting. Side-dress with 20 to 25 lb of nitrogen three weeks after plant emergence and every 3 weeks for 3 total applications.
Spacing - 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.
How To Plant - One of four general methods may be used. They are listed in order of easy stand establishment.
Weed Control* - 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 excellent weed control.
Disease 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.
Insect Control* - Thrips are a common pest of onions and should be controlled.
Harvesting - Harvesting usually begins in late fall and continues to late spring. When the white bulbs are one-half to one inch in diameter the onions can be harvested. Undercut with a blade prior to harvest to make harvesting easier. 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. 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."
General - Bunching onions respond to irrigation and fertilizer. The most successful growers manage both of the factors to keep onions growing rapidly. By "pushing" this crop, the green onions mature more rapidly and a grower can get more from a unit of land and reduce harvest labor by harvesting only once.
Forcing - Some growers get 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.
Published by the North Carolina Cooperative Extension Service