Revised 1/01 -- Author Reviewed 1/01 HIL-8018
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.
Fertilizer -- Apply 2 to 3 lb of 10-10-10 per 100 ft2 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.
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.
Disease Control* -- Downy mildew can be a problem in late spring and summer crops. Use a good fungicide 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. Loosen onions with a fork before harvest. Pull off the discolored outside skin leaving the basal part of the plant white and clean. The quality and color of green onions deteriorates very rapidly, thus the onions should be harvested 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 can be used as "stewing onions".
General -- Bunching onions respond to irrigation and fertilizer. The most successful gardeners manage both of these factors to keep onions growing rapidly. By "pushing" this crop the crop matures more rapidly and a gardener can get more from a unit of land.
Forcing -- Some gardeners 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 information on pest control, consult your county Extension agent or the current issue of the NCCVR (North Carolina Commercial Vegetable Recommendations, AG-586) .
Published by the North Carolina Cooperative Extension Service