The Homeowners Column

The Homeowners Column

Time to plant onions

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator
slmason@illinois.edu

You can broil 'em, boil 'em, bake 'em and flake 'em; cream 'em, steam 'em, fry 'em and dry 'em. If you are itching to plant something, consider the versatile onion. Late March through early April is the perfect time for planting onions.

Onions can be grown from seeds, sets (baby bulbs) or transplants (baby plants). Seeds take the longest to produce so most gardeners stick with sets or transplants. However many more varieties are available as seed than as sets or transplants. The simplest method is growing green onions from sets. Dry onions can also be produced from sets; however the best storage onions develop from transplants.

Several varieties are used for onion sets. Unfortunately they lose their varietal identity by the time they arrive at garden centers where yellow, white or red are the only choices. Purchase firm, dormant sets. If necessary, store sets in a cool, dry, dark place before planting. Most gardeners prefer white sets for green onions, but red or yellow sets can also be used.

When purchasing sets select the size according to your desire for green onions, dry onions or both. Onion sets larger than a dime in diameter are best for green onions. Large sets may form flower stalks which translates into poor onion storage. The small sets, smaller than a dime, produce the best bulbs for large, dry onions. Divide the onion sets into two sizes before planting.

To produce green onions, plant the larger sets shoulder to shoulder at one and one half inches deep. As a space saver I plant my green onions between my broccoli plants. The green onions are in salsa and salad long before the broccoli gets big.

To produce dry onions, plant the smaller sets 1 inch deep, with 2 to 4 inches between sets. If sets are planted 2 inches apart, harvest every other plant as green onions to alleviate crowding and allow bulb formation.

Onion transplants produce the best dry storage onions. Transplants are sold in bundles of usually 60 to 80 plants. Five or six different varieties are available as transplants. In general look for long day varieties. Onions start bulb formation when the day length is of the proper duration and different varieties of onions require different day lengths. Long-day varieties are usually best for our area and short-day varieties are best grown in the southern U.S.

Plant transplants 1 to 1 1/2 inches deep. Space transplants 4 to 5 inches apart in the row to produce large-sized bulbs (closer spacing significantly decreases bulb size) or space 2 to 2 1/2 inches apart and harvest every other plant as a green onion. Allow 12 to 18 inches between rows or space onions 6 to 8 inches apart in all directions in beds.

To develop long, white stems for green onions, slightly hill the row by pulling the loose soil toward the onions with a hoe when the tops are 4 inches tall. Do not hill onions that are for dry storage. Hilling can cause the necks of the stored onions to rot.

Green onions can be harvested as soon as the plants are 6 inches tall. Green onions develop stronger flavor with age. All parts above the roots are edible.

Harvest dry onions in late July or early August, when most of the tops have fallen over naturally.

Onions have few insects and diseases, but require fertile well drained soil and do not compete well with weeds. Check out UI Extension website for more vegetable gardening tips. http://web.extension.illinois.edu/state

March 26 and 27, 2010 Spring into Gardening with Garden Day 2010; I-Hotel and Conference Center, Champaign, IL. Enjoy nationally known speakers and shop among unique garden vendors and artisans. To register Champaign County UI Extension www.extension.uiuc.edu/champaign PH: 217-333-7672.

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