How Far Apart Should Onion Sets Be Planted?

by Ellen Douglas

Onions bulbs need more space than scallions.

When it comes to planting onions, you have a choice of how to start the pungent vegetables. They come as seeds and started seedlings. Another option, however, is to plant sets, which are tiny onion bulblets. The spacing for planting onion sets is crucial, because you need much more room to grow bulb onions than you do to grow scallions.

About Sets

Sets are available for several allium types, including red and white onions. The onion sets can be grown for either the above ground or below ground parts of the plant. In other words, they can become scallions -- also known as green onions or onion tops -- or bulb onions. If you plan to grow both, separate the sets when they arrive -- they often come as mixed varieties. Larger sets work best as scallions, while those smaller than a nickel make better bulb onions.

Planting Onions

The depth for which you plant sets when growing onions is determined by the size of the sets themselves. Dig a hole to a depth that allows the tip to sit just above the soil's surface. Spacing should be at least 5 inches apart within the row. If you plant more than one row, space rows at least 1 foot apart.

Planting Scallions

The holes you dig for scallions should be no more than 2 inches deep. Because bulb development is not your goal, the sets can be much closer together. Space onion sets for scallions as close as 1 inch apart, in rows that are about 1.5 feet apart.

Timing

It not only takes less space to produce scallions than onions, it also takes much less time to develop onion tops than for the bulbs themselves to turn into full-sized onions. Expect the scallions to mature in three to four weeks. Traditional onions need three to four months to develop. In U.S. Department of Agriculture plant hardiness zones 8 to 10, scallion sets, which prefer cool weather, can be grown in both spring and fall. Set them into the ground in April for spring harvest and August or September for fall harvest. Plant sets for bulb onions starting in September. They can be planted all the way through March.

About the Author

Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.

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