How to Grow Onion Sets From Seed

Sets are small immature onions that are picked at the green stage, when the bulbs are just starting to develop and are approximately 1/2 to 1 inch in diameter. Onion sets can be stored indefinitely in a cool, dark, dry place, and replanted the following season to produce a mature crop of onions in less time than it would take if growing them from seed. Sets can also be planted in the fall, and if heavily mulched, will winter over and start producing early the following spring. You can create your own sets from seed.

Things You'll Need

• Planting trays
• Starter soil
• Pencil
• Mister
• Plastic wrap
• Small trowel
• Newspaper
• Garden shears

Instructions

1. Fill planting trays with soil to an inch from the top edge. Poke holes in the soil with a pencil about an inch deep and an inch apart, and drop a seed in each hole. Pull the soil gently back over the seeds and mist lightly. Cover loosely with plastic wrap, and set trays in a dark warm place. Check periodically to see if the soil has dried out, and mist again if necessary.

2. Remove plastic wrap once the seeds have sprouted, and move the trays to a sunny window. Move seedlings to the garden when they are about 2 to 3 inches tall. Use the small trowel to gently lift seedlings from the trays, poke holes about an inch deep and 1/2 inch apart in the soil with your finger, and place a seedling in each hole. Draw the soil up gently around the seedlings, and water lightly.

3. Harvesting the young onions from the soil when their tops are about 8 to 10 inches tall. Slide the small trowel under the onions, and lift them gently. Shake them to release some of the soil, and spread them out on newspaper and a warm dry place, making sure they don't touch each other.

4. Allow the onions to dry for several days, or until the skin on the bulbs has started to turn brown. Cut the green tops off the onions with the garden shears, leaving about an inch of stalk. Spread the trimmed onions out on the newspaper, and allow them to dry a few more days until they are completely dry, and feel like thin paper when touched.

5. Store the dried onion sets in baskets or mesh bags in a cool, dark place at a temperature of 35 to 40 degrees F.

Tips & Warnings

• Be sure to buy seed that will produce full-sized onions and not scallions, which do not produce bulbs that can be dried as sets. Seed packets will be labeled with such varieties as red, sweet, or yellow onions. Scallions will be labeled clearly, or are sometimes called spring or green onions.

• Onion seed can also be sown directly in the garden in early spring and treated the same way as seedlings. The seed can be planted outside as soon as the soil can be worked and is no longer frozen, which is generally about four weeks before the last frost.

References

• University of Illinois Extension: Onion
• Fosters.com: Growing Onions from Seed Not That Hard
• Gardening Know-How: Growing Onion Seed