How to Grow & Harvest Onion Sets

All onion sets are grown from seeds.

Planting onion sets produces scallions and large bulb onions. Onion sets are produced from planting seed in the midsummer of the growing season. The sets are then stored over the winter and then planted back into the soil as early as the season will allow. While onions can tolerate cold temperatures, leaving onion sets in the garden over the winter may cause the onions to bolt (produce large flower tops) instead of producing large bulbs.

Things You'll Need

• Shovel
• Organic compost
• Super phosphate 0-20-0
• Garden rake
• Onion seeds
• Peat moss
• Water
• Scissors

Instructions

1. Dig a small garden bed that is approximately 3 feet square. Make the bed as deep as possible. Remove all errant weeds, roots and rocks.

2. Add 2 inches to 3 inches of organic compost over the small growing bed. Dig the material into the soil. Sprinkle 1/2 cup of the super phosphate over the bed. Rake the material into the soil with a garden rake.

3. Broadcast approximately 1/4 ounce of onion seed evenly over the bed. Cover the seeds with a 1/4-inch layer of peat moss. Keep the bed moist.

4. Roll the tops of the small onion leaves over to the ground after two months of growth. This forces the small onions to form bulbs.

5. Leave the small onion sets to grow until they reach the size of a dime or nickel. Cut the tops with scissors 1/2 inch from the bulb. Remove the sets from the soil. Place the sets in a cool, dry environment. Allow the bulbs to fully cure. The sets are cured when the cut top is dry and a thin layer of paper forms over the small bulb set.

Tips & Warnings

• Germination temperatures for onion seeds range between 45 degrees and 95 degrees Fahrenheit. Generally, if the seedbed is kept moist and temperatures are acceptable, small green tops will begin to emerge four to five days after planting.

References

• "Encyclopedia of Organic Gardening"; J.I. Rodale; 1975
• Texas A&M University: Onion Planting
• Cornell University: Onions