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How to Grow Onions from Sets

easyGardeninghalf day

Learn how to successfully cultivate homegrown onions using sets with this straightforward guide for gardeners of all skill levels. You will discover the ideal soil conditions, planting schedules, and spacing techniques required to ensure a bountiful harvest.

Safety Warnings

  • Onions contain N-propyl disulfide, which is toxic to dogs, cats, cattle, and horses.

Tools Needed

Trowel — Hand-held digging tool
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Garden Hoe — Used for cutting weed tops
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Materials

Onion sets or seeds — Variety matched to growing zone (long-day or short-day)(Variable)
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Balanced fertilizer — 10-10-10 NPK ratio(As per package directions)
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Compost — Well-rotted organic matter(A few inches for soil mixing)
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Steps

1
Prepare the garden bed by ensuring the soil is well-draining and loose with a pH between 6.5 and 6.8. Mix in a few inches of compost and apply balanced fertilizer before planting.
2
Plant onions in early spring (late April to early May) once the soil can be worked. Ensure the location receives full sun, ideally up to 13 hours a day depending on the variety.
3
For onion sets, create holes 1 to 1.5 inches deep and 4 to 6 inches apart in rows spaced one foot apart. Plant sets with the pointed end facing up and cover with one inch of soil.
Tip: Separate sets and use those smaller than a penny for bulb growth; save larger sets for green onions.
Pointed end up 1-1.5" depth 1" soil cover cover with soil Cross-section: Plant onion sets pointed-end up at specified depth
4
Maintain consistent moisture by providing at least 1 inch of water per week. Water if the soil feels dry 1 inch beneath the surface, using a drip system or soaker hose to avoid soggy soil.
5
Apply a second dose of balanced fertilizer 4 to 5 weeks after planting. Place the fertilizer in a narrow band 2 to 3 inches from the plants.
Tip: Avoid hilling soil up around the base of the plant to reduce the risk of disease.
2-3" Onion set Fertilizer Apply band Side-dressing · Place fertilizer 2-3 inches away from base to avoid bulb burn
6
Harvest when two-thirds of the dried top leaves have laid over on the ground. Carefully pull or dig them up using a trowel to avoid damaging the bulb.
7
Cure the onions by laying them in a well-ventilated, shaded area out of direct sun for up to 2 weeks until roots and stems are dry and crispy.
8
Store cured onions in a cool, dry location (32 to 45 degrees Fahrenheit) such as a root cellar or unheated garage. Keep them in mesh bags for airflow and do not refrigerate.

Pro Tips

  • Match onion varieties to your hardiness zone (5-10) and available daylight hours (long-day vs short-day).
  • To prevent black mold and other diseases, rotate the location of your onion patch each year.
  • Use a hoe to cut off weed tops rather than pulling them, as tugging can damage the onion's fragile root system.

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