Field guide
How to grow onions: planting, care, and harvest guide
Onions typically reaches first harvest in 90–120 days. This guide covers when to plant by USDA zone, common pests, harvest cues, and companion plants where relevant.
Open plannerWhen to plant onions by USDA zone group
- USDA Zones 1–4 — April to May
- USDA Zones 5–6 — March to April
- USDA Zones 7–8 — February to March
- USDA Zones 9–10 — January to February
- USDA Zones 11–13 — October to December
Companion plants
Good companions: Carrots, Lettuce, Beets, Tomato (Slicing)
Avoid planting with: Peas, beans
Harvest
When to pick
- Tops fall over naturally and begin to yellow
- Neck softens at the soil line
- Bulb feels firm and has reached expected size
How: Stop watering 1-2 weeks before harvest. Pull or dig bulbs. Cure in a warm, dry, airy spot for 2-3 weeks until necks are dry and papery.
Storage: Store cured onions in mesh bags in a cool, dry place. Sweet onions last 1-2 months; storage varieties last 3-6 months.
Common pests and problems
Onion Thrips
Signs: Silvery streaks on leaves, distorted growth, tiny slender insects
Control: Spray with insecticidal soap or spinosad. Reflective mulch deters thrips. Keep weeds down.
Onion Maggots
Signs: Wilting, yellowing plants that pull out easily; maggots in the bulb
Control: Use row covers. Rotate crops on a 3-year cycle. Apply beneficial nematodes.
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