Container Growing Onions: Pot Size, Soil & Watering

Onions adapt well to containers if you give them depth and consistent moisture.

Container Specs

• Diameter: ≥ 8 inches (allows 3–4 plants).
• Depth: ≥ 10 inches (critical for bulb expansion).
• Drainage: Multiple holes; elevate pot on feet.

Soil & Fertility

• High-quality potting mix + 20% compost.
• Slow-release balanced fertilizer at planting; liquid feed (fish emulsion) every 3 weeks.

Watering Rhythm

Keep soil evenly moist—never bone-dry, never soggy. Check daily; water when top 1″ feels dry (typically every 2–3 days in summer). Mulch surface with straw.

Harvest

• Green onions: pull anytime at pencil thickness.
• Bulb onions: wait for tops to yellow and flop (90–110 days). Cure 2 weeks in shade.

A 10-gal fabric grow bag works beautifully for a dozen onions.