How to grow Onion

At a glance

🌱 Grow your Onion with GardenDex

• Reminders to water it, timed to your weather and whether it's in a pot
• Frost and disease alerts for your garden, the night before
• Follow it from seed to harvest, and see what your garden grew in $
• Point your camera at any plant or bug to identify it

🗓️ When to plant

Plant onion sets or transplants in early spring as soon as soil is workable, or sow seeds indoors 6–8 weeks before the last frost. In mild climates, plant in mid-autumn for winter harvest.

🌰 How to plant

1. Prepare soil by mixing in compost and ensuring good drainage.
2. Plant sets with the pointed end up, just barely covered with soil, at proper spacing.
3. Water gently after planting and keep soil evenly moist until growth is established.
4. Apply a light mulch around plants, keeping it away from the bulb itself.

💧 Care

• Weed regularly by hand to avoid disturbing shallow roots.
• Once bulbs begin to swell, reduce nitrogen fertilizer to avoid delays in maturity.
• Stop watering about 2–3 weeks before harvest to help bulbs cure and store better.
• Thin crowded seedlings early so remaining plants have space to develop properly.

🧺 Harvest

Harvest when the foliage yellows and falls over naturally, usually in mid to late summer. Gently dig bulbs, allow them to cure in a warm, dry place for 2–3 weeks before storing in a cool location.

🐛 Common problems

Onion fly: Cover young plants with row cloth or use companion planting with garlic; remove affected bulbs promptly.

Downy mildew: Improve air circulation, avoid overhead watering, and remove affected foliage immediately.

Fusarium basal rot: Plant disease-resistant varieties and ensure excellent drainage to prevent fungal buildup in soil.

🤝 Companion plants

💚 Good neighbours: Carrot, Lettuce, Beet, Chamomile

⚠️ Keep apart from: Beans, Peas

More vegetables guides