Vegetable Grow Guides
How to Grow Organic Onions (from Seed) from Seed
Allium cepa
About Onions (from Seed)
Bulbing is triggered by day length, not by “soil that is too cool.” Short-day types for the South (Zones 8–10); intermediate for the mid-latitudes; long-day types for the North (Zones 3–6). Cool weather can cause bolting, especially after a warm spell. Choose the day-length class that matches your region.
When to Plant
Start indoors 8–10 weeks before last frost. Transplant 2–4 weeks before last frost. Direct-sow only where the season is long enough for the variety.
How to Plant
Sow ¼ inch deep. Transplant 3–4 inches apart (not 16 per square foot), rows 12–18 inches. Set transplants no deeper than they grew. Keep weeded — onions lose to grass. Even moisture until tops fall.
When to Harvest
When 50–80% of tops have fallen, lift bulbs, cure in a warm, airy shade 2–3 weeks, then store cool and dry. Do not wait for a “nearby image” — harvest by the tops and the firmness of the bulb.