Vegetables · biennial grown as an annual

Onion from seed

Allium cepa · also searched as green onions, bunching onions

Germination temperature: 65 to 85°F (18 to 29°C)
Minimum soil temperature: 32°F (0°C)
Sowing depth: ¼ in (6 mm)
Days to germinate: 7 to 12 days
Light: Either; light is not critical
Before sowing: Nothing needed
Start indoors: 8 to 10 weeks before planting out
Plant out: 2 weeks before the last frost
Sow outdoors: 4 to 2 weeks before the last frost
Spacing: 4 to 6 in (10 to 15 cm) for bulbs

Your dates from your last frost Seed not coming up?

Sowing

Onions from seed start slowly. Sow indoors 8 to 10 weeks before planting out (NDSU says 10 weeks before the last frost) at about 75 to 85°F, or direct early in spring. Sets (small bulbs) are simpler.

Care and transplanting

Plant out about 2 weeks before the last frost. Trim tops once or twice to keep them sturdy, keep weeded and shallow-rooted plants watered.

Problems

Seedlings flop if too tall; a haircut helps. Bulbs that bolt were chilled when young or small plants were set too early.

Saving seed

Onions flower in their second year. Collect the black seed from dry heads.