When to plant onions
Short answer
Plant onions about 4 weeks before your last spring frost. In a mid climate (zone 5) that's around Mar 18, starting seeds indoors about Feb 4. Enter your ZIP for your exact dates.
| Climate zone | Start indoors | Plant outside | Harvest |
|---|---|---|---|
| Zone 1 | Jan 1 | Jan 1 | Mar 28 |
| Zone 2 | Jan 1 | Jan 18 | Apr 28 |
| Zone 3 | Jan 1 | Feb 10 | May 21 |
| Zone 4 | Jan 19 | Mar 2 | Jun 10 |
| Zone 5 | Feb 4 | Mar 18 | Jun 26 |
| Zone 6 | Feb 19 | Apr 2 | Jul 11 |
| Zone 7 | Mar 6 | Apr 17 | Jul 26 |
| Zone 8 | Mar 23 | May 4 | Aug 12 |
Higher climate-zone numbers are colder, so planting shifts later. Onions is a hardy crop. Enter your ZIP in the calculator for your exact zone and dates.
Your exact dates
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Frequently asked questions
When should I plant onions?
Sow onions directly about 4 weeks before your last spring frost — it tolerates cold. In a warmer zone 4 that's around Mar 2; in a colder zone 6, Apr 2.
When do I start onions seeds indoors?
Start onions seeds indoors about 10 weeks before your last frost, then transplant after the frost passes. That's roughly Feb 19 in zone 6.
How long until onions is ready to harvest?
About 100 days from transplant or sowing. In zone 6, plants set out around Apr 2 are typically ready near Jul 11.