When to plant onions
Onions are a cool-season crop that tolerates light frost and prefers to grow in cool weather. Choose long-day varieties in the North and short-day varieties in the South.
- Start seeds indoors 10–12 weeks before the last spring frost.
- Transplant outside 2–4 weeks before the last spring frost.
About 100 days from planting to harvest.
Get exact dates for your garden
Planting dates by hardiness zone
| Zone | Typical last frost | Start indoors | Transplant | Fall crop |
|---|---|---|---|---|
| 2a | May 24 | Mar 1 – Mar 15 | Apr 26 – May 10 | — |
| 3b | May 17 | Feb 22 – Mar 8 | Apr 19 – May 3 | — |
| 4a | May 12 | Feb 17 – Mar 3 | Apr 14 – Apr 28 | — |
| 4b | May 8 | Feb 13 – Feb 27 | Apr 10 – Apr 24 | — |
| 5a | May 3 | Feb 8 – Feb 22 | Apr 5 – Apr 19 | — |
| 5b | May 1 | Feb 6 – Feb 20 | Apr 3 – Apr 17 | — |
| 6a | Apr 29 | Feb 4 – Feb 18 | Apr 1 – Apr 15 | — |
| 6b | Apr 22 | Jan 28 – Feb 11 | Mar 25 – Apr 8 | — |
| 7a | Apr 16 | Jan 22 – Feb 5 | Mar 19 – Apr 2 | — |
| 7b | Apr 5 | Jan 11 – Jan 25 | Mar 8 – Mar 22 | — |
| 8a | Mar 29 | Jan 4 – Jan 18 | Mar 1 – Mar 15 | — |
| 8b | Mar 16 | Dec 22 – Jan 5 | Feb 16 – Mar 2 | — |
| 9a | Mar 3 | Dec 9 – Dec 23 | Feb 3 – Feb 17 | — |
| 9b | Feb 20 | Nov 28 – Dec 12 | Jan 23 – Feb 6 | — |
| 10a | Mar 2 | Dec 8 – Dec 22 | Feb 2 – Feb 16 | — |
Zone rows use the median frost dates of all ZIP codes in that zone. Zones measure winter cold, not season length, so two places in the same zone can have frost dates weeks apart — use your ZIP code for real dates.
When to plant onions in major cities
| City | Median last frost | Start indoors | Transplant |
|---|---|---|---|
| Seattle, WA | Mar 13 | Dec 19 – Jan 2 | Feb 13 – Feb 27 |
| Portland, OR | Feb 25 | Dec 3 – Dec 17 | Jan 28 – Feb 11 |
| Salt Lake City, UT | Apr 25 | Jan 31 – Feb 14 | Mar 28 – Apr 11 |
| Denver, CO | Apr 30 | Feb 5 – Feb 19 | Apr 2 – Apr 16 |
| Minneapolis, MN | Apr 23 | Jan 29 – Feb 12 | Mar 26 – Apr 9 |
| Chicago, IL | Apr 10 | Jan 16 – Jan 30 | Mar 13 – Mar 27 |
| Detroit, MI | Apr 27 | Feb 2 – Feb 16 | Mar 30 – Apr 13 |
| Kansas City, MO | Apr 4 | Jan 10 – Jan 24 | Mar 7 – Mar 21 |
| Columbus, OH | Apr 20 | Jan 26 – Feb 9 | Mar 23 – Apr 6 |
| Boston, MA | Apr 4 | Jan 10 – Jan 24 | Mar 7 – Mar 21 |
| New York, NY | Mar 30 | Jan 5 – Jan 19 | Mar 2 – Mar 16 |
| Philadelphia, PA | Mar 30 | Jan 5 – Jan 19 | Mar 2 – Mar 16 |
| Washington, DC | Mar 29 | Jan 4 – Jan 18 | Mar 1 – Mar 15 |
| Charlotte, NC | Mar 30 | Jan 5 – Jan 19 | Mar 2 – Mar 16 |
| Nashville, TN | Apr 1 | Jan 7 – Jan 21 | Mar 4 – Mar 18 |
| Atlanta, GA | Mar 25 | Dec 31 – Jan 14 | Feb 25 – Mar 11 |
| Dallas, TX | Mar 2 | Dec 8 – Dec 22 | Feb 2 – Feb 16 |
Growing onions: quick facts
| Frost tolerance | Hardy: survives hard frosts, down to about 25°F or colder |
|---|---|
| Soil temperature | at least 35°F to germinate; 50–95°F is ideal |
| Planting depth | ¼–½ in (seed); sets 1 in |
| Spacing | 4–6 in |
| Germination | 7–14 days |
| Days to harvest | about 100 days from planting out |
Typical figures from university extension planting guides. Seed packets give the best numbers for a specific variety.