Onion
Vegetables · Sow outdoors or set out
Onion planting dates
At usual odds in 2026: Apr 6 – May 11.
The guide's rule Sets and seeds: 3 weeks before last frost to 2 weeks after last frost.
Frost odds · chance of a freezing night after your spring date
The 2026 season
Start indoors Plant out / sow Frost risk
At all three odds
| Frost odds | Start indoors | Plant / sow |
|---|---|---|
| Bold (1 in 2) | Feb 2 – Apr 6 | Mar 30 – May 4 |
| Usual (3 in 10) | Feb 9 – Apr 13 | Apr 6 – May 11 |
| Careful (1 in 10) | Feb 17 – Apr 21 | Apr 14 – May 19 |
- Days to first harvest
- 40-70 from sets
- How it goes in
- Sow outdoors or set out 4-8 weeks indoors to transplant size
- Frost
- Frost-hardy Takes light frost.
- Soil to germinate
- 50-80°F
Plan it in your Garden Book
The book checks your date against the window and tells you when the first harvest could come.
Plus Free Garden Books hold 8 plantings a season; Seed Clock Plus holds 120: $1.95/month or $19.50/year. Free during preview What Plus adds
Source: Montana State University Extension, MontGuide MT199308AG, "Can I Grow That Here? Vegetable Seed and Transplant Schedules for Garden or Container" (reviewed August 2013), read with NOAA 1991-2020 freeze odds for Cleveland Hopkins. Wording ours; how we read the guide.