When to Plant Onions in California
In California, the time to plant onions outside runs from Dec 4 – Dec 18 in Fremont to Dec 3 – Dec 17 in Oxnard. In Los Angeles, it's Dec 5 – Dec 19. The average last spring frost differs by about 52 weeks across the state (Jan 1 in Fremont, Dec 31 in Oxnard), so use the dates for the town nearest you.
Onions are cold-hardy. Plant sets or transplants early so they grow leaves before long summer days trigger bulbing.
- Start indoors: 10–12 weeks before the last frost.
- Plant outside: 2–4 weeks before the last frost.
Onions planting dates in California by city
| City | Zone | Start indoors | Plant outside |
|---|---|---|---|
| Anaheim | 10a | Oct 13 – Oct 27 | Dec 8 – Dec 22 |
| Bakersfield | 9b | Nov 8 – Nov 22 | Jan 3 – Jan 17 |
| Chula Vista | 10b | Oct 14 – Oct 28 | Dec 9 – Dec 23 |
| Corona | 10a | Oct 25 – Nov 8 | Dec 20 – Jan 3 |
| Elk Grove | 9b | Nov 10 – Nov 24 | Jan 5 – Jan 19 |
| Escondido | 10a | Oct 10 – Oct 24 | Dec 5 – Dec 19 |
| Fontana | 10a | Oct 12 – Oct 26 | Dec 7 – Dec 21 |
| Fremont | 10a | Oct 9 – Oct 23 | Dec 4 – Dec 18 |
| Fresno | 9b | Oct 22 – Nov 5 | Dec 17 – Dec 31 |
| Garden Grove | 10b | Oct 13 – Oct 27 | Dec 8 – Dec 22 |
| Glendale | 10a | Oct 10 – Oct 24 | Dec 5 – Dec 19 |
| Hayward | 10a | Oct 10 – Oct 24 | Dec 5 – Dec 19 |
| Huntington Beach | 10b | Oct 13 – Oct 27 | Dec 8 – Dec 22 |
| Irvine | 10a | Oct 13 – Oct 27 | Dec 8 – Dec 22 |
| Lancaster | 8a | Jan 9 – Jan 23 | Mar 6 – Mar 20 |
| Long Beach | 10b | Oct 17 – Oct 31 | Dec 12 – Dec 26 |
| Los Angeles | 10b | Oct 10 – Oct 24 | Dec 5 – Dec 19 |
| Modesto | 9b | Nov 8 – Nov 22 | Jan 3 – Jan 17 |
| Moreno Valley | 9b | Nov 4 – Nov 18 | Dec 30 – Jan 13 |
| Oakland | 10a | Oct 15 – Oct 29 | Dec 10 – Dec 24 |
| Oceanside | 10a | Oct 31 – Nov 14 | Dec 26 – Jan 9 |
| Ontario | 10a | Oct 12 – Oct 26 | Dec 7 – Dec 21 |
| Oxnard | 10b | Oct 8 – Oct 22 | Dec 3 – Dec 17 |
| Palmdale | 8b | Dec 16 – Dec 30 | Feb 10 – Feb 24 |
| Pomona | 10a | Oct 16 – Oct 30 | Dec 11 – Dec 25 |
| Rancho Cucamonga | 10a | Oct 12 – Oct 26 | Dec 7 – Dec 21 |
| Riverside | 10a | Oct 17 – Oct 31 | Dec 12 – Dec 26 |
| Roseville | 9b | Nov 30 – Dec 14 | Jan 25 – Feb 8 |
| Sacramento | 9b | Oct 20 – Nov 3 | Dec 15 – Dec 29 |
| Salinas | 9b | Nov 6 – Nov 20 | Jan 1 – Jan 15 |
| San Bernardino | 10a | Nov 4 – Nov 18 | Dec 30 – Jan 13 |
| San Diego | 10b | Oct 14 – Oct 28 | Dec 9 – Dec 23 |
| San Francisco | 10a | Oct 7 – Oct 21 | Dec 2 – Dec 16 |
| San Jose | 9b | Oct 10 – Oct 24 | Dec 5 – Dec 19 |
| Santa Ana | 10b | Oct 13 – Oct 27 | Dec 8 – Dec 22 |
| Santa Clarita | 10a | Oct 16 – Oct 30 | Dec 11 – Dec 25 |
| Santa Rosa | 9a | Dec 3 – Dec 17 | Jan 28 – Feb 11 |
| Stockton | 9b | Nov 13 – Nov 27 | Jan 8 – Jan 22 |
| Sunnyvale | 10a | Oct 14 – Oct 28 | Dec 9 – Dec 23 |
| Visalia | 9b | Oct 31 – Nov 14 | Dec 26 – Jan 9 |
Calculated from each town's average (50%) frost dates, from the nearest NOAA station (1991–2020). Typical dates for the 2027 planting season, based on NOAA's 1991–2020 averages. They are long-term odds, not a forecast: always check your local forecast before planting. Zones: 2023 USDA Plant Hardiness Zone Map (USDA-ARS and Oregon State University). Not the official map; see planthardiness.ars.usda.gov.
See all frost dates in California, or the general guide to when to plant onions.
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