Quick planting window
| Start indoors | January to February |
|---|---|
| Transplant | February to March |
| Sow seeds | February to March |
| Estimated harvest | June to July |
| Risk | Medium risk |
Month calendar
Scan the year by month to see seed starting, sowing, transplanting, and harvest timing.
Onion is a reasonable spring choice for California if you adjust for your local microclimate.
Next: ZIP code personalization
This is a state-level planning window based on typical frost timing and crop rules. Use local Extension guidance or a ZIP code frost-date tool before planting.
Planning notes
Days to maturity
110
Covered states
California
Frost window
February to April / November to December
Use this as a state-level starter window; coastal and inland gardens can differ by weeks.
Onion growing notes
The calendar window is only the first step. These growing details affect survival, plant vigor, and harvest quality.
Sun
Full sun.
Soil
Loose, fertile soil with good drainage.
Spacing
4-6 inches for bulbs.
Container
Use wide containers at least 8-10 inches deep.
Watering
Keep evenly moist during bulb formation.
Common mistake
Choosing the wrong day-length onion type.
Beginner tip
Use sets or transplants if seed timing feels too long.
Month window table
| Crop | Spring transplant / sow | Spring harvest | Fall transplant / sow | Fall harvest |
|---|---|---|---|---|
| Onion | February to March | June to July | August to September | November to December |
Sources and limits
This page uses California state-level frost windows, USDA zone ranges, and crop rules for planning. It does not replace local Extension or county-level guidance.
FAQ
When should I start onion seeds indoors in California?
For spring, the indoor seed-starting window is about January to February. Move later if your local frost date is later than the state average.
When should I transplant onion in California?
For spring, the transplant window is about February to March. Harden seedlings off before planting outside.
Can I sow onion outdoors in California?
Yes. The spring outdoor sowing window is about February to March, assuming soil and night temperatures are suitable.
When can I harvest onion in California?
Spring planting estimates a harvest around June to July; fall planting estimates about November to December. Variety and weather can shift this by several weeks.
Is onion risky in California?
Onion is a reasonable spring choice for California if you adjust for your local microclimate. For fall: Onion is a reasonable fall choice for California if you adjust for your local microclimate.
Do local differences inside California matter?
Use this as a state-level starter window; coastal and inland gardens can differ by weeks. Treat this as a state-level starter window and confirm with a local Extension or frost-date tool before planting.
What growing details matter most for onion?
Full sun. Loose, fertile soil with good drainage. Common mistake: Choosing the wrong day-length onion type.
Is this ZIP-code accurate?
No. This page uses state-level windows; ZIP-code frost dates, USDA zone matching, and reminder calendars are planned for the next phase.