2026 Planting Guide
Fall cropWhen to Plant Onions in California
Complete guide to growing onions in California with optimal planting dates, recommended varieties, soil requirements, pest management, and harvest timing. Data sourced from USDA and state extension services.
Monthly Planting Calendar
Visual overview of the onions growing season in California. Red diamond markers indicate frost date boundaries.
Quick Facts
Min. Soil Temp
50°F (10°C) minimum
Growing Period
90-150 days
From planting to harvest
Last Spring Frost
February 15
Wait until after this date
First Fall Frost
December 1
Harvest before this date
Monthly Task Timeline
Month-by-month guide for managing onions in California.
January
PlantPrepare soil, apply starter fertilizer, and sow seeds at recommended depth and spacing.
February - April
Grow & MonitorIrrigate as needed, scout for pests, apply side-dress fertilizer, and manage weeds.
May - August
HarvestCheck maturity indicators, schedule equipment, harvest at optimal moisture content.
September - December
PlantPrepare soil, apply starter fertilizer, and sow seeds at recommended depth and spacing.
Best Onions Varieties for California
These varieties have proven performance in California's climate and soil conditions. Always source certified seed from reputable dealers.
| # | Variety | Best For |
|---|---|---|
| 1 | Yellow Granex | California climate |
| 2 | Stockton Red | California climate |
| 3 | White Sweet Spanish | California climate |
| 4 | Candy | California climate |
Growing Tips for California
Region-specific advice from agricultural extension services and experienced California farmers.
Imperial Valley and San Joaquin Valley are primary zones
Direct seeded or transplanted
Drip irrigation with plastic mulch standard
Pest & Disease Watch
Monitor for these threats throughout the growing season. Integrated Pest Management (IPM) is recommended.
Thrips
Scout regularly and use integrated pest management
Onion maggot
Scout regularly and use integrated pest management
Purple blotch
Scout regularly and use integrated pest management
Downy mildew
Scout regularly and use integrated pest management
Stemphylium blight
Scout regularly and use integrated pest management
Companion Planting
These plants grow well alongside onions, improving pest control, pollination, and nutrient availability.
Frost Dates
Last Spring Frost
February 15
Wait until after this date before planting frost-sensitive crops outdoors.
First Fall Frost
December 1
Plan to complete harvest of warm-season crops before this date arrives.
Frequently Asked Questions
When is the best time to plant onions in California?
The optimal planting window for onions in California is September 15 to January 31. Soil temperature should reach at least 50°F (10°C) minimum before planting. The total growing period is 90-150 days.
What varieties of onions grow best in California?
The best varieties for California include Yellow Granex, Stockton Red, White Sweet Spanish, Candy. These varieties are adapted to local climate and soil conditions and have proven performance records.
When can I harvest onions in California?
The harvest window for onions in California is typically May 1 to August 31. The crop takes 90-150 days from planting to reach maturity.
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Data Sources
Data sourced from USDA NASS Crop Planting Dates, California Cooperative Extension Service, and NOAA frost date records. Last updated: March 2026.
Planting dates are averages and may vary by county, elevation, and local microclimate. Always consult your local extension office for the most precise recommendations.