When to Plant Onion in Fresno County, CA
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
Fresno County, California is in USDA Zone 9a. The average last spring frost is March 2 and the first fall frost is November 23, giving you a growing season of approximately 266 days.
At an elevation of 2,276 feet, Fresno County receives approximately 14.9 inches of rainfall annually with predominantly loam soil. Summer highs average 100°F, so Onion may need afternoon shade and extra watering during peak heat. With low rainfall, drip irrigation is essential for growing Onion successfully. Mulch heavily to conserve soil moisture.
Fresno County Soil Profile
Soil Type
Loam
Soil pH
6.5-7.5
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Onion Planting Timeline — Fresno County, CA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 2 | Feb 2 – Feb 16 |
| Transplant Outdoors | March 2 | Mar 2 – Mar 16 |
| Direct Sow | February 9 | Feb 9 – Mar 2 |
| Fall Sowing | September 28 | Sep 28 – Oct 12 |
| Harvest | June 1 | Jun 1 – Jul 20 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | — |
| May | — |
| June | Harvest |
| July | Harvest |
| August | — |
| September | Fall Sowing |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
USDA Zone
Zone 9a
Growing Season
266 days
Growing Tips for Fresno County
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Fresno County, CA?
Fresno County is in Zone 9a with an average last frost of March 2. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Fresno County, CA?
Fresno County, California is in USDA Hardiness Zone 9a. The average last spring frost is March 2 and first fall frost is November 23.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Fresno County gardeners in Zone 9a organize planting dates, track what's growing, and never miss a planting window.
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