When to plant Onion in Fresno County County,
In Fresno County County, plant Onion in spring between February 9 and March 2, once soil temps hold above 50°F. Fresno County County's last frost averages March 2, so aim for a steady week of warm soil before planting. For a fall crop, sow between September 28 and October 12 — roughly 120 days before the first frost on November 23.
When to Plant Onion in Fresno County, CA
This month in Fresno County, California
June rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Fresno County, California.
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Pick onion
Don't tug. Use scissors or pruners for clean cuts — torn stems invite disease.
Looking ahead to July
- First harvests: onion
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 9b. 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
Onion 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.
Soil Compatibility in Fresno County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.5–7.5) overlaps with Onion's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in Fresno County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.2%). Annual compost additions will help Onion.
How to Plant Onion
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Onion Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.8" | 0" | ❄️ Dormant |
| Feb | — | 3.3" | 0" | ❄️ Dormant |
| Mar | 4.3" | 2.3" | 2" | 💧 Light watering |
| Apr | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| May | 4.3" | 0.4" | 3.9" | 🚿 Regular watering |
| Jun | 4.3" | 0.1" | 4.2" | 🚿 Regular watering |
| Jul | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Aug | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Sep | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Oct | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Nov | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Dec | — | 2.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Fresno County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
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 |
| Harvest | June 1 | Jun 1 – Jul 20 |
| Fall Sowing | September 28 | Sep 28 – Oct 12 |
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
1"/week · 2-3 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 9b
📆 Growing Season
266 days in Fresno County
Growing Tips for Onion in Fresno County
Direct sow Onion outdoors after March 02 in Fresno County when soil has warmed and frost danger has passed.
With summer highs reaching 100°F in Fresno County, provide afternoon shade for Onion and water deeply in the morning.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
Fresno County receives only 15" of rain annually. Onion needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
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
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Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Fresno County, CA?
Fresno County is in Zone 9b 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 9b. The average last spring frost is March 2 and first fall frost is November 23.
When should I plant Onion in Fresno County County, ?
In Fresno County County, , plant Onion after the last frost (around March 2) and before the first frost (around November 23). Best results when soil holds above 50°F.
What growing zone is Fresno County County, for Onion?
Fresno County County sits in USDA Zone 9b. Onion grows reliably in zones 3a through 10b, so it's a good fit here.
Can Onion grow in Fresno County County's climate?
Yes — Onion grows well in Fresno County County's temperate climate. Fresno County County averages a 266-day frost-free season, with last frost around March 2 and first frost around November 23.
Your Fresno County Garden Planner — Free
A 22-page printable planner built for Fresno County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.