When to Plant Onion in Mono 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.
Mono County, California is in USDA Zone 5b. The average last spring frost is June 18 and the first fall frost is August 20, giving you a growing season of approximately 63 days.
At an elevation of 2,381 feet, Mono County receives approximately 13.3 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Onion successfully. Mulch heavily to conserve soil moisture.
Mono County Soil Profile
Soil Type
Loam
Soil pH
6-7.5
Drainage
Well Drained
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 | — | 2.7" | 0" | ❄️ Dormant |
| Feb | — | 3.1" | 0" | ❄️ Dormant |
| Mar | — | 1.9" | 0" | ❄️ Dormant |
| Apr | — | 1" | 0" | ❄️ Dormant |
| May | — | 0.3" | 0" | ❄️ Dormant |
| 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 | — | 0.2" | 0" | ❄️ Dormant |
| Oct | — | 0.6" | 0" | ❄️ Dormant |
| Nov | — | 1.1" | 0" | ❄️ Dormant |
| Dec | — | 2.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Jun–Aug in Mono County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Planting Timeline — Mono County, CA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | May 14 | May 14 – May 28 |
| Transplant Outdoors | June 18 | Jun 18 – Jul 2 |
| Direct Sow | June 4 | Jun 4 – Jun 25 |
| Harvest | September 17 | Sep 17 – Nov 5 |
| Fall Sowing | June 11 | Jun 11 – Jun 25 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Start Indoors |
| June | Transplant Outdoors Direct Sow Fall Sowing |
| July | Transplant Outdoors |
| August | — |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5b
📆 Growing Season
63 days in Mono County
Growing Tips for Mono 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
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Mono County, CA?
Mono County is in Zone 5b with an average last frost of June 18. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mono County, CA?
Mono County, California is in USDA Hardiness Zone 5b. The average last spring frost is June 18 and first fall frost is August 20.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Mono County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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