When to Plant Onion in Fayette County, IA
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.
Fayette County, Iowa is in USDA Zone 4b. The average last spring frost is May 5 and the first fall frost is October 5, giving you a growing season of approximately 153 days.
At an elevation of 1,228 feet, Fayette County receives approximately 41.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 81°F, so choose short-season varieties of Onion to ensure they mature before fall.
Fayette County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.8
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
Onion Planting Timeline — Fayette County, IA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 24 | Mar 24 – Apr 7 |
| Transplant Outdoors | May 5 | May 5 – May 19 |
| Direct Sow | April 28 | Apr 28 – May 19 |
| Fall Sowing | July 13 | Jul 13 – Jul 27 |
| Harvest | August 4 | Aug 4 – Sep 22 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing |
| August | Harvest |
| September | Harvest |
| October | — |
| 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 4b
Growing Season
153 days
Growing Tips for Fayette 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 Fayette County, IA?
Fayette County is in Zone 4b with an average last frost of May 5. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Fayette County, IA?
Fayette County, Iowa is in USDA Hardiness Zone 4b. The average last spring frost is May 5 and first fall frost is October 5.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Fayette County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.
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