When to Plant Onion in Hardin County, OH
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.
Hardin County, Ohio is in USDA Zone 5b. The average last spring frost is April 26 and the first fall frost is October 20, giving you a growing season of approximately 177 days.
At an elevation of 935 feet, Hardin County receives approximately 30.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Onion during the growing season.
Hardin County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-6.8
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 — Hardin County, OH
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 22 | Mar 22 – Apr 5 |
| Transplant Outdoors | April 26 | Apr 26 – May 10 |
| Direct Sow | April 12 | Apr 12 – May 3 |
| Fall Sowing | August 11 | Aug 11 – Aug 25 |
| Harvest | July 26 | Jul 26 – Sep 13 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Fall Sowing 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 5b
Growing Season
177 days
Growing Tips for Hardin 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 Hardin County, OH?
Hardin County is in Zone 5b with an average last frost of April 26. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Hardin County, OH?
Hardin County, Ohio is in USDA Hardiness Zone 5b. The average last spring frost is April 26 and first fall frost is October 20.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Hardin County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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