When to plant Onion in Clinton County, IA
Plant Onion in Clinton County from April 3 to April 24 in spring. Clinton County sits in USDA Zone 5a, with last frost around April 17 and first frost on October 16. A second sowing from August 7 to August 21 extends the harvest into fall.
When to Plant Onion in Clinton 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.
Clinton County, Iowa is in USDA Zone 5a. The average last spring frost is April 17 and the first fall frost is October 16, giving you a growing season of approximately 182 days.
At an elevation of 964 feet, Clinton County receives approximately 38 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall.
Clinton County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Onion Planting Timeline — Clinton County, IA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 13 | Mar 13 – Mar 27 |
| Transplant Outdoors | April 17 | Apr 17 – May 1 |
| Direct Sow | April 3 | Apr 3 – Apr 24 |
| Harvest | July 17 | Jul 17 – Sep 4 |
| Fall Sowing | August 7 | Aug 7 – Aug 21 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors |
| 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
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5a
📆 Growing Season
182 days in Clinton County
Growing Tips for Clinton 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 Clinton County, IA?
Clinton County is in Zone 5a with an average last frost of April 17. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Clinton County, IA?
Clinton County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 17 and first fall frost is October 16.
When should I plant Onion in Clinton County, IA?
In Clinton County, IA, plant Onion after the last frost (around April 17) and before the first frost (around October 16). Best results when soil holds above 50°F.
What growing zone is Clinton County, IA for Onion?
Clinton County sits in USDA Zone 5a. Onion grows reliably in zones 3a through 10b, so it's a good fit here.
Can Onion grow in Clinton County's climate?
Yes — Onion grows well in Clinton County's temperate climate. Clinton County averages a 182-day frost-free season, with last frost around April 17 and first frost around October 16.
Your Clinton County Garden Planner — Free
A 22-page printable planner built for Clinton County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.