When to plant Onion in Dubuque County, IA
For Onion in Dubuque County, the safe spring window opens around April 15 and closes around May 6. Last expected frost is April 29, first fall frost October 9, giving a 163-day growing season. A second sowing from July 31 to August 14 extends the harvest into fall.
When to Plant Onion in Dubuque 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.
Dubuque County, Iowa is in USDA Zone 5a. The average last spring frost is April 29 and the first fall frost is October 9, giving you a growing season of approximately 163 days.
At an elevation of 1,243 feet, Dubuque County receives approximately 36.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Onion to ensure they mature before fall.
Dubuque County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Onion Planting Timeline — Dubuque County, IA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 25 | Mar 25 – Apr 8 |
| Transplant Outdoors | April 29 | Apr 29 – May 13 |
| Direct Sow | April 15 | Apr 15 – May 6 |
| Harvest | July 29 | Jul 29 – Sep 16 |
| Fall Sowing | July 31 | Jul 31 – Aug 14 |
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 | Fall Sowing 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
163 days in Dubuque County
Growing Tips for Dubuque 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 Dubuque County, IA?
Dubuque County is in Zone 5a with an average last frost of April 29. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Dubuque County, IA?
Dubuque County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 29 and first fall frost is October 9.
When should I plant Onion in Dubuque County, IA?
In Dubuque County, IA, plant Onion after the last frost (around April 29) and before the first frost (around October 9). Best results when soil holds above 50°F.
What growing zone is Dubuque County, IA for Onion?
Dubuque 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 Dubuque County's climate?
Yes — Onion grows well in Dubuque County's temperate climate. Dubuque County averages a 163-day frost-free season, with last frost around April 29 and first frost around October 9.
Your Dubuque County Garden Planner — Free
A 22-page printable planner built for Dubuque 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.