When to plant Onion in Washington County, MN
Washington County sits in USDA Zone 5a. Plant Onion between April 9 (after last frost on April 23) and April 30. A second sowing from July 31 to August 14 extends the harvest into fall.
When to Plant Onion in Washington County, MN
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.
Washington County, Minnesota is in USDA Zone 5a. The average last spring frost is April 23 and the first fall frost is October 9, giving you a growing season of approximately 169 days.
At an elevation of 832 feet, Washington County receives approximately 30.5 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Onion during the growing season.
Washington County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Onion Planting Timeline — Washington County, MN
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 19 | Mar 19 – Apr 2 |
| Transplant Outdoors | April 23 | Apr 23 – May 7 |
| Direct Sow | April 9 | Apr 9 – Apr 30 |
| Harvest | July 23 | Jul 23 – Sep 10 |
| 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 |
| 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
169 days in Washington County
Growing Tips for Washington 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 Washington County, MN?
Washington County is in Zone 5a with an average last frost of April 23. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, MN?
Washington County, Minnesota is in USDA Hardiness Zone 5a. The average last spring frost is April 23 and first fall frost is October 9.
When should I plant Onion in Washington County, MN?
In Washington County, MN, plant Onion after the last frost (around April 23) and before the first frost (around October 9). Best results when soil holds above 50°F.
What growing zone is Washington County, MN for Onion?
Washington 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 Washington County's climate?
Yes — Onion grows well in Washington County's temperate climate. Washington County averages a 169-day frost-free season, with last frost around April 23 and first frost around October 9.
Your Washington County Garden Planner — Free
A 22-page printable planner built for Washington 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.