When to Plant Onion in Polk County, OR
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.
Polk County, Oregon is in USDA Zone 8a. The average last spring frost is April 10 and the first fall frost is October 31, giving you a growing season of approximately 204 days.
At an elevation of 331 feet, Polk County receives approximately 54.4 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. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Onion root diseases.
Polk County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.5
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 — Polk County, OR
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 6 | Mar 6 – Mar 20 |
| Transplant Outdoors | April 10 | Apr 10 – Apr 24 |
| Direct Sow | March 27 | Mar 27 – Apr 17 |
| Fall Sowing | August 22 | Aug 22 – Sep 5 |
| Harvest | July 10 | Jul 10 – Aug 28 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Fall Sowing |
| 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 8a
Growing Season
204 days
Growing Tips for Polk 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 Polk County, OR?
Polk County is in Zone 8a with an average last frost of April 10. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Polk County, OR?
Polk County, Oregon is in USDA Hardiness Zone 8a. The average last spring frost is April 10 and first fall frost is October 31.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Polk County gardeners in Zone 8a organize planting dates, track what's growing, and never miss a planting window.
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