Quick planting window
| Start indoors | February to March |
|---|---|
| Transplant | March to April |
| Sow seeds | March to April |
| Estimated harvest | July to August |
| Risk | Low risk |
Month calendar
Scan the year by month to see seed starting, sowing, transplanting, and harvest timing.
Onion is a reasonable spring choice for Oregon if you adjust for your local microclimate.
Next: ZIP code personalization
This is a state-level planning window based on typical frost timing and crop rules. Use local Extension guidance or a ZIP code frost-date tool before planting.
Planning notes
Days to maturity
110
Covered states
Oregon
Frost window
April to May / October to November
Western Oregon and eastern Oregon planting windows can differ by weeks.
Onion growing notes
The calendar window is only the first step. These growing details affect survival, plant vigor, and harvest quality.
Sun
Full sun.
Soil
Loose, fertile soil with good drainage.
Spacing
4-6 inches for bulbs.
Container
Use wide containers at least 8-10 inches deep.
Watering
Keep evenly moist during bulb formation.
Common mistake
Choosing the wrong day-length onion type.
Beginner tip
Use sets or transplants if seed timing feels too long.
Month window table
| Crop | Spring transplant / sow | Spring harvest | Fall transplant / sow | Fall harvest |
|---|---|---|---|---|
| Onion | March to April | July to August | July to August | October to November |
Sources and limits
This page uses Oregon state-level frost windows, USDA zone ranges, and crop rules for planning. It does not replace local Extension or county-level guidance.
FAQ
When should I start onion seeds indoors in Oregon?
For spring, the indoor seed-starting window is about February to March. Move later if your local frost date is later than the state average.
When should I transplant onion in Oregon?
For spring, the transplant window is about March to April. Harden seedlings off before planting outside.
Can I sow onion outdoors in Oregon?
Yes. The spring outdoor sowing window is about March to April, assuming soil and night temperatures are suitable.
When can I harvest onion in Oregon?
Spring planting estimates a harvest around July to August; fall planting estimates about October to November. Variety and weather can shift this by several weeks.
Is onion risky in Oregon?
Onion is a reasonable spring choice for Oregon if you adjust for your local microclimate. For fall: Onion is a reasonable fall choice for Oregon if you adjust for your local microclimate.
Do local differences inside Oregon matter?
Western Oregon and eastern Oregon planting windows can differ by weeks. Treat this as a state-level starter window and confirm with a local Extension or frost-date tool before planting.
What growing details matter most for onion?
Full sun. Loose, fertile soil with good drainage. Common mistake: Choosing the wrong day-length onion type.
Is this ZIP-code accurate?
No. This page uses state-level windows; ZIP-code frost dates, USDA zone matching, and reminder calendars are planned for the next phase.