When to plant · 12 cities · zones 6b–9a
When to plant onions in Oregon
Start Spanish Onion seeds indoors around Jan 17 and transplant around Mar 14 — the Oregon statewide median, counted from a last spring frost of Apr 11 across 398 ZIP codes and 155 NOAA stations.
The rule: Twelve weeks indoors, the earliest sowing on the calendar, then transplant about four weeks before the last frost.
Oregon onions, by step
Statewide median last frost Apr 11, first fall frost Oct 30, 2027 season. Each cultivar's own indoor lead time and days to maturity, same engine as the Plan Builder.
| Cultivar | Start indoors | Plant out | First harvest | Days |
|---|---|---|---|---|
| Spanish OnionYellow Sweet Spanish (long-day) | Jan 17 | Mar 14 | Jul 2 | 110 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost. Statewide dates are the ZIP-weighted median of every NOAA 1991–2020 station Oregon's ZIP codes resolve to; 30 of 428 ZIPs have no datable freeze and are left out.
Onions in Oregon, city by city
Spanish Onion, scheduled from each city's nearest NOAA station — the same dates as its frost page.
| City | Last frost | Start indoors | Plant out | First harvest |
|---|---|---|---|---|
| Portlandzone 8b | Feb 25 | Dec 3 | Jan 28 | May 18 |
| Salemzone 8b | Apr 3 | Jan 9 | Mar 6 | Jun 24 |
| Eugenezone 8b | Apr 11 | Jan 17 | Mar 14 | Jul 2 |
| Greshamzone 9a | Mar 16 | Dec 22 | Feb 16 | Jun 6 |
| Hillsborozone 8b | Apr 16 | Jan 22 | Mar 19 | Jul 7 |
| Bendzone 6b | Jun 6 | Mar 14 | May 9 | Aug 27 |
| Beavertonzone 9a | Feb 11 | Nov 19 | Jan 14 | May 4 |
| Medfordzone 8b | Apr 8 | Jan 14 | Mar 11 | Jun 29 |
| Corvalliszone 8b | Apr 17 | Jan 23 | Mar 20 | Jul 8 |
| Springfieldzone 8b | Apr 11 | Jan 17 | Mar 14 | Jul 2 |
| Tigardzone 9a | Apr 1 | Jan 7 | Mar 4 | Jun 22 |
| Albanyzone 8b | Apr 17 | Jan 23 | Mar 20 | Jul 8 |
What these onions become
What Oregon onions need
Yellow Sweet Spanish Onion Seed
A long-day storage onion with enough sugar to sweat down without scorching. The aromatic base under every tomato sauce on this site.
Organic Seed Starter Potting MixMust have
Seed-starting mix is not potting soil with a nicer label — it is finer, lighter, and low in nutrients on purpose, because a seedling's first roots want air and moisture, not fertiliser.
72-Cell Trays with 1020 Bottoms, 5-PackMust have
The cheap black nursery trays crack after one season and flex enough to break roots when you lift them. These do not. Over five seasons the price per use is lower than the throwaways.
T8 Full-Spectrum Grow Lights, 1 ft 4-packMust have
A south window in March delivers a fraction of the light a pepper seedling needs, and the plant tells you by stretching. Two inches of LED above the canopy for 16 hours a day fixes it permanently.
Rapitest Soil Test Kit
In-ground growers are guessing until they test. pH outside 6.0–6.8 locks nutrients out no matter how much fertiliser you add, and no amount of feeding fixes that.
Pure Organic Worm Castings, 15 lb
Not a fertiliser so much as a soil-biology inoculant with a mild nutrient charge. A cup in each planting hole is a cheap, unglamorous improvement you can measure by August.
Garden Harvest Basket with Tool Caddy
A harvest basket that doubles as a colander means the hose rinse happens in the garden, and the dirt stays outside. On a 20-pound tomato day that is a genuine time saving.
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Onions in Oregon: questions
When should I plant onions in Oregon?
Transplant around Mar 14 at the statewide median; across the state that date runs from Feb 9 in the warmest tenth of Oregon's ZIP codes to Apr 29 in the coldest. To cut the freeze risk to one year in ten, count from May 3 instead of the median last frost. Use the city table for your own town.
When do I start onions seeds indoors in Oregon?
Around Jan 17 for Spanish Onion: 12 weeks before the statewide median last frost, on soil held at 65–75 °F.
When is the last frost in Oregon?
The ZIP-weighted median of NOAA 1991–2020 station medians is Apr 11. In the warmest tenth of Oregon's ZIP codes the median last frost falls on or before Mar 9; in the coldest tenth, on or after May 27.
When will Oregon onions be ready to harvest?
Spanish Onion planted on the statewide date is ready around Jul 2: 110 days from transplant.
Which onions grow in Oregon?
Spanish Onion is a long-day onion, correct above roughly 36° N. Every Oregon city listed here is north of that line.
More for Oregon
- When to plant tomatoes
- When to plant peppers
- When to plant tomatillos
- When to plant basil
- When to plant cilantro
- When to plant carrots
- When to plant mustard greens
Onions in every state → · Oregon frost dates → · How frost-date math works →