Seed Starting Calendar for Oregon

Count back from the median last frost where you garden. At Medford (Medford Rogue Vly Airport) that date is April 8, so for spring 2027 onions start indoors Dec 31 to Jan 14, peppers Feb 11 to Feb 25 and tomatoes Feb 18 to Mar 4. Across Oregon's 165 NOAA stations the median last frost runs from Feb 25 to Jun 8 for the middle 90 percent, so a garden near O O Rch starts later than one near Brookings 2 SE.

It depends on the station. The earliest median last spring freeze in Oregon is January 31 at Brookings 2 SE; the latest is June 11 at O O Rch. A median is a coin flip: at Medford the last 32°F freeze comes after April 8 in half of years, and has passed by April 30 in 9 of 10 years (NOAA 1991 to 2020 normals).

UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Medford is Apr 15 to Apr 22 in 2027. Tomatoes are frost tender, so the date to watch is April 30, when 9 of 10 springs at Medford have had their last 32°F night. Hardening off starts two weeks before setting out (Apr 1 to Apr 15).

Oregon State University Extension Service publishes planting months by region (Region 1: Coast, Astoria to Brookings, Region 2: Western valleys, Portland to Roseburg, Region 3: High elevations, mountains, and plateaus of central and eastern Oregon, Region 4: Columbia and Snake valleys, Hermiston, Pendleton, Ontario). For Region 1: Coast, Astoria to Brookings, tomatoes go in during May and June. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

Oregon State University Extension Service's Vegetable Gardening in Oregon puts it this way: "Table 1 shows approximate planting dates for each region. Adjust planting dates based on your particular locality and seasonal weather pattern." The guide is linked below with the date it was read (September 21, 2026).

UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Medford that is Feb 11 to Feb 25 for peppers.

About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.

Portland reaches its median last frost around Feb 25, Medford around Apr 8, Ontario and Hermiston in late April, and Bend in the high desert around Jun 6. Each station carries its own dates: Portland Feb 25 and Bend Jun 6 at the median.