When to Plant Tomatoes in Portland
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GardenSays
Start tomato seeds indoors Mar 15 – Mar 29; transplant once frost danger is past and soil has warmed to ~60°F — typically May 10 – May 31 here.
- Start seeds indoors
- Mar 15 – Mar 29
- Transplant outside
- May 10 – May 31
- Last frost (typ.)
- Apr 5
In Portland, OR, the typical last frost lands around Apr 5. Working back 6-8 weeks from transplant time gives you a seed-starting window of Mar 15 – Mar 29 indoors. Tomatoes are frost-tender, so wait for two conditions — frost danger past AND soil around 60°F — which here typically means May 10-May 31.
- This year's transplant window (May 10 – May 31) has passed — dates shown are for planning next season.
Do this this week
- 1.Passed for this season — plan next spring: start seeds indoors ~Mar 15 – Mar 29, transplant ~May 10 – May 31
Typical estimate · 3 verified sources · Checked 2026-07-15 · How we decide
Why
Portland, OR is a slow-warming spring climate: frost safety arrives around Apr 12, but soil and night temperatures lag several weeks behind — planting at the frost-safe date usually means stalled, purple-tinged plants. The May 10 – May 31 window is our estimate for when warmth actually arrives; a soil thermometer reading ~60°F is the real green light.
That leaves roughly 154 days of growing season before the typical first fall frost (Nov 1) — enough for most varieties. In a short-season area, favor early-maturing varieties (check the days-to-maturity on the tag).
- Frost kills tender seedlings outright, and cold soil stunts them even without frost — both dates matter.
- The 50% frost date is a planning midpoint: a late frost is still possible, so keep covers handy for the first two weeks.
When this doesn't apply
- Season extenders (row covers, walls of water, cold frames) let you plant 2-3 weeks earlier than these windows.
- Frost dates are area averages — low spots and valley floors run colder than the local average.
How this was calculated
- 1. Last spring frostApr 5Source guidance
Portland, OR: typical (50% probability) last 32°F frost
- 2. Seed starting windowMar 15 – Mar 29Calculated result
Tomato: start indoors 6-8 weeks before your typical transplant date
- 3. Frost-safe fromApr 12Calculated result
Portland, OR: frost danger typically passes after the last frost — but frost-safe is not warm enough here
- 4. Typical transplant windowMay 10 – May 31GardenSays estimate
Portland, OR has a long, slow-warming spring: soil (~60°F) and mild nights arrive ~4-6 weeks after frost safety — our estimate; a soil thermometer beats the calendar
- 5. First fall frostNov 1Source guidance
Portland, OR: typical first 32°F frost in fall — the season's endpoint
Data sources
- University of Minnesota Extension — Growing tomatoes in home gardens — Start tomato seeds indoors about 6 weeks before the last frost; transplant after all danger of frost, once soil has warmed. (checked 2026-07-15)
- NOAA NCEI — 1991-2020 U.S. Climate Normals (freeze date probabilities) (checked 2026-07-15)
- National Gardening Association — frost date lookup (checked 2026-07-15)
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People also ask
What is the last frost date in Portland?
Start tomato seeds indoors Mar 15 – Mar 29; transplant once frost danger is past and soil has warmed to ~60°F — typically May 10 – May 31 here. Calculate yours →
When should I start tomato seeds indoors?
Start tomato seeds indoors Mar 15 – Mar 29; transplant once frost danger is past and soil has warmed to ~60°F — typically May 10 – May 31 here. Calculate yours →
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