When to Plant Tomatoes in Zone 9

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GardenSays

Start tomato seeds indoors Dec 31 – Jan 14, transplant outside Mar 4 – Mar 11.

Start seeds indoors: Dec 31 – Jan 14
Transplant outside: Mar 4 – Mar 11
Last frost (typ.): Feb 25

In USDA zone 9, the typical last frost lands around Feb 25. Working back 6-8 weeks gives you a seed-starting window of Dec 31 – Jan 14 indoors. Tomatoes are killed by frost, so wait until Mar 4-Mar 11 — after frost danger AND once soil hits ~60°F.

That leaves roughly 265 days of growing season before the typical first fall frost (Dec 1) — enough for most varieties. In a short-season area, favor early-maturing varieties (check the days-to-maturity on the tag).

⚠ This year's transplant window (Mar 4 – Mar 11) has passed — dates shown are for planning next season.

Why

✓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 frostFeb 25
USDA zone 9: typical (50% probability) last 32°F frost — zone-level estimate; a city-level lookup is more precise
Our estimate, derived from the cited guidance.
2. Seed starting windowDec 31 – Jan 14
Tomato: start indoors 6-8 weeks before the last frost (Feb 25)
3. Transplant windowMar 4 – Mar 11
Tomato is frost-tender: go out 7-14 days after the last frost, once soil reaches 60°F
4. First fall frostDec 1
USDA zone 9: 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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