When to Start Tomatoes Indoors by Zone
Start tomato seeds indoors about 6 weeks before your last spring frost. Use your zone or My Garden frost date, then harden off before transplant.
Published · Reviewed by Blake Peavy
tomato seed starting zones winter
When to Start Tomatoes Indoors by Zone
Start tomato seed 6 weeks before your last spring frost, then harden off and transplant about a week after that frost, not on a national average date.
When to Start Tomatoes Indoors
Count 6 weeks before your last spring frost. Set that frost in My Garden (or pick a USDA zone with Find My Zone), then open the live seed-start calendar to turn the lead time into calendar dates for your yard.
Full plant detail: Tomato. Trays and light: How to start seeds indoors. Hub: Winter.
Zones 5-9 Example
The method is the same in every zone. Only your last frost changes.
- Set last spring frost in My Garden (or confirm zone with Find My Zone).
- Count back 6 weeks; that is your indoor sow date for tomato.
- Harden off for 14 days before you move plants to the bed (harden-off guide).
- Transplant about 7 days after last frost, when nights and soil are ready for a warm-season crop.
Do not paste a ZIP’s frost date from memory into a national chart. Use My Garden or Find My Zone, then the seed-start calendar.
Catalog Notes (Tomato)
Catalog soil about 60-85 F; sow 1/4 inch; about 75 days to harvest from transplant timing in the catalog. Warm soil and strong light after sprouting keep seedlings stocky. Skip a heat mat once they are up if they stretch.
Next Steps
Set last frost in My Garden, open seed starting, sow tomato 6 weeks out, harden 14 days, and transplant about 7 days after last frost. Pair with pepper trays (8 weeks before last frost) if you want both warm-season crops in the same spring wave.