Start indoors or direct sow?

Start indoors and transplant after frost danger has passed, because tomatillos need warm soil and a long growing season. Direct sowing works only in long, reliably warm summers and usually delays harvest.

When to start Tomatillos seeds

Sow indoors 6 to 8 weeks before the average last spring frost. Transplant 1 to 2 weeks after that date, once nighttime temperatures are regularly above about 50 F and the soil has warmed.

How to sow the seeds

Sow seeds 1/4 inch deep in sterile seed-starting mix in cells at least 1 1/2 to 2 inches wide. Use a heat mat if the room is cool, then pot seedlings up if they outgrow their cells before planting time.

Germination

Germination commonly takes 5 to 10 days in soil around 70 to 85 F. Keep the mix consistently moist but never saturated.

Seedling care

Provide very bright light, ideally a grow light kept close above seedlings, and water at the base as needed. Use gentle airflow, clean containers, and good drainage to limit damping off, then thin to one strong plant per cell.

Transplanting & hardening off

Harden plants off for 7 to 10 days before planting them in full sun after frost risk has passed. Plant them at the same depth or slightly deeper than their pots, space them about 2 to 3 feet apart, and provide a cage or stake early.

Tips

Do not rush plants into cold soil, because cool conditions can stall growth. Label varieties carefully if saving seed, since nearby tomatillo varieties can cross-pollinate.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.