Start indoors or direct sow?

Start indoors and transplant in short-season areas, or direct sow in warm spring soil. The seedlings transplant reasonably well when moved young, but direct sowing is simple where summers are long.

When to start Shiso seeds

For indoor plants, sow about 4 to 6 weeks before the average last spring frost. Direct sow after the last frost, once soil has warmed to about 65 F or more.

How to sow the seeds

Sow seeds 1/8 inch deep in a sterile seed-starting mix, using cell packs or small pots with drainage. Keep indoor trays warm and place seedlings under bright grow lights as soon as they emerge.

Germination

Germination commonly takes about 7 to 21 days. Keep the mix evenly moist but not saturated, with soil around 70 to 75 F for best results.

Seedling care

Give seedlings 14 to 16 hours of strong light daily and water when the surface of the mix begins to dry. Provide airflow, use clean containers and mix, and avoid overwatering to limit damping off; thin direct-sown plants to about 12 to 18 inches apart.

Transplanting & hardening off

Harden seedlings off over 7 to 10 days after frost danger has passed and nighttime temperatures are consistently mild. Transplant at the same depth, space plants about 12 to 18 inches apart, and water them in well.

Tips

Shiso can self-sow, so remove flower spikes if you want to limit volunteer seedlings. Seeds may germinate unevenly, so keep the tray labeled and give it the full three weeks before giving up.

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