Start indoors or direct sow?

Direct sow radishes, since they develop quickly and do not benefit from indoor starting. Transplanting can check growth and reduce root quality.

When to start Radishes seeds

Sow spring radishes 2 to 4 weeks before the average last spring frost, then repeat every 7 to 10 days while weather stays cool. For fall harvests, sow about 4 to 8 weeks before the first expected fall frost, depending on the variety.

How to sow the seeds

Sow seeds 1/2 inch deep in loose, well-drained garden soil. Place seeds about 1 inch apart in rows or small blocks, then thin if plants become crowded.

Germination

Radishes often germinate in 3 to 7 days. Keep soil evenly moist, and aim for soil temperatures roughly between 45 and 85°F.

Seedling care

Provide full sun and steady watering, especially as roots begin to swell. Thin plants to 1 to 2 inches apart for small salad radishes, and give larger winter types the spacing listed on their seed packet.

Transplanting & hardening off

Direct sown crop, so transplanting is not recommended. Protect new seedlings from flea beetles with a lightweight row cover when needed.

Tips

Sow a short row at a time rather than planting all your seeds at once. Harvest promptly once roots reach usable size, because overmature radishes can become pithy or hot.

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