How to Start Horseradish From Seed
Horseradish is usually propagated from root pieces, called sets, because seed-grown plants vary and take longer to form good roots. Start from seed only if you want to grow a less predictable, long-term crop.
Start indoors or direct sow?
Direct sow in a permanent bed when possible, since horseradish develops a deep root and is easiest to manage without moving it. Seedlings can be started indoors and transplanted young, but root sets are the usual and more reliable planting method.
When to start Horseradish seeds
For an indoor experiment, sow 6 to 8 weeks before the last spring frost. Direct sow outdoors 2 to 3 weeks before the last frost, once the soil can be worked.
How to sow the seeds
Sow seeds about 1/4 inch deep in a sterile seed-starting mix. Use deep cells or small pots with drainage, and keep indoor containers in a bright location after seedlings emerge.
Germination
Seeds commonly germinate in about 7 to 14 days. Keep the mix evenly moist, not saturated, at roughly 65 to 75 F.
Seedling care
Give seedlings strong light for 14 to 16 hours daily if grown indoors, and water when the surface begins to dry. Provide airflow, use clean containers, and avoid overwatering to reduce damping off; thin to one seedling per cell.
Transplanting & hardening off
Harden seedlings off for 7 to 10 days before planting them outside after the soil is workable and severe freezes have passed. Plant carefully with the root ball intact in a deep, loose bed, spacing plants about 18 to 24 inches apart.
Tips
Choose a contained bed or large bottomless barrier, because even small root pieces can regrow. Harvesting or digging in the same area can spread the plant.
General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.