Horseradish belongs in the perennial food garden. Once the plants are established, they can be harvested at any time of the year, and the flavour is particularly good in winter, when cold temperatures bring out a sweetness in the roots. Here’s our guide to how to grow horseradish from seeds:
Season & Zone
Season: Year round
Exposure: Full-sun to partial shade
Zone: 3 to 9
For first season harvests, start the seeds indoors in January to February and transplant out in April. The goal is to achieve large, fully established roots that can be divided and/or replanted. If time is not pressing, direct sow any time from March into summer. Optimal soil temperature: 7-23°C (45-75°F).
Sow seeds 5mm-1cm (¼-½”) deep in well cultivated, deep soiil. Seeds will sprout in 7-15 days, depending on conditions. Thin or transplant to 20cm (8″) apart in rows 40-50cm (16-20″) apart.
Ideal pH: 6.0-6.8. Well drained, warm soil in full sun is best. Raised beds help with both drainage and warmth. Use 1 cup of complete organic fertilizer for every 3m (10′) of row. Newly emerged leaves are edible, or should be left to mature if growing for the roots. The flower petals are also edible — flowers should be removed before they set seeds, as they will self-sow with enthusiasm.
For the leaves, harvest as needed, shortly after they emerge, before they become woody. For the roots, harvest November through March. The roots can also be lifted and stored for spring planting to keep the crop going from season to season.
Diseases & Pests
In our experience, insects do not cause problems for horseradish.
Horseradish is thought to repel aphids and whiteflies, blister beetles, potato beetles, and some varieties of caterpillar. Its flowers attract beneficial predatory hoverflies.
More on Companion Planting.