How to Grow Horseradish
Plant horseradish in a well-prepared, weed-free bed. Give this hardy perennial plenty of space in your garden bed as it spreads readily. Place the root pieces at a 45-degree angle in the soil with the flat (larger) end up and the slanted end down. The flat end should be one to two inches below the soil surface. Five to ten plants are usually sufficient for a home garden.
Keep soil moist throughout the establishment period. Irrigate through the growing season, but take care not to overwater.
Horseradish does not need a lot of fertilization. Fertilize in spring with five pounds of 10-10-10 per 100 square feet.
It is best if you don’t harvest the first year to allow for plants to get well established. In the subsequent years, you may harvest horseradish roots anytime from midsummer on, but for the best flavor, wait until late fall or until after the first frosts when the leaves have died back. Dig or loosen the soil around the roots and pull them out of the soil. Take the large, main root and as much of the secondary root system as possible. Wash and dry the roots. Use the largest pieces for your recipe. Smaller, side roots that are ¾ inch in diameter and about eight inches or longer can be replanted in a new bed. They will provide your next year’s crop. If not harvested, the roots will need to be divided every year or two.