Plant 12- to 18-inch diameter horseradish roots in a trench that is approximately 6 inches deep. Hold the root at an angle so the crown is about 2 inches under the soil when you backfill the trench. Most families find that two horseradish starts are enough.
Horseradish is a perennial and can be invasive as the roots multiply and produce new shoots. One option to prevent it from spreading is to plant the shoots in containers that are a minimum of 30 inches deep.
When horseradish grows as a perennial, the roots tend to be smaller than those on plants in the grocery store. To produce the larger, more pungent roots, force the plant to grow as an annual. Remove any secondary shoots as soon as they break through the ground. Harvest the single large root at the end of the growing season.
Store the roots in the refrigerator in black plastic bags to prevent them from producing chlorophyll and turning green. To use the root, grate it directly into white wine or distilled white vinegar. Do not use cider vinegar as it discolors the horseradish. Only grate as much of the root as you are able to use within a couple of weeks, as it does not keep longer than this.