Last revised February 11, 2010
Horseradish is grown on only about 3000 acres in the U.S. Most of it comes from California, New Jersey, Virginia, Illinois and Wisconsin. An explanation of how the name came into being was adapted from "Illinois Horseradish...A Natural Condiment", University of Illinois Circular 1084:
The name "horseradish" is thought to have come from an English adaptation of its German name. Germans called the plant "meerrettich" (meaning "sea radish") because it grew wild in European coastal areas. The German word meer (sea) sounds like "mare" in English. Perhaps "mareradish" became "horseradish". The word "horseradish" first appeared in print in 1597 in John Gerarde's English herbal on medicinal plants.
A totally different plant (Wasabi japonica) is used to produce a product called Japanese Horseradish or wasabi. It is propagated from crown sprouts, rhizomes, or less commonly from tissue-cultured plants and from seed. It is prized by Orientals as a flavoring for a number of foods. Although uniquely different in flavor from horseradish, it also has many similar flavor characteristics.
Wasabi is an aquatic plant grown in cool, continuously running streams, requiring much hand labor. There have been recent efforts to grow this plant in rice paddies and in hydroponic greenhouses for the harvest of leaf petioles for the processing market. A new variety called Wasabi Tainung No. 1, widely adapted and reportedly tolerant to a number of important diseases, was developed at the Ali-san Chiayi Experiment Station and released in 1990 to growers in Taiwan by the Taiwan Agricultural Research Institute.
Because of the difficulty in producing wasabi, and the demand for it, a substitute has been developed using American horseradish to which synthetic flavor compounds and the appropriate green food color have been added. Both wasabi and the substitute product are marketed as a canned dry powder or frozen or fresh paste. In Japan, the fleshy plant stem or leaf petioles of wasabi are also sold fresh in produce markets.
The following describes only production practices for horseradish common in the U.S.
Horseradish is divided into two general types, "common" and "Bohemian". Maliner Kren is a "Bohemian" type from which many local selections have been made. Improved Bohemian and Bohemian form the basis of the current industry. "Common" types have broad crinkled leaves and are considered to have superior quality, while "Bohemian" types have narrow smooth leaves, somewhat lower quality, but better disease resistance. Obtaining adequate quantities of quality planting stock of the right variety is a major concern in horseradish production!
Use planting stock from root cuttings that have been trimmed from the crop's main roots at harvest. Use root pieces with a diameter of 3/8 to 3/4 inches in diameter. Cut root pieces 8-12 inches long leaving a square cut at the top, and tapered cut at the bottom, so those planting will orient the root properly in the ground. Space rows 30-36 inches apart with in-row spacing of 15-24 inches. About 8700-9700 root cuttings will be required per acre.
Horseradish plants may be produced through tissue culture. Although more expensive, rapid increase of the desired planting material via tissue culture may be possible by contracting with plant propagators having tissue culture capabilities.
Use deep loam or sandy loam soil types that have good drainage. It is desirable to have a fair amount of organic matter in the soil as well. Shallow soils over hard subsoils are not suited for good production.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
The following are general recommendations. It is advisable to have a soil test done on each field to be planted. Fields should be limed to a pH of 6.0-6.5. Manure may be plowed under at 12-20 tons/acre in the fall.
Nitrogen: 100-200 (N) lb/acre depending on soil type.
Phosphorus: 100-150 (P2O5) lb/acre
Potassium: 100-150 (K2O) lb/acre
Boron: 2-3 (B) lb/acre
Sulfur: 30-50 (S) lb/acre
The root cuttings should be about l/2 to 3/4 inches in diameter and from 8-14 inches long. These should have been cut with a slanting cut on the lower end and a square cut at the top in order to determine the proper root placement in the soil. Plant roots as early in the spring as ground can be prepared, usually in early April. About a year is required to produce a crop. Since fields may be harvested in fall or spring, the spring harvest usually provides planting stock for planting. Under conditions where planting stock is available, and roots have time to get established, fall planting may also be feasible.
Roots may be placed in the soil either by transplanter or by hand. Transplanters might need some modification to work most efficiently. The transplanting operation should leave the root at an angle of about 45 degrees in the soil. This is very important for vigorous establishment and growth.
For hand planting, furrows should be made that are 3-5 inches deep. Roots are then dropped into the furrow making sure that all the tops are pointing in one direction, and the roots at a 45 degree angle. Then push some soil over the lower end of the root and firm it with the foot to hold it in place. A cultivator can be used to finish filling in the trench and covering the roots.
Some growers set the root so that several inches remain above the level soil surface. Then the roots are covered by forming ridges in the rows with disk hillers. This ridging also benefits the harvesting operation.
Whether roots are laid in trenches or placed at an angle in the soil, it would be desirable to plant two or four rows together in the same direction. This allows cultivation of the rows in the direction that the roots are set rather than against them.
Although irrigation early in the growing season is not required, greater yields will be obtained if horseradish is irrigated during dry periods in August and September. The benefits of irrigation will be greater on lighter soils where crops are more subject to moisture stress.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
HARVESTING, HANDLING, AND STORAGE
Approximate yields range from 7,000 to 8,000 lb/A. Horseradish makes its greatest growth in late summer and early fall. Harvest is usually delayed till October or early November for best yield. Fields may be harvested in fall or spring.
Harvesting is usually not started until a frost has killed off the tops. If harvesting is done before that, tops should be removed with a rotary cutter as close to the soil surface as possible. Allow several days between leaf removal and harvest. If bad weather prevents fall harvest, the roots can be harvested the following spring.
Harvest is usually done by using a modified 1 or 2 row potato harvester. It is important to set the harvester deep to allow maximum recovery of roots and also to reduce the number of volunteer plants that grow as weeds in subsequent years.
Before the roots are sent to the processor, small roots must be removed as the planting stock for the next season. The small roots selected to be stripped from the large roots should be about 0.5 in. in diameter and 10-14 inches long, and free from injury. The bottom of each root should be given a slanting cut and the top a straight cut to indicate root position at planting. Store the roots and planting stock at low temperatures and high humidity with good air circulation.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Horseradish should keep satisfactorily for up to 10-12 months at 30 to 32 F, relative humidity of 90-95%. A high relative humidity is essential for minimum deterioration during storage. Perforated plastic bags or bin liners can aid in maintaining the high humidity. Roots should be kept in the dark because they can become green when exposed to light. Roots dug when the plant is actively growing do not keep as well as those conditioned by cold weather before they are dug. Frequent inspection is storage is advisable. Horseradish can also be stored over winter in cool cellars or in outdoor pits or trenches.
The requirements for marketing the roots are: A well-flavored root, reasonably straight, without side shoots, and no mechanical or decay damage. The roots should be at least 8 in. long with a diameter of not less than 0.75 in.
Horseradish is commonly packaged in 60-lb sacks, 50-lb sacks, 5-lb cello packages, or delivered in bulk for processing.