The International Herb Association
Horseradish Herb of the Year™ 2011
International Herb Association Annual Publication
Horseradish in Bloom
photo by Elizabeth Wahle
(är-mör-ă-sĭ å rŭs-tĭ-kā-nå)
by Dr. Arthur O. Tucker
Family: Brassicaceae (Cruciferae)
Growth form: herbaceous perennial to 3 feet (1 m) or more
Hardiness: hardy to Maine (Zone 5)
Light: full sun
Water: moist but not constantly wet; can withstand some drought
Soil: average garden loam, pH 5.0 to 7.5, average 6.5
Propagation: divisions in early spring
Culinary use: sauces
Craft use: none
Landscape use: edges of borders
French: raifort, cran
German: Meerrettich, Kren
Italian: barbaforte, ramolaccio
Spanish: cochlearia, rábano rusticano
Japanese: seiyô wasabi
Arabic: fujl har
The Oracle at Delphi told Apollo that the radish was worth its weight in lead, the beet its weight in silver, and the horseradish its weight in gold. We don’t place such values on our plants today, but it’s hard to imagine Passover or hot roast beef without grated horseradish or cold seafood without cocktail sauce. Actually, horseradish only appeared in the Passover seder as maror in the Middle Ages (ca. 1215-1293) as Jews migrated north and eastward into colder climates. Horseradish provides a unique pungency different from that of black and red peppers, and the tall, broad leaves provide a textural contrast in the herb garden. Horseradish is also notably high in vitamin C and has anti-microbial activities to preserve meat. The root of horseradish is considered GRAS (Generally Recognized As Safe). Excessive doses of horseradish may lead to diarrhea or night sweats. One case of a heart attack has been recorded—the patient survived.
Once you grow horseradish, you’ll have this hardy perennial forever; even the smallest piece of horseradish root can grow a new plant, and whenever you are absolutely sure you’ve eradicated the horseradish bed this time, ‘lo and behold, it comes back. Superficially, horseradish resembles dock (Rumex spp.) with tall, stalked, slightly rumpled leaves.
Armoracia rusticana is one of three species in the genus, and may be an ancient hybrid of the other two species [A. lacustris (A. Gray) Al-Shehbaz & V. M. Bates and A. sisymbroides (DC.) Cajander]. All are smooth-leaved, perennial herbs with deep roots or rhizomes. The leaves are strap-like, either simple or dissected, and the flowers have four sepals and petals. Armoracia was the old Latin name for horseradish, while rusticana means rustic or of the country. The most primitive name seems to be chren, still common to Slavic languages and introduced into German and French dialects in variations. The German Meerrettich means literally sea-radish, as it sometimes naturalizes near seasides, and this name provided the later English name horseradish; meer seems to have been misunderstood by the English for mähre, an old horse, as if for the rankness and toughness of the roots. Some have made the apocryphal claim that horseradish, an herb of northern Europe, was cultivated prior to the Exodus of the Hebrew slaves (c. 1500 B.C.E.) from Egypt. In England, it only became popular in England in the late 1600s. From there it was transferred to North America.
In the past, commercial cultivation of horseradish in the U.S. was centered around Chicago; plants were brought to this area about 1856 by a German family named Sell, who gave roots to the Sass family. St. Louis was another commercial area, where horseradish has been grown since the 1890s. Today, the majority of horseradish is grown in Illinois, in the three counties closest to St. Louis.
In the United States, the commercial practice is to plant root cuttings 1/4 to 3/4 inches diameter and 8 to 14 inches long obliquely (an estimated 30° angle from horizontal is claimed to be best) to horizontal in shallow furrows with a large crown bud end resting slightly higher than the small or lateral root end. These are spaced 18 to 24 inches within the row and 30 to 36 inches between rows, and produce 8,900 to 9,700 plants per acre.
The sets are covered with 2 to 4 inches of soil; rolling then firms the soil. Soil should be pH 6.0 to 6.5; liberal applications of manure prior to planting are recommended. Addition of boron in boron-deficient soils will increase yields.
During growth, roots increase in diameter but little in length. Water stress produces bitter roots. To produce a high-quality marketable root, the roots are “lifted’’—the crown of the plant is pulled up and small lateral roots removed; then the root is replanted in its original position. Suggested times for lifting are when the largest leaves are 8-to 10-inches long and again about six weeks later. Lifted roots are more uniform and easier to clean, but the total yield is reduced by this procedure. Roots are dug either in fall or early spring. Harvested lateral roots are stored until spring for replanting the next crop.
If you grow horseradish in the home garden, early spring is the best time to plant the pencil-thin branches trimmed from larger roots. If you cannot plant the roots immediately, store them in plastic bags in the refrigerator until ready to plant. Choose a sunny location and work in plenty of rotted manure or compost to a depth of 10 inches. Depending upon your needs, plant one or two dozen roots, spacing them 12-to 18-inches apart. Set each piece so that the top is at ground level in a trench 3-to 5-inches deep. You may dig the roots as you need them, but after fall’s first heavy frost is when the flavor is at its peak. In areas where the ground does not freeze, you may harvest throughout the winter! Remove only the largest roots, leaving the small ones to survive another season; roots that are more than three years old should be discarded as too tough.
Horseradish is commercially dehydrated for export but tastes best when served fresh. The root may be shaved into curls to decorate and flavor beef. To prepare horseradish sauce, scrape the roots, grate (with good ventilation to avoid asphyxiation), and combine 1/2 cup white vinegar and 1/4 teaspoon salt with every cup of grated root. Bottle tightly and refrigerate for up to two months; grated red beets or various mustards may also be added. For longer storage, freeze the grated horseradish. Mix the sauce with ketchup to taste for shrimp cocktail sauce. If you harvest too many roots in the fall, store them in damp sand or in the refrigerator for grating later. Serve horseradish only in porcelain or glass, never silver, which blackens on contact with horseradish.
Numerous cultivars of horseradish exist, most sterile. Most of the U.S. cultivars today are essentially proprietary and jealously guarded. The most attractive for the garden is an unnamed variegated cultivar with white-splashed leaves; another unnamed cultivar has dark purple-green leaves. Both of these ornamental cultivars are difficult to locate and recommended only for the collector.
Cultivars may be grouped into one of three types: Type I has leaves with a heart-shaped base, Type III has leaves with a tapering base, while Type II is intermediate. Cultivars also vary as to whether the leaves are smooth or crinkled and on the yield per acre. Of more than thirty cultivars (and those that are proprietary), some of the more common ones and their chief characteristics are listed below.
Variation in leaves on the same plant has to do with genetics.
Photo by Susan Belsinger
Cultivar: ‘Big Top Western’
Leaf type: I, smooth
Yield per acre: 1.6 pounds per root with 4.65 tons per acre
Disease resistance: highly resistant to turnip mosaic 1, slightly resistant to white rust
Leaf type: I, smooth
Disease resistance: highly resistant to turnip mosaic 1, highly resistant to white rust
Cultivar: ‘Maliner Kren’ (“common’’)
Leaf type: III, crinkled
Yield/acre: 1.1 pounds per root with 2.79 tons per acre
Disease resistance: highly susceptible to turnip mosaic 1, highly susceptible to white rust
Leaf type: I, smooth
Yield/acre: 1.7 pounds per root with 4.81 tons/acre
Disease resistance: highly resistant to turnip mosaic 1, slightly resistant to white rust
Cabbageworms will feed on horseradish foliage, but these are easily controlled with strains of Bacillus thuringiensis. A worse problem is the imported crucifer weevil, Baris lepidii; the white grub-like larvae tunnel in the roots and reduce both quality and yield. Dipping the roots in a 0.1 to 5.0 percent permethrin solution for 30 to 120 minutes effectively kills this pest before planting. Horseradish flea beetle, Phyllotreta armoraciae, may also present a problem but is easily controlled with carbaryl (Sevin), an insecticide registered for horseradish. Horseradish may also be troubled by harlequin bugs and cabbage loopers.
White rust, caused by Albugo candida, is one of the most prevalent and destructive diseases. Bacterial leaf spot (Xanthomonas campestris var. armoraciae) is sometimes quite severe. Alternaria, a fungal disease, will cause lesions on older leaves similar to early blight of tomatoes. Some root rots also have been reported. Turnip mosaic 1 virus causes the formation of somewhat sunken black streaks in the leaf stalks and midribs that reach the crown as the season progresses, with blackening of the smaller leaf veins in some cultivars. Disease-free planting stock and wisely chosen cultivars are the best means of controlling these diseases.
In an ether extract of the ground root, the dominant components are 76 to 80 percent allyl isothiocyanate and 16 to 18 percent beta-phenylethyl isothiocyanate, or mustard oils, which irritate the ending of olfactory nerves and cause tears and salivation. Normally the mustard oils are bound with sugars as either sinigrin (allyl glucosinolate) or gluconasturtin (beta-phenylethyl glucosinolate) in the vacuoles of the cells, separated from a membrane-bound enzyme, myrosinase, but rupture of the cells allows hydrolysis of the sugar bonds by myrosinase, thereby releasing free isothiocyanates.
Botanical DescriptionA. rusticana P. Gaertn., B. Mey. & J. Scherbius, Oekon, Fl. Wetterau 2:426. 1800 (A. lapathifolia Gilib., Cochlearia armoracia L.).
Native country: Horseradish is probably native to southern Russia and eastern Ukraine but is cultivated widely in Europe and North America, where it has frequently escaped.
General habit: Flowering stems rise to 1 m or more.
Leaves: Basal leaves are 30 to 50 cm long, egg-shaped or oblong-egg-shaped, round-toothed, with a stalk to 30 cm.
Flowers: Flowers are yellow with petals 5 to mm long.
Fruits/Seeds: Fruits are dry globose or egg-shaped pockets 4 to 6 mm long with 4 to 6 seeds in each pocket.
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