Armoracia sativa Bernhardi; Cochlearia armoracia Linnaeus; Nasturtium armoracia (Linnaeus) Fries; Rorippa armoracia (Linnaeus) A. S. Hitchcock; R. rusticana (G. Gaertner et al.) Godron.

Herbs with fusiform or cylindric, fleshy or woody roots. Stems 50-120(-200) cm tall. Basal leaves few; petiole to 60 cm, broadly expanded at base; leaf blade broadly oblong, oblong-lanceolate, or ovate, (10-)20-45(-60) × (3-)5-12(-17) cm, coarsely crenate or rarely pinnatifid. Lower and middle cauline leaves shortly petiolate, pinnatifid or pinnatisect, with oblong to linear-oblong lobes, smaller than basal leaves; upper cauline leaves sessile or shortly petiolate, linear to linear-lanceolate, base cuneate or attenuate, margin serrate, crenate, or rarely entire. Fruiting pedicels ascending, slender, 0.8-2 cm. Sepals ovate, 2-4 mm. Petals obovate or oblanceolate, 5-7(-8) mm; claw to 1.5 mm. Filaments 1-2.5 mm; anthers ovate, 0.5-0.8 mm. Ovules 8-12 per ovary. Mature fruit rarely produced, ovate, oblong, or suborbicular, 4-6 mm, few seeded; style obsolete or to 0.5 mm; stigma capitate, well developed. Seeds not seen. Fl. May-Jul. 2n = 32.

This species has been widely cultivated for some 2000 years for its fleshy roots, which are grated to produce the pungent horseradish sauce. The plant is also a weed that is very difficult to eradicate.

Cultivated and naturalized. Hebei, Heilongjiang, Jilin, Jiangsu, Liaoning [native to Europe; cultivated and naturalized elsewhere].