Oekon. Fl. Wetterau 2: 426. 1800.
Roots fusiform or cylindrical, fleshy or woody. Stems 5–12 (–20) dm. Basal leaves: petiole to 60 cm (broadly expanded basally); blade broadly oblong, oblong-lanceolate, or ovate, (10–) 20–45 (–60) cm × (30–) 50–120 (–170) mm, margins usually coarsely crenate, rarely pinnatifid. Cauline leaves: proximal shortly petiolate, blade oblong to linear-oblong (lobed), smaller than basal, margins pinnatifid or pinnatisect; distal sessile or shortly petiolate, blade linear to linear-lanceolate, base cuneate or attenuate, margins usually serrate or crenate, rarely entire. Racemes to 40 cm. Fruiting pedicels ascending, 8–20 mm. Flowers: sepals 2–4 mm; petals obovate or oblanceolate, 5–7 (–8) mm, claw to 1.5 mm; filaments 1–2.5 mm; anthers 0.5–0.8 mm. Fruits (rarely produced), 4–6 mm; style obsolete or to 0.5 mm; stigma well-developed. Seeds compressed (often not produced, rarely to 4 per locule). 2n = 32.
Phenology: Flowering Mar–Jul.
Habitat: Fields, moist stream banks, roadsides, ditches, disturbed sites, open woods, along railroads, shallow ponds, marshes, waste places
Elevation: 0-1100 m
Introduced; B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo., Europe, Asia, also nearly worldwide
Armoracia rusticana has been widely cultivated for about 2000 years for its fleshy roots that are grated to produce the pungent horseradish sauce. The plant is also a noxious weed that is very difficult to eradicate, even tiny root fragments are capable of regenerating new plants.
"elongated" is not a number."thick" is not a number."dm" is not declared as a valid unit of measurement for this property.