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.
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.
Perennial herb to 1 m tall Stem: upright. Flowers: in branched clusters, pink or pinkish purple, 6 - 8 mm long. Petals four, tip rounded. Stamens six. Fruit: a pod, ascending, to 6 mm long, on a short stalk, egg-shaped, slightly round in cross-section, two-chambered. Lower leaves: long-stalked, 10 - 30 cm long, oblong, base heart-shaped, toothed. Upper leaves: alternate, stalkless or short-stalked, smaller than lower leaves, lance-shaped, toothed.
Similar species: Armoracia rusticana is the only representative of the genus Armoracia in the Chicago Region. Its height and large, oblong basal leaves are distinctive.
Flowering: May to early June
Habitat and ecology: Introduced from Europe. Often cultivated in home gardens. It readily grows from a root piece, and therefore escapes from cultivation as a result of earth-moving operations. Often found in moist soil, usually along ditches, roadsides, and stream banks. Has also been found growing along railroads.
Occurence in the Chicago region: non-native
Notes: The condiment Horseradish is made from the root.
Etymology: Armoracia is an old name for the genus. Rusticana means rustic (of the countryside).
Sep ascending, elliptic to obovate; pet white, obovate, gradually narrowed to the claw; short stamens subtended by a U - shaped gland; long stamens subtended by a small conic gland; anthers linear-oblong; ovary ovoid to ellipsoid; ovules numerous; style slender, stigma large, capitate; frs inflated, obovoid or ellipsoid, tipped with the slender style and conspicuous stigma; valves with an inconspicuous midnerve, otherwise nerveless; glabrous herbs. 4, Europe to Siberia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Much planted and used as a condiment. It has sparingly escaped from cultivation to ditches and banks of the smaller streams throughout the state. I once found it on the bank of a pond in a clearing. I have never seen it mature seed.
Indiana Coefficient of Conservatism: C = null, non-native