Armoracia rusticana.© 2003 Eleanor Saulys. ct-botanical-society.org. (Accessed 4/2014).

Armoracia rusticana is a perennial herb to 1 m tall, erect, from a thick, woody, vertical tap root.

Leaves alternate, basal leaves to 30 cm long, base lobed, margin round-toothed (crenate), long-stalked, stem leaves narrow, smaller, short-stalked to stalkless, the lowest sometimes pinnately divided.

Flowers white, 4-parted, petals to 0.8 cm; May-July.

Fruit dry, hollow capsule, rounded to 0.6 cm, with elongate old stigma at tip, seeds rarely mature.

Wetland status: UPL.

Frequency in NYC: Very infrequent.

Origin: Europe, w. Asia.

Habitat: Escaped from cultivation into moist, open soil.

Notes: Leaves and roots contain mustard oil, a mixture of isothiocynates, pungent, irritating nitrogen-sulfur compounds of the form, CHx-N=C=S, poisonous to livestock (Kingsbury 1964).