Armoracia rusticana P. Gaertner, B. Meyer & Scherbius, Brassicaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Evaluate; score: 1 (Hawaii-Pacific Weed Risk Assessment for Armoracia rusticana)

Other Latin names:  Armoracia lapathifolia Gilib. ex Usteri; Cochlearia armoracia L.; Nasturtium armoracia (L.) Fr.; Radicula armoracia (L.) B. L. Rob.; Rorippa armoracia (L.) Hitchc.

Common name(s): [more details]

English: horseradish

Habit:  herb

Description:  "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)&nbnsp;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 (Al-Shehbaz in JSTOR Plants)

Habitat/ecology:  "[Armoracia rusticana] grows along riverbanks and in other damp places. Ruderal plants are mainly confined to secondary anthropogenic habitats; for example, near arable land, in urban areas and in rural gardens." (IUCN Red List)

"Altitude range 0–1100 m" (Al-Shehbaz in JSTOR Plants)

Propagation:  ". . . [Armoracia rusticana]. . .is very difficult to eradicate, [sic] even tiny root fragments are capable of regenerating new plants." (Al-Shehbaz in JSTOR Plants)

Armoracia rusticana rarely produces fruits/seeds. (Al-Shehbaz in JSTOR Plants)

Native range:  "Native: Belarus; Estonia; Latvia; Lithuania; Moldova; Russian Federation (Central European Russia, East European Russia, Kaliningrad, North European Russia, Northwest European Russia, South European Russia); Ukraine (Krym, Ukraine (main part))" (IUCN Red List)

Impacts and invaded habitats:  "[Armoracia rusticana] is. . .a noxious weed that is very difficult to eradicate, [sic] even tiny root fragments are capable of regenerating new plants." (Al-Shehbaz in JSTOR Plants)

(no invaded habitats or impacts known by PIER; please let us know if you know of such information we should add here)

Presence:

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Asia Asia	Asia		Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414
British Columbia (province of Canada) Province of British Columbia	Canada (British Columbia)	introduced	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) Armoracia rusticana is listed in a table entitled "lien species recognized to be established in Japan or found in the Japanese wild (as of October 27, 2004)"
United States (west coast) United States (west coast states)	USA (Oregon)	introduced	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414
United States (west coast) United States (west coast states)	USA (California)	introduced	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414
United States (west coast) United States (west coast states)	USA (Washington)	introduced	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Canada Canada	Canada	introduced invasive	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414; "Canada B.C.Canada Man.Canada N.B.Canada N.S.Canada Ont.Canada P.E.I.Canada Que.Canada Sask."; cites as "noxious weed that is very difficult to eradicate," but not in any location in particular
Canada Canada	Canada	introduced invasive cultivated	Meewasin Valley Authority (2016) accessed 20180414
Europe Europe	Europe	native	Smekalova, T./Maslovky, O. (2011) accessed 20170927
Europe Europe	Europe		Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414
United States of America United States	United States	introduced invasive	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414; "USA Calif.USA Colo.USA Conn.USA IdahoUSA Ill.USA Ind.USA IowaUSA MaineUSA Mass.USA Mich.USA Minn.USA Mo.USA Mont.USA Nebr.USA N.H.USA N.J.USA N.Mex.USA N.Y.USA N.C.USA N.Dak.USA OhioUSA Oreg.USA Pa.USA R.I.USA S.Dak.USA Tenn.USA UtahUSA Vt.USA Va.USA Wash.USA W.Va.USA Wis.USA Wyo."; cites as "noxious weed that is very difficult to eradicate," but not in any location in particular
United States (continental except west coast) United States (other states)	United States (other states)	introduced	Al-Shehbaz, Ihsan A. (year unknown) accessed 20180414; "USA Calif.USA Colo.USA Conn.USA IdahoUSA Ill.USA Ind.USA IowaUSA MaineUSA Mass.USA Mich.USA Minn.USA Mo.USA Mont.USA Nebr.USA N.H.USA N.J.USA N.Mex.USA N.Y.USA N.C.USA N.Dak.USA OhioUSA Oreg.USA Pa.USA R.I.USA S.Dak.USA Tenn.USA UtahUSA Vt.USA Va.USA Wash.USA W.Va.USA Wis.USA Wyo."

Comments:  "Armoracia rusticana has been widely cultivated for about 2000 years for its fleshy roots that are grated to produce the pungent horseradish sauce." (Al-Shehbaz in JSTOR Plants)

Control:  "[Armoracia rusticana] is. . .a noxious weed that is very difficult to eradicate, [sic] even tiny root fragments are capable of regenerating new plants." (Al-Shehbaz in JSTOR Plants)

There is research that ". . .demonstrates the effectiveness of both halosulfuron and 2,4-D as components of an integrated management strategy for volunteer horseradish control and the potential for halosulfuron applications without soil persistence beyond 4 months impacting subsequent commercial horseradish production." (Johanning et al. 2016)