1. Armoracia rusticana P. Gaertn., B. Mey. et Scherb. (origin obscure, probably Eurasia) – A rather frequent, locally naturalized relic from cultivation or garden throw-out. Cultivated as a condiment (horseradish) in Belgium since many centuries. Reports as an escape date back to at least 1853 (Mariakerke, coastal dunes). Subsequently recorded in very numerous and widely scattered locations. Already said to be abundantly naturalized in rather remote, damp meadows between Aarschot and Betekom around 1859. Long term presences have furthermore been demonstrated (from herbarium sources) from Bredene (1870-1953), Visé (1870-1909), etc. At present Armoracia rusticana is obviously well-established in Belgium although it is much less cultivated nowadays (see for instance Saintenoy-Simon 1995, Verloove 2002, Verloove 2006).
Armoracia rusticana is most often naturalized in road verges, canal and railway banks and waste land (formerly also in meadows). Soils are mostly rather damp and nitrophilous.
Once established it is very persistent and hard to eradicate. However, reproduction seems to be solely vegetative which prevents a wider expansion. Cultivated plants of Armoracia rusticana have an irregular meiosis (fruits are never produced) and are perhaps of hybrid origin (Mabberley 2008).
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References:
Chauhan A., Geiger K., Hanif M., Manek J., Patel G., Patel Y. & Rumney P. (1974) Exhibiton Meeting, 1973. Heterophylly in Armoracia rusticana. Watsonia 10: 225.
Fosberg F.R. (1965) Nomenclature of the Horseradish (Cruciferae). Baileya 13: 1-4.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Rhodes A.M., Courter J.W. & Shurtleff M.C. (1965) Identification of horseradish types. Trans. Illinois State Acad. Sci. 58: 115-122.
Saintenoy-Simon J. (1995) Excursion du 10 octobre 1994 à Obigies (province de Hainaut). Adoxa 8: 22-24.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006) Armoracia rusticana. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 158.