Sisymbrium orientale L. (syn.: S. columnae Jacq.) (E-Eur., Medit., Macaronesia) – A rather rare but much increasing, locally naturalised alien. Already recorded around Verviers in 1823. Subsequently seen in numerous widely scattered localities, mainly associated with grain (formerly also with wool). Most early records were apparently ephemeral although it was sometimes reported as persisting, for instance in ruderalised seadunes near Koksijde around 1920. Sisymbrium orientale is also known from gravel pits around Tournai since at least 1951 and is still present today (Querel 1994, 1995), along with S. loeselii. The subsequent naturalisation of Sisymbrium orientale in Belgium probably started in the 1980’s, mainly in urban areas around Antwerpen, Brussel and Gent (Saintenoy-Simon 1997, Verloove 2002, 2006c). In the past years also increasingly seen in smaller towns (Roeselare, Zeebrugge,…) and obviously also becoming naturalised. Sisymbrium orientale usually grows in dry, sun-exposed habitats: foot of walls, pavement, waste land,… It is still frequently introduced with cereals, sometimes also with building materials (ore, sand, gravel,…).
Sisymbrium orientale has been much confused with related species in Belgian herbaria, especially with S. altissimum. Both are readily distinguished by the presence or absence of horned sepals and by leaf shape (see key). Both often grow together in urban areas and, in some cases, Sisymbrium orientale increasingly seems to replace S. altissimum.
Selected literature:
Queyrel A.-M. (1994) Nouvelles observations dans les sites carriers du Tournaisis. Adoxa 3: 10.
Queyrel A.-M. (1995) Matériaux pouvant servir de complément à l’Atlas et observations annexes en Tournaisis. Adoxa 8: 27.
Saintenoy-Simon J. (1997) Le Quartier Nord, à Bruxelles, une pépinière d’espèces rares. Adoxa 17: 22-24.
Saintenoy-Simon J., Godefroid S. & Verhelpen B. (1995) Groupe Flore Bruxelloise. Notes floristiques relatives à la Région de Bruxelles-Capitale (1991-1993). Adoxa 6-7: 27-37.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.
Verloove F. (2006c) Sisymbrium orientale. 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: 836-837.