Erucastrum incanum (L.) Koch (syn.: Hirschfeldia incana (L.) Lagrèze-Fossat, H. adpressa Moench, Sinapis incana L.) (Medit., Macaronesia) – A naturalised and fast-spreading alien. Apparently first recorded in 1873 in Lissewege (initially as Brassica nigra and not recognised before ca. 1890). Soon spreading locally and subsequently also observed in Blankenberge, Heist and Knokke (ruderalised sea dunes, road verges). Established inland populations were discovered from 1922 onwards on a railway embankment between Zaventem and Diegem. Here also soon spreading and locally naturalising (see also Saintenoy-Simon & al. 1995). Further early records were usually ephemeral. Erucastrum incanum, for instance, was formerly also observed as a wool alien in the Vesdre valley. In the past decades much increasing and possibly still confused with Brassica nigra. By now best represented in coastal areas (mainly Oostkust and valley of river IJzer) and furthermore in the vicinity of the larger cities (Antwerpen, Brussel, etc.) (Vanhecke 2006). However, by far most records are from Flanders; apparently very rare in Wallonia (but possibly overlooked).
Erucastrum incanum was long confused with Brassica nigra in Belgium. Both are tall, divaricately branched annuals or biennials with short adpressed siliquae. However, Erucastrum incanum has sepals with scattered hairs (best seen in bud) and siliquae with a distinct beak (4-7 mm long) with 0-2 seeds. In Brassica nigra sepals are glabrous and siliquae have a shorter (1-4 mm) seedless beak.
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Selected literature
Jehlík V. & Štěpánek J. (1983) Hirschfeldia incana v Československu. Preslia 55: 315-323.
Rich T.C.G. (1988) Hirschfeldia incana (L.) Lagreze-Fossat present in Ireland. Irish Naturalists' J. 22: 531-532.
Saintenoy-Simon J. & Bruynseels G. (1982) Hirschfeldia incana (L.) Lagrèze-Fossat, Corispermum leptopterum (Aschers.) Iljin et Senecio inaequidens DC. dans la gare Josaphat (Schaerbeek, Bruxelles). Dumortiera 23: 26-28.
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.
Vanhecke L. (2006) Hirschfeldia incana. 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: 471-472.