Erucastrum C. Presl
(incl. Hirschfeldia Moench)
The delimitation of Erucastrum is under study. As currently understood (see Warwick & Al-Shehbaz 2003, Mabberley 2008) it is a genus of about 20 species, native to the Mediterranean region, Macaronesia and parts of Central and Southern Europe. The exact placement of species from East- and South-Africa (see Schulz 1919) is debated but at least some pertain to Erucastrum (Warwick & Al-Shehbaz l.c.). One species, Erucastrum supinum (L.) Al-Shehbaz & Warwick (traditionally placed in Sisymbrium as S. supinum L.), is an extinct native species. Morphological and phylogenetic studies (Warwick & Al-Shehbaz l.c.) have shown that it is much more closely related to Erucastrum and Diplotaxis than it is to Sisymbrium. Although morphologically very distinct Hirschfeldia is genetically closely related to Erucastrum and molecular studies (Warwick & Black 1993) support its inclusion in a broadly circumscribed genus Erucastrum. Likewise, Brassica and Diplotaxis are probably also better merged with Erucastrum. The separation of these genera is highly artificial (Warwick & Black 1993). Yet, pending further research Erucastrum and Hirschfeldia are still accepted as separate genera in the recent account for Flora of North America (Warwick 2010a, b).
According to Lawalrée (1956) Belgian records of Erucastrum nasturtiifolium always turned out to be erroneous. However, it was reliably recorded in Belgium in 1936 (Verloove 2006) and is naturalised in abundance on a coalmine heap near Lens in northwestern France. It might occur in similar habitats in Belgium as well. It has an ebracteate inflorescence, clasping leaves and patent sepals.
1. Inflorescence ebracteate. Siliquae adpressed to stem, 8-17 mm long. Pedicel thick, nearly as wide as the siliqua === Erucastrum incanum
1. Inflorescence bracteate. Siliquae erecto-patent, not adpressed to stem, 10-45 mm long. Pedicel slender, much narrower than the siliqua === 2
2. Petals whitish. Stem procumbent. Seeds in two rows in each loculus (native) === E. supinum
2. Petals pure yellow. Stem erect. Seeds in one row in each loculus === E. gallicum
Additional alien: Erucastrum nasturtiifolium (Poiret) O.E. Schulz (syn.: E. obtusangulum (Schleich.) Clairv.) (SW-Eur., vector unknown).
Al Shehbaz I.A. (2005) (1678) Proposal to conserve the name Erucastrum against Kibera and Hirschfeldia (Brassicaceae). Taxon 54: 204-205.
Gómez-Campo C. & Martínez-Laborde J.B. (1998) Reajustes taxonómicos y nomenclaturales en la tribu Brassiceae (Cruciferae). Anales del Jardín Botánico de Madrid 56(2): 379-381.
Lawalrée A. (1956) Cruciferae. In: Robyns W. (ed.), Flore Générale de Belgique, vol. 2, fasc. 2. Jardin Botanique de l’Etat, Bruxelles: 160-285.
Loos G.H. (2004) Umgrenzung und Gliederung der Gattungen der Brassicaceen-Tribus Brassiceae in Mitteleuropa. Flor. Rundbr. Beih. 7: 113-135.
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Schulz O.E. (1919) Erucastrum. In: Engler A. (ed.), Das Pflanzenreich 70(IV.105). Engelmann, Leipzig: 88-106.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p.
Warwick S.I. & Black L.D. (1993) Molecular relationships in subtribe Brassicinae (Cruciferae, tribe Brassiceae). Can. J. Bot. 71: 906-918.
Warwick S.I. & Al-Shehbaz I.A. (2003) Nomenclatural notes on Sisymbrium (Brassicaceae). Novon 13: 265-267.
Warwick S.I. (2010a) Erucastrum. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 435-436.
Warwick S.I. (2010B) Hirschfeldia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 436-437.