Barbarea R. Brown
Barbarea is, depending on species delimitation, a genus of ca. 22-29 species native in the northern hemisphere. It is particularly well represented in Turkey and adjacent regions (Coode & Cullen 1965, Davis & al. 1988, Güner & al. 2000). Only one species is undoubtedly native in Belgium: Barbarea vulgaris R. Brown. The exact residence status of most other taxa is very controversial in Belgium. Barbarea intermedia Boreau is nowadays considered native but it might as well be a merely naturalized alien (compare Lawalrée 1957, Rich 1987, Ball 1993). The two remaining species currently found in Belgium (B. stricta and B. verna) are considered aliens in this account although at least the former may be native as well (but was long overlooked).
Barbarea vulgaris is a very variable species, often divided into several closely related (micro-) species. However, these probably do not deserve taxonomic recognition on a global scale. A rather distinct race with patent, arcuate siliquas is sometimes seen, for instance on a coal mining spoil heap near La Louvière (Houssu) in 2006; such plants may belong to subsp. arcuata (Opiz ex J. et C. Presl) Hayek [syn.: B. arcuata (Opiz ex J. et C. Presl) Reichenb.] (see also Loos 1996). It is a taxon originating in the eastern portion of the distribution range of Barbarea vulgaris. De Langhe (1992) further reported about the presence in Belgium of another taxon from the Barbarea vulgaris complex, subsp. rivularis (Matrin-Donos) Sudre (syn.: B. rivularis Matrin-Donos) (see also Lambinon & Verloove 2012 for their distinction). The distribution and residence status of these taxa in Belgium require further research.
The widespread North American Barbarea orthoceras Ledeb. is very similar to B. stricta and might have been overlooked. It has slightly larger petals and longer fruits (see Al-Shehbaz 2010).
1 Uppermost leaves and bracts nearly entire, toothed or shallowly lobed (rarely with 1 or 2 pairs of lateral lobes). Seeds ca. 1,6 mm long === 2
Uppermost leaves and bracts pinnatifid with 2 or more lateral lobes. Seeds ca. 2 mm long === 3
2 Flower buds pubescent near apex. Beak of siliqua 0,5-1,5 mm long at maturity. Terminal leaf segment of basal leaves often as long as the remainder of the leaf blade === Barbarea stricta
Flower buds glabrous. Beak of siliqua 2-4 mm long at maturity. Terminal leaf segment of basal leaves usually smaller than the remainder of the leaf blade (native) ==== B. vulgaris
3 Mature siliqua 30-70 mm long. Basal leaves with 13-21 segments. Petals ca. 6-8,5 mm long when fresh === B. verna
Mature siliqua (10-)15-30 mm long. Basal leaves with 5-11 segments. Petals ca. 4-5,5 mm long when fresh (native) === B. intermedia
Literature:
Al-Shehbaz I.A. (2010) Barbarea. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 7. Oxford University Press, New York-Oxford: 460-463. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=103484]
Al Shehbaz I.A. & Peng C.I. (2000) The genus Barbarea (Brassicaceae) in Taiwan. Bot. Bull. Acad. Sin. (Taipei) 41(3): 237-242. [available online at: http://ejournal.sinica.edu.tw/bbas/content/2000/3/bot13-10.html]
Ball P.W. (1993) Barbarea. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 1. (2nd ed.). Cambridge University Press, Cambridge: 342-343.
Coode M.J.E. & Cullen J. (1965) Barbarea R.Br. In: Davis P.H. (ed.), Flora of Turkey and the East Aegean Islands, Vol. 1, Edinburgh University Press, Edinburgh.
Davis P.H., Mill R.R. & Tan K. (eds.) (1988) Flora of Turkey and the East Aegean Islands (suppl.), Vol. 10, Edinburgh Univ. Press, Edinburgh.
De Langhe J.E. (1992) Barbarea rivularis de Matrin-Donos, crucifère négligée et méconnue de la flore européenne. Dumortiera 52: 25-27.
Güner A., Özhatay N., Ekim T. & Başer K.H.C. (eds.) (2000) Cruciferae: Flora of Turkey and the East Aegean Islands (suppl. 2) Vol. 11, Edinburgh University Press, Edinburgh.
Lambinon J. & Verloove F. (avec coll. Delvosalle L., Toussaint B., Geerinck D., Hoste I., Van Rossum F., Cornier B., Schumacker R., Vanderpoorten A. & Vannerom H.) (2012) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Sixième édition. Jardin botanique national de Belgique, Meise: CXXXIX + 1195 p.
Lawalrée A. (1957) Cruciferae. In: Robyns W. (ed.), Flore Générale de Belgique, vol. 2, fasc. 3. Jardin Botanique de l’Etat, Bruxelles: 287-404.
Loos G.H. (1996) Barbarea arcuata (Opiz ex J. & K. Presl) Rchb. – eine verkannte Winterkressen-Art. Flor. Rundbr. 30(1): 4-6.
Rauschert S. (1966) Ist Barbarea Ehrhart ein legitimer Gattungsname? Feddes Repert. 73: 222-225.
Rich T.C.G. (1987) The genus Barbarea R. Brown in Britain and Ireland. Watsonia 16: 389-396. [available online at: http://archive.bsbi.org.uk/Wats16p389.pdf]
Rich T. (1987) Identifying yellow crucifers: 1. Barbarea R. Br. Wild Flower Mag. 409: 42-44.