Lepidium bonariense
Lepidium bonariense L. (S-Am.) – A rare and ephemeral alien but possibly under-recorded (poorly known). Observed as a wool alien in the Vesdre valley between 1906 and 1955. Occasionally seen elsewhere, for instance on a dump in Merksem in 1953 (possibly from birdseed). More recently recorded at several locations as a roadside alien (doubtlessly from grain) in the port of Gent in 1985 (Robbrecht & Jongepier 1986) and confirmed in this area in 2003. However, it is uncertain whether or not this represents an independent record (a naturalisation seems rather unlikely). Furthermore seen along motorway A17 near Aalbeke in 2002.
Lepidium bonariense is a very inconspicuous species and easily passes unrecorded. Confusion is most likely with Lepidium densiflorum and L. virginicum (all with more or less orbicular silicula and narrowly winged seeds). It is best distinguished by the deeply pinnately lobed upper leaves and furthermore shares the elongated stem hairs with Lepidium virginicum. Unlike the latter, Lepidium bonariense has very small petals (shorter than the sepals). It finally differs from Lepidium densiflorum by the longer, not papillose hairs.
Selected literature:
Anzalone B. (1970) Una nuova avventizia per l'Italia ed il sudeuropa: Lepidium bonariense L. Inform. Bot. Ital. 2: 42-44.
Robbrecht E. & Jongepier J.-W. (1986) Floristische waarnemingen in de kanaalzone Gent-Terneuzen (België, Oost-Vlaanderen & Nederland, Zeeuws-Vlaanderen), vooral van 1981 tot 1985. Dumortiera 36: 6-21.