1. Diplotaxis erucoides (L.) DC. (SW-Eur.) – A rare but apparently increasing alien, sometimes temporarily persisting or more or less naturalized locally. First recorded in 1920 in ruderalized sea dunes near a farm between Koksijde and Sint-Idesbald (subsequently confirmed there in 1922 and 1928). From 1994 onwards increasingly observed, initially as a grain alien (for instance in the port of Roeselare in 1994 and 2001; see Verloove & Vandenberghe 1995). Furthermore also recorded sometimes as a garden weed, for instance in Angleur in 2002 and in 2006 near Vorst (in abundance). Since 2008 frequently observed as a weed in imported containers with olive trees from southern Europe (Hoste & al. 2009). Locally also escaping in and near plant nurseries and showing some tendencies towards naturalization.
Diplotaxis erucoides is an unshowy crucifer and might easily pass unrecorded. In general appearance it most closely resembles white-flowered forms of Raphanus raphanistrum but Diplotaxis has siliquae that split longitudinally and seeds are disposed in two rows.
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References
Bernhardt K.-G., Laubhann D. & Kropf M. (2008) Chorispora tenella, Diplotaxis erucoides und Capsella rubella (Brassicaceae) in Wien und Niederösterreich. Neilreichia 5: 211-216.
Hoste I., Verloove F., Nagels C., Andriessen L. & Lambinon J. (2009) De adventievenflora van in België ingevoerde mediterrane containerplanten. Dumortiera 97: 1-16.
Martínez Laborde J.B. (1991) Notes on the taxonomy of Diplotaxis DC. (Brassiceae). Bot. J. Linn. Soc. 106(1): 67-71.
Martínez Laborde J.B. & Méndez E. (2001) Una nueva crucífera adventicia en Argentina. Bol. Soc. Argent. Bot. 36: 143-146.
Radkowitsch A. (2010) Diplotaxis erucoides - aktuelles Vorkommen einer seltenen Adventivart in Süddeutschland. Floristische Rundbriefe 44: 113-119.
Sans F.X. & Masalles R.M. (1994) Life history variation in the annual arable weed Diplotaxis erucoides (Cruciferae). Canad. J. Bot. 72: 10-19.
Verloove F. & Vandenberghe C. (1995) Nieuwe en interessante voederadventieven voor de Belgische en Noordfranse flora, hoofdzakelijk in 1994. Dumortiera 61-62: 23-45.