Brassica tournefortii Gouan (Medit.) – A very rare and always ephemeral alien. It was first collected in 1922 in Vorst (Brussel) as a weed in an oat-field. Subsequently it was seen near a gravel pit in Hargimont (Marche-en-Famenne) in 1960. These records remained unidentified for quite a long time. The species was first formally recognized from Belgium in 1992 and 1994 when it occurred as grain alien on an unloading quay in the port of Roeselare (Verloove & Vandenberghe 1996). Subsequently, it was also observed near a grain elevator in the port of Gent in 1997 and on an unloading quay at the Kattendijkdok in the port of Antwerpen in 2004. It was most recently seen as an urban weed in Gent in 2007, possibly as a birdseed alien, and by a roadside in the port of Gent (Rodenhuizedok, as a grain alien) in 2012 and 2013.
Brassica tournefortii is rather characteristic but apparently poorly known in Belgium. It has tiny, very pale yellow petals (turning white in the herbarium), lyrate-pinnatisect rosette leaves, siliqua with a long beak and, densely hirsute stems.
In recent years Brassica tournefortii is a fast spreading invasive species in desert-like areas in the southern United States (e.g. Trader & al. 2006, Bangle & al. 2008, Berry 2014).
Selected literature:
Bangle D.N., Walker L.R. & Powell E.A. (2008) Seed germination of the invasive plant Brassica tournefortii (Sahara mustard) in the Mojave Desert. Western North American Naturalist 68(3): article 8. [available online at: https://scholarsarchive.byu.edu/wnan/vol68/iss3/8]
Berry K., Gowan T., Miller D. & Brooks M. (2014). Models of Invasion and Establishment for African Mustard (Brassica tournefortii). Invasive Plant Science and Management 7(4): 599-616.
Chauhan B.S., Gill G. & Preston C. (2006) African mustard (Brassica tournefortii) germination in southern Australia. Weed Science 54: 891–897.
Trader M.R., Brooks M.L. & Draper J.V. (2006) Seed production by the non-native Brassica tournefortiii (Sahara mustard) along desert roadsides. Madroño 53: 313–320.
Verloove F. & Vandenberghe C. (1996) Nieuwe en interessante voederadventieven voor de Belgische flora, hoofdzakelijk in 1995. Dumortiera 66: 11-32. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/dum66p11....