Xanthium spinosum L. s.l. (syn.: Acanthoxanthium spinosum Fourr.; incl. X. ambrosioides Hook. et Arnott) (Am.) – A rare and decreasing, ephemeral alien. Perhaps first collected in 1848 in Elsene (Brussels). Formerly, especially in the 19th century, a rather frequent alien. Also a typical wool alien in the Vesdre valley near Verviers, at least between 1867 and 1970. Dramatically decreasing lately and since 1950 only recorded on few occasions, for instance in Leuze (1954), Ekeren (1959), Elsene (1959), Mechelen (1967), Braine-le-Comte (1971), Turnhout (1976), Welle (1980), Gent (1983 and 1997), Laakdal (1990), Merksem (1994), Deinze (2008), Ruiselede (2011) and Nassogne (2012). Most recently seen on the verge of a maize field in Lokeren in 2015, obviously from discarded birdseed waste. Nearly all recent records are obviously associated with grain importation: unloading quays, near grain mills, dumps, etc.
Xanthium ambrosioides (syn.: Acanthoxanthium ambrosioides (Hook. et Arnott) D. Löve), often treated as a separate species, was recorded as a wool alien in the Vesdre valley in 1906 and 1907 (Lambinon 1995). It has more deeply lobed leaves with a longer petiole, shorter spines and smaller burs (4-9 mm long).
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Selected literature:
Baduraj D.S., Britto S.J. & Michael P. (1994) Xanthium spinosum L.: a new record for Tamilnadu. J. Econ. Taxon. Bot. 18(1): 235-238.
Dar G.H., Naqshi A.R. & Ara S. (1990) Xanthium spinosum L. - a new record for the Indian Subcontinent. J. Bombay Nat. Hist. Soc. 87(2): 329-331.
Lambinon J. (1995) Notes taxonomiques, nomenclaturales et chorologiques relatives à la quatrième édition de la « Nouvelle Flore » de la Belgique et des régions voisines. 3. Données nouvelles sur des plantes adventices ou subspontanées en Belgique. Dumortiera 60: 1-36.
Klotz J. (2007) Die Xanthium-Arten bei Regensburg, mit einem Wiederfund von Xanthium spinosum für Ostbayern. Hoppea 68: 191-196.
Löve D. (1975) The genus Acanthoxanthium (DC.) Fourr. revived. Lagascalia 5: 55-71. [available online at: http://bibdigital.rjb.csic.es/Imagenes/P0422_05/P0422_05_063.pdf]
Metwally A.M. & Khafagy S.M. (1975) Macro and micromorphology of Xanthium spinosum L. Egypt. J. Pharm. Sci. 16(2): 129-141.
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.
Verloove F. & Vandenberghe C. (1995) Nieuwe en interessante voederadventieven voor de Belgische en Noordfranse flora, hoofdzakelijk in 1994. Dumortiera 61-62: 23-45.
Widder F.J. (1964) Die Veränderlichkeit von Xanthium spinosum. Phyton (Horn) 11: 31-33.