Matricaria discoidea DC. (syn.: Chamomilla suaveolens (Pursh) Rydberg, C. discoidea (DC.) J. Gay ex A. Braun) (NE-As., N-Am.) – A commonly and widely naturalized alien. First reliably recorded in 1893 in Wilsele, apparently as a grain alien, (confirmed in 1894). Possibly already observed as soon as 1874 (Hoste 2006). Soon afterwards also observed in Lambermont (1896), Bévercé (Dison) (1899), etc. and already known from scattered locations in the beginning of the 20th century. By 1925 considered to be an agricultural weed in the surroundings of Antwerpen and around 1935 already common throughout (Hoste 2006). At present very common and omnipresent in most of Belgium. Matricaria discoidea is found in a wide range of man-made and more natural habitats: waste land, arable land, pavement, dumps, road verges, farmyards, gateways, pond margins, etc.
A very similar species, Matricaria occidentalis E. Greene (perhaps a mere subspecies of M. discoidea, subsp. occidentalis (E. Greene) P.D. Sell), is known from Ireland (Sell & Murrell 2006). It usually has larger heads (8-12 mm across) and a pappus that is distinctly 2-lobbed. It may have been overlooked in Belgium. However, in its area of origin this species is rather local and decreasing and, moreover, confined to natural habitats (Brouillet 2006). Its presence as an alien in Europe is rather surprising.
Selected literature:
Amat A.G. (1985) Matricaria matricarioides (Less.) Porter (Compositae, Anthemideae) adventicia en la Provincia de Buenos Aires. Univ. Nacion. La Plata, Fac. Cienc. Nat. Mus., Notas Mus. La Plata 21(96): 4p.
Applequist W.L. (2002) A reassessment of the nomenclature of Matricaria L. and Tripleurospermum Sch. Bip. (Asteraceae). Taxon 51(4): 757-761.
Brouillet L. (2006) Matricaria. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 19. Oxford University Press, New York-Oxford: 540-542.
Djavadi S.B., Naqinezhad A. & Ramezankhah S. (2007) Matricaria discoidea, a new species of the Asteraceae - Anthemideae for the flora of Iran. Rostaniha 8(2): 106-107.
Heath P.V. (1994) Commentary on the proposal to conserve Matricaria Linné. Calyx 4: 48-50.
Hoste I. (2006) Matricaria discoidea. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. Instituut voor Natuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 576-577.
Jeffrey C. (1979) Note on the lectotypification of the names Cacalia L., Matricaria L. and Gnaphalium L. Taxon 28: 349-351.
Kay Q. & Hutchinson G. (1993) The truth about Pineapple Weed? BSBI News 63: 51.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H.) (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Mitsuoka S. & Ehrendorfer F. (1972) Cytogenetics and evolution of Matricaria and related genera. Österr. Bot. Z. 120: 155-200.
Oberprieler C. (2001) Phylogenetic relationships in Anthemis L. (Compositae, Anthemideae) based on nrDNA ITS sequence variation. Taxon 50: 745-762.
Rauschert S. (1974) Nomenklatorische Probleme in der Gattung Matricaria L. Folia Geobot. Phytotax. 9: 249-260.
Sell P. & Murrell G. (2006) Flora of Great Britain and Ireland. Vol. 4 Campanulaceae – Asteraceae. Cambridge University Press, Cambridge: XXVIII + 624 p.