1. Dysphania ambrosioides (L.) Mosyakin et Clemants (syn.: Chenopodium ambrosioides L.; excl. Dysphania anthelmintica (L.) Mosyakin et Clemants, Chenopodium anthelminticum L., C. ambrosioides var. anthelminticum (L.) A. Gray, C. suffruticosum Willd.) (Am.) – A rather frequent, locally naturalising alien. Already recorded as an agricultural weed in the first half of the 19th century in the surroundings of Gent. Formerly a frequent wool alien in the valley of river Vesdre near Verviers, at least between 1883 and 1967. In the past decades mostly associated with cereals (near grain mills, on grain dumps, under conveyors, by roadsides or railway tracks, etc.) or introduced without obvious vector of introduction.
Most of the time Dysphania ambrosioides appears as an ephemeral introduction. Genuinly naturalised populations are probably rare and confined to hot and sun-exposed places: rough grounds in port areas or in urban habitats, for instance in Gent. Current climatic circumstances in Belgium are probably not favorable for Dysphania ambrosioides. Further north, for instance in the Netherlands, it merely is an ephemeral alien.
In addition to typical D. ambrosioides, another more or less distinct form (a good species according to most recent authors; see Uotila 2001, Clemants & Mosyakin 2003, Iamonico 2011) has been recorded in Belgium, D. anthelmintica (see also there). They are distinguished in the following couplet:
- Inflorescence leafy to the top (glomerules subtended by leaf-like bracts) === D. ambrosioides
- Inflorescence leafless, at least in the upper half (small bracts sometimes present but these usually not subtending glomerules) === D. anthelmintica
Both taxa are insufficiently known in Belgium and perhaps not always easy to distinguish. However, the usual alien (and the only naturalised taxon) surely seems to be Dysphania ambrosioides s.str.
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Selected literature:
Buch C. & Keil P. (2012) Chenopodium ambrosioides in der Rheinaue bei Duisburg. Decheniana 165: 77-84.
Clemants S.E. & Mosyakin S.L. (2003) Dysphania. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 4. Oxford University Press, New York-Oxford: 267-275.
Iamonico D. (2011) Dysphania anthelmintica (Amaranthaceae), new to the non-native flora of Italy, and taxonomic considerations on the related species. Hacquetia 10(1): 41-48.
Schwarzová T. (1991) K rozsireniu synantropnych druhov Chenopodium ambrosioides L. a Chenopodium integrifolium Vorosch. Bull. Slov. Bot. Spoločn.13: 43-50.
Uotila P. (2001) Chenopodiaceae. In: Jonsell B. (ed.), Flora Nordica, vol. 2. The Bergius Foundation, Stockholm: 1-57.
Vercruysse W. (2006) Chenopodium ambrosioides. 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: 277.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.