Panicum dichotomiflorum

3. Panicum dichotomiflorum Michaux (Am.) – A rather frequent and increasing alien, formerly mainly introduced with wool or seeds, in more recent times chiefly a grain alien. Probably first collected on wasteland in Merksem in 1881. Nowadays usually found in port areas, near grainstores, by roads or railway tracks, on dumps,… As a rule ephemeral in such habitats. However, since the 1980’s increasingly found as a spreading and naturalised agricultural weed, at first apparently in the Kempen (vicinity of Turnhout), subsequently also elsewhere in Flanders (Verloove 2001). Panicum dichotomiflorum is chiefly found so far on more or less sandy soils between Brugge and Gent (see Hoste & Verloove 2001) and in a more diffuse way in parts of the provinces of Antwerpen and Limburg. Likely to spread elsewhere in identical or other suitable habitats (on river banks for instance), especially in Flanders. At present probably absent in Wallonia or much less frequent than in Flanders.

Panicum dichotomiflorum is a rather variable species. Spikelet length and form can range from less than 3 mm to nearly 4 mm and from shortly acuminate to subobtuse. In habit prostrate, ascending as well as erect plants can be seen. Moreover, a recently discovered population (margin of a maize field near Torhout, 2008) is very aberrant in having lower florets that are mostly male instead of neuter (a character of Panicum schinzii)! This aberration was unmentioned so far in literature and considerably blurs the distinction between both species (especially since stamens might be exceptionally absent in Panicum schinzii; see under that species). However, Panicum schinzii always has lemma apices that are blunter and a more diffuse panicle with pedicels that are patent (in P. dichotomiflorum pedicels usually lay more or less parallel to the inflorescence branches).

Herbarium specimen

Panicum_dichotomiflorum, lemma & spikelet - Drawing S.Bellanger

Panicum dichotomiflorum, Meerhout, maize field, Augustus 2009, R. Barendse


Selected literature:

Braun W. (1986) Die Gabelästige Hirse, Panicum dichotomiflorum Michx., eine neue Art der bayerischen Flora. Ber. Bayer. Bot. Ges. 57: 75-80.

Csiky J., Kiraly G., Olah E., Pfeiffer N. & Virok V. (2004) Panicum dichotomiflorum Michaux., a new element in the Hungarian flora. Acta Bot. Hung. 46(1-2): 137-141.

Druet J. & Duvigneaud J. (1951) Note sur quelques phanérogames adventices. Lejeunia 15: 59-62.

Duhamel G. & Bosc G. (1980) Extension vers l’est de Panicum dichotomiflorum Michx. Monde Pl. 407: 1-2.

Fenaroli I. & Lorenzoni G.G. (1964a) Panicum dichotomiflorum, a new weed of maize crops in Italy, 1. Origin, description and occurence. Maydica 9: 35-40.

Fenaroli I. & Lorenzoni G.G. (1964b) Panicum dichotomiflorum, a new weed of maize crops in Italy, 2. Sociology and ecology. Maydica 9: 67-76.

Hoste I. (2006) Panicum dichotomiflorum. 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: 643-644.

Hoste I. & Verloove F. (2001) De opgang van C4-grassen (Poaceae-Paniceae) in de snel evoluerende onkruidvegetaties in maïsakkers tussen Brugge en Gent (Vlaanderen, België). Dumortiera 78: 2-11.

Hügin G. (2010) Panicum dichotomiflorum, P. hillmanii, (P. laevifolium), P. miliaceum subsp. agricola, P. miliaceum subsp. ruderale und Setaria faberi in Südwestdeutschland und angrenzenden Gebieten. Ber. Bot. Arbeitsgemeinschaft Südwestdeutschl. 6: 31-68.

Ilijanić L. & Marković L. (1986) Panicum dichotomiflorum Michaux in the surroundings of Zagreb. Acta Bot. Croat. 45: 137-139.

Lambinon J. (1991) Adventices grainières et autres plantes intéressantes observées en 1990 au port d’Anvers (Belgique). Dumortiera 49: 1-6.

Le Clerch J. (1973) Introduction d’une nouvelle Graminée en France: Panicum dichotomiflorum Michx. Bull. Soc. Bot. Fr. 120: 223-226.

Lippert W. (1984) Beiträge zu kritischen oder wenig beachteten Arten und Artengruppen der bayerischen Flora. Ber. Bayer. Bot. Ges. 55: 63-65.

Verloove F. (2001) A revision of the genus Panicum (Poaceae, Paniceae) in Belgium. Syst. Geogr. Pl. 71: 53-72.

Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.

Verloove F. & Vandenberghe C. (1993) Nieuwe en interessante graanadventieven voor de Noordvlaamse en Noordfranse flora, hoofdzakelijk in 1992. Dumortiera 53-54: 35-57.

Weber H.E. (1990) Panicum dichotomiflorum Michaux, ein neues Unkraut der Maisäcker in Nordwestdeutschland. Flor. Rundbr. 24: 13-18.

Zuloaga  F.O. (2022) Revisión de las especies de Panicum sect. Dichotomiflora (Poaceae: Panicoideae: Paniceae). Darwiniana, nueva serie 10(2): 325-364. [available online at:]

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith