Panicum capillare

1. Panicum capillare L. (N-Am.) – A rather regular alien, formerly primarily introduced with wool, currently almost exclusively as a grain alien. Usually found as an ephemeral alien in port areas (near unloading quays and grain storage, wasteland, by roadsides and railway tracks or on dumps). In recent times increasingly found as an agricultural weed as well, chiefly in maize fields in parts of Flanders (Hoste & Verloove 2001, Hoste 2006) and then sometimes more or less naturalized. Also sometimes associated with coal, for instance on a coal mine heap in Anderlues (2008) or on a former coal terminal at the Albertkanaal in Beringen (2009), twice in abundance.

Panicum capillare is a variable species and member of a taxonomically difficult species-complex (Fairbrothers 1953, Darbyshire & Cayouette 1995, Freckmann & Lelong 2003). The present treatment of the group slightly differs from that proposed by Freckmann & Lelong l.c. in that Panicum hillmanii is retained at specific level (and not as a subspecies of P. capillare; see there) and subspecies barbipulvinatum (Nash) Tsvelev [syn.: P. barbipulvinatum Nash, P. capillare var. barbipulvinatum (Nash) McGregor, P. capillare var. occidentale Rydb.] – readily distinguished from the typical subspecies in Europe but apparently much less so in the New World – is upheld as well. Subspecies barbipulvinatum and capillare are distinguished in the following couplet:

  • Spikelets acute-acuminate, at most 2,5 mm long === subsp. capillare
  • Spikelets long-acuminate, sometimes almost pencil-like, usually ca. 3 mm long === subsp. barbipulvinatum

Subsp. capillare is by far the least rare of both subspecies. Subsp. barbipulvinatum has rarely been collected in Belgium (Verloove 2001) and usually remains strictly casual. However, several seemingly established populations were seen on a railway yard in Brugge in 2013. In 2014 also seen in Geel and Lommel. Possibly overlooked. In the Netherlands this taxon is more frequent than subsp. capillare (Dirkse & Holverda 2016).

Some very similar species are possibly overlooked and should be looked for. The recently described Panicum riparium H. Scholz – initially confined to sandy riverbanks of rivers Elbe and Oder in Germany – increasingly occurs elsewhere in Europe as well (see for instance Scholz 2002, Hohla 2006, Garve 2008). It has a laxer, few-flowered inflorescence with shortly pedicellate, narrower spikelets that are long-acuminate at apex. It is only poorly distinguished from Panicum capillare, especially from its subsp. barbipulvinatum. Indeed, Amarell (2013 a,b) demonstrated that Panicum riparium and P. barbipulvinatum are in fact conspecific and proposed species rank for this taxon. A more distinct species occurs as a weed of maize fields (more rarely also on river banks) in parts of Central- and southern Europe (e.g. Austria, Italy, Spain): Panicum philadelphicum Bernh. ex Trin. (syn.: P. gattingeri Nash) (see for instance Melzer 1985, Verloove & Sánchez Gullón 2008, Verloove & al. 2010). Its panicles are always less than ½ the total height of the plant and its spikelets are smaller (1,9-2,4 mm long) and acute at apex (not acuminate). It should be looked for in Belgium as well.

Herbarium specimen 1

Herbarium specimen 2

Herbarium specimen 3

Panicum capillare, Brugge, industrial area, September 2008, E. Molenaar

Panicum capillare, Mol, pavement weed in urban area, October 2010, R. Barendse

  Panicum_capillare subsp. capillare, spikelet             

Panicum_capillare subsp. barbipulvinatum, spikelet

Panicum capillare, leaf sheath


Selected literature:

Amarell U. (2013a) Panicum riparium H. Scholz – eine neoindigene Art Europas? Kochia 7: 1-24.

Amarell U. (2013b) Panicum barbipulvinatum (= Panicum riparium) in Baden-Württemberg. Berichte der Botanischen Arbeitsgemeinschaft Südwestdeutschlands 7: 3-10.

Amarell U. (2014) Panicum barbipulvinatum Nash (= Panicum riparium H. Scholz) - Eine übersehene Art in der Schweiz. Bauhinia 25: 69-68. [available online at:]

Darbyshire S.J. & Cayouette J. (1995) Identification of the species in the Panicum capillare complex (Poaceae) from eastern Canada and adjacent New York State. Can .J. Bot. 73: 333-348.

Dirkse G. & Holverda W. (2016) Panicum capillare  L. (Draadgierst) en Panicum barbipulvinatum Nash in Nederland: eerherstel voor een miskende soort. Gorteria 38: 34-42. [available online at:

Fairbrothers D.E. (1953) Relationships in the Capillaria group of Panicum in Arizona and New Mexico. Amer. J. Bot. 40: 708-714.

Freckmann R.W. & Lelong M.G. (2003) Panicum. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 25: 450-488. Oxford University Press, New York-Oxford.

Garve E. (2008) Nachweise der Süssgräser Vulpia membranacea und Panicum riparium (Poaceae) im westlichen Niedersachsen. Braunschw. Geobot. Arb. 9: 167-175.

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.

Hoste I. (2006) Panicum capillare. 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.

Király G. & Alegro A. (2015) Re-evaluation of the Panicum capillare complex (Poaceae) in Croatia. Acta Bot. Croatica 74(1): 1-8. [available online at:

Kump A. (1974) Panicum capillare L. als Ackerunkraut in Oberösterreich. Mitt. Bot. Arbeit. Oberösterr. Landesmus. Linz 6(1): 59-61.

Lambinon J. (2006) Panicum capillare subsp. barbipulvinatum dans un champ de mais de l'Oesling (Grand-Duche de Luxembourg). Dumortiera 89: 22-23.

McGregor R.L. (1984) Panicum capillare L. var. barbipulvinatum (Nash) comb. nov. Phytologia 55(4): 256.

Melzer H. (1985) Beiträge zur Flora von Friaul-Julisch Venetien und angrenzender Gebiete (Italien, Jugoslawien). Gortania 6: 175-190.

Schaberg F. (1983) Panicum capillare L. – Herkunft und Verbreitung einer bemerkenswerten Adventivpflanze unter besonderer Berücksichtigung der Fundorte in Sachsen. Gleditschia 10: 121-130.

Scholz H. (2002) Panicum riparium H. Scholz – eine neue indigene Art der Flora Mitteleuropas. Feddes Repert. 113(3-4): 273-280.

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. & Sánchez Gullón E. (2008) New records of interesting xenophytes in the Iberian Peninsula. Acta Botanica Malacitana 33: 147-167.

Verloove F., Banfi E., Galasso G., Zanotti E. & Ardenghi N. M. G. (2010) Notula 23 Panicum philadelphicum. In: Notulae alla flora esotica d’Italia: 2 (22-37). Nepi C., Peccenini S. & Peruzzi L. (eds.). Inform. Bot. Ital. 42 (1): 386.

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