Fact Sheets


Paspalum dilatatum Poir.

Family :

Famille :


Synonym(s) :

Synonyme(s) :

Digitaria dilatata (Poir.) Coste (CABI 2021)

Common Name(s) :

Nom(s) commun(s) :

Dallis grass
(English) (GC 2016)

Herbe de Dallis (French) (GC 2016)

Caterpillar grass (English) (CABI 2021)

Grama de agua (Spanish) (CABI 2021)

Capim-comprido (Portuguese) (CABI 2021)

Brasilianische futterhirse (German) (CABI 2021)

  • Dallis grass (Paspalum dilatatum) spikelets

  • Dallis grass (Paspalum dilatatum) spikelets

  • Dallis grass (Paspalum dilatatum) spikelet

  • Dallis grass (Paspalum dilatatum) spikelet, inner bracts are hard and shell-like with a faint grid pattern

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Regulation :

Remarques Réglementation:

  • CFIA Weed Seeds Order - Class 1: Prohibited Noxious Weed Seeds
  • List of Pests Regulated by Canada

Regulation Notes:

Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order (2016) under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.

Distribution :

Répartition :

Native to South America and introduced to southern Europe, tropical and southern Africa, Asia, Australia, New Zealand and North America (CABI 2021; USDA-ARS 2021). Absent from Canada (Brouillet et al. 2010+).

Habitat and Crop Association :

Habitat et Cultures Associées :

Dry prairie, marshy meadows, shrublands, riparian habitats, freshwater wetlands, lawns, golf courses, sports fields, waste places (Holm et al. 1977; CABI 2021). Known as a weed of pastures, Musa species (bananas), Oryza sativa (rice) and vegetables in different parts of the world (Holm et al. 1977).

Economic Use, cultivation area, and Weed Association :

Utilisation économique, zone de culture et association de mauvaises herbes :

Duration of Life Cycle :

Durée du cycle vital:


Dispersal Unit Type :

Type d’unité de dispersion :


General Information


Paspalum dilatatum was introduced from Argentina or Uruguay into the southern United States in the 1800s as a forage grass and a turf grass (Barkworth et al. 2003). Seed contaminated with P. dilatatum is a potential introduction pathway into new areas (CABI 2021).

P. dilatatum is characterized by poor seed set caused by susceptibility to ergot infection and reproductive factors such as: self-fertilization, multiple developing embryos in an ovule and variable pollen viability (Reusch 1961).




  • Spikelet


    • Spikelet length*: 2.3 – 3.4 mm; width: 1.6 – 2.1 mm
    *Note: minimum and maximum of 20 spikelets in a normal range of this species using image measurement (ISMA 2020)


    • Spikelet is wide egg-shaped with a truncate wide end, compressed plano-convex shaped in edge view with tip tapered

    Surface Texture

    • Surface texture of upper glume and sterile lemma of spikelet are papery, gland-dotted with long hairs concentrated along edges
    • Upper glume and sterile lemma 5–7-veined (Allen 2012), the central nerve is prominent


    • Spikelet is dull or shiny straw yellow or light brown, rarely purple coloured

    Other Features

    • Lower glume of the spikelet is absent (Allen 2012)
  • Floret


    • With papery glume and sterile lemma, the floret size similar to spikelet size


    • Floret is egg-shaped, with a truncate wide end, compressed plano-convex in 3 dimensions

    Surface Texture

    • Fertile floret is hard and shell-like with a densely papillate surface texture


    • Floret is shiny light yellow
  • Caryopsis


    • Caryopsis length: 2.0 – 2.3 mm (Barkworth et al. 2003)


    • Caryopsis is egg-shaped

    Surface Texture

    • Caryopsis surface is smooth


    • Caryopsis is white, yellow or light brown
  • Embryo


    • Embryo is 2 – 2.3 mm long (Allen 2012)


    • Embryo is oval-shaped, in a lateral position at one end of the caryopsis


    • Endosperm is hard and translucent whitish coloured

    Other Features

    • White to brown colored (Allen 2012)

Identification Tips


The combination of a compressed shape in edge view along with a hairy, gland-dotted surface are distinctive for P. dilatatum spikelets. Other species generally have hairless spikelets with humped profiles. Other factors such as size, floret surface or number of nerves may be examined to distinguish P. dilatatum spikelets from similar species.

Additional Botany Information



  • Spikelets are arranged in pairs along a long flowering stem
  • Spikelets appressed to rachis (Allen 2012)

Vegetative Features

  • The flowers are believed to be pollinated by insects as well as by wind (Adams et al. 1981)

Similar Species


Similar species are based on a study of seed morphology of various species, and those with similar dispersal units are identified. The study is limited by physical specimen and literature availability at the time of examination, and possibly impacted by the subjectivity of the authors based on their knowledge and experience. Providing similar species information for seed identification is to make users aware of similarities that could possibly result in misidentification.

Paspalum laeve Michx

P. laeve spikelets are shorter and wider (length*: 2.1 – 2.9 mm; width: 1.7 – 2.6 mm) than P. dilatatum, although there is some overlap. P. laeve spikelets are humped, rather than compressed in edge view, the spikelet lacks surface hairs, and the floret has a smooth surface compared to P. dilatatum.

*Note: minimum and maximum of 10 spikelets in a normal range of this species using image measurement (ISMA 2020)

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Adams, D. E., W. E. Perkins and J. R. Estes. 1981. Pollination systems in Paspalum dilatatum Poir. (Poaceae): An example of insect pollination in a temperate grass. American Journal of Botany 3: 389-394.

Allen, C. 2012, Paspalum dilatatum, in Jepson Flora Project (eds.) Jepson eFlora, https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=36384, Accessed May 07, 2021.

Barkworth, M. E., K. M. Capels, S. Long, and M. B. Piep, (eds.) 2003. Flora of North America Volume 25. Magnoliophyta: Commelinidae (in part): Poaceae, part 2. Oxford University Press, New York, New York.

Brouillet, L., F. Coursol, M. Favreau and M. Anions 2010+. VASCAN, the database vascular plants of Canada, http://data.canadensys.net/vascan/ Accessed April 7, 2021.

Centre for Agriculture and Bioscience International (CABI). 2021. Invasive Species Compendium, CAB International, Wallingford, UK. https://www.cabidigitallibrary.org/journal/cabicompendium Accessed April 7, 2021.

Flora of North America (FNA) Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 22+ vols. New York and Oxford.  Accessed December 29, 2022.

Global Biodiversity Information Facility (GBIF) Secretariat. 2022. https://doi.org/10.15468/39omei Accessed via https://www.gbif.org/species/2705565 Accessed December 29, 2022.

Government of Canada (GC). 2016. Canadian Weed Seeds Order. https://laws-lois.justice.gc.ca/eng/regulations/SOR-2016-93/page-2.html (English) https://laws-lois.justice.gc.ca/fra/reglements/DORS-2016-93/page-2.html (French)

Holm, L. G., Plucknett, D. L., Pancho, J. V. and Herberger J. P. 1977. The World’s Worst Weeds, Distribution and Biology. Krieger Publishing Company, Florida. 609 pp.

International Seed Morphology Association (ISMA). 2020. Method for Seed Size Measurement. Version 1.0. ISMA Publication Guide.

Reusch, J. D. H. 1961. The relationship between reproductive factors and seed set in Paspalum dilatatum. South African Journal of Agricultural Science 4: 513-530.

U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). 2021. Germplasm Resources Information Network (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysimple.aspx Accessed April 7, 2021.



Jennifer Neudorf, Angela Salzl, Ruojing Wang, Karen Castro, Katrina Entwistle
Canadian Food Inspection Agency