Fact Sheets


Apera spica-venti (L.) P. Beauv.

Family :

Famille :


Synonym(s) :

Synonyme(s) :

Agrostis spica-venti L.

Common Name(s) :

Nom(s) commun(s) :

Common windgrass

(English) (Wiersema and León, 1999; Barkworth et al., 2007; USDA-ARS, 2021)
Loose silky-bent (English) (Wiersema and León, 1999; Barkworth et al., 2007; USDA-ARS, 2021; USDA-NRCS, 2021)
Silky-bent grass (English) (Warwick et al., 1985; Wiersema and León, 1999; Darbyshire, 2003; USDA-ARS-, 2021)
Windgrass (English) (Wiersema and León, 1999; AOSA, 2021; USDA-ARS, 2021)
Agrostide jouet-du-vent: (French) (Warwick et al., 1985; Wiersema and León, 1999 ; Darbyshire, 2003)

  • Silky bent grass (Apera spica-venti) florets

  • Apera spica-venti (common windgrass) floret in lemma view. Scale in mm.

  • Apera spica-venti (common windgrass) floret in lateral view. Scale in mm.

  • Apera spica-venti (common windgrass) floret in palea view. Scale in mm.

  • Silky bent grass (Apera spica-venti) florets

  • Silky bent grass (Apera spica-venti) floret

  • Silky bent grass (Apera spica-venti) floret

  • Silky bent grass (Apera spica-venti) floret

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Regulation :

Remarques Réglementation:

  • Quarantine lists of countries e.g. India *may be updated without notice
  • Quarantine lists of countries e.g. Mexico *may be updated without notice

Regulation Notes:

On Brazil, India, Mexico, and Republic of Korea lists of harmful organisms (USDA-PCIT-PExD 2021) (*may be updated without notice).

Distribution :

Répartition :

This species is native to much of Europe and temperate Asia and introduced in northern Africa, eastern Russia, Japan, Australia, North America and elsewhere (Walsh 2020; Ikeda et al. 2021; USDA-ARS 2021). In the United States, it occurs sporadically in 18 states, primarily in the northeast, the west, and Texas (USDA-APHIS 2016; USDA-NRCS 2021). In Canada, this species occurs in Ontario , where it has a restricted distribution (Warwick et al. 1985; Brouillet et al. 2010+).

Habitat and Crop Association :

Habitat et Cultures Associées :

Apera spica-venti grows in cultivated fields, lawns, roadsides and waste places (Barkworth et al. 2007). In southwestern Ontario Canada, and Central and Eastern Europe this species has become a serious weed of winter cereals and winter rapeseed (Warwick et al. 1985; Bitarafan and Andreasen 2020). A. spica-venti is a common weed contaminant found in Poa pratensis (Kentucky bluegrass) seed grown in Oregon, United States (Alderman et al. 2013).

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


In parts of Europe and Canada, Apera spica-venti has caused significant reductions in crop yields (Warwick et al. 1985). Some European populations of A. spica-venti are reported to be herbicide resistant (Heap 2021). Spread occurs entirely by the seeds, which are small and light, and easily spread by wind, water, and combine harvesters (Warwick et al. 1985). A. spica-venti is reported to produce between 2,000 and 16,000 seeds per plant (Bitarafan and Andreasen 2020, Luneva 2021, Warwick et al. 1985).


Apera spica-venti infestation (Barbara Tokarska-Guzik, University of Silesia, Bugwood.org)



  • Spikelet


    • Spikelet length: 2 – 2.8 mm (Barkworth et al. 2007).


    • Glumes lance (teardrop) shaped.

    Surface Texture

    • Spikelet surface smooth or granular.


    • Spikelet green or purplish in colour when fresh (Barkworth et al. 2007).

    Other Features


    • Glumes have stiff-short hairs along the upper half of the keel.

    Other features

    • Spikelet has a single floret that disarticulates below the floret and the glumes remain attached to the plant.
    • Spikelet is not a natural dispersal unit
  • Floret


    • Floret length: 1.8 – 2.6 mm long; width: 0.3 – 0.6 (D. Meyer*).
    *Note: minimum and maximum of 10 spikelets (CDA-S-21714) in a normal range of this species using image measurement (ISMA 2020).
    • Floret length: 2.5 – 3.1 mm; width: 0.3 – 0.5 mm (CFIA**).
    **Note: minimum and maximum of 20 florets in a normal range of this species using image measurement protocol (ISMA 2020).

    Additional size information from literature:

    • Floret length: 2.0 – 2.5 mm long ca. 0.5 mm wide (Musil 1963).
    • Floret length: 1.6 – 3.0 mm long (Barkworth et al. 2007).
    • Floret length: 1.5 – 2.5 mm long (Baldwin et al. 2012).
    • Floret length: 2.5 – 3.0 mm long (Tutin et al. 1980).


    • Floret shape is a narrower teardrop, tapering to an awned end; slightly dorsal-ventrally compressed.

    Surface Texture

    • Floret surface is smooth or granular with short stiff hairs on the upper one-half to two-thirds of the lemma.


    • Floret is medium or light brown.

    Other Features


    • The lemma margins are in-rolled concealing the edges of the palea.

    Lemma Awn

    • The awn is attached slightly below the tip of the lemma and is straight and thin.
    • Awn length: 4.3 – 7 mm long, average 5.6 mm (D. Meyer*).
    *Note: minimum and maximum based on 10 florets (CDA-S-21714) in a normal range of this species using image measurement protocol (ISMA 2020).
    • Awn length: 4.6 – 9.8 mm, average 7.3 mm (CFIA**).
    **Note: minimum and maximum based on 20 florets in a normal range of this species using image measurement protocol (ISMA 2020).

    Additional size sources from literature:
    • Awn length: 6 – 10 mm long (Musil 1963).
    • Awn length: 5 – 12 mm long (Barkworth et al. 2007).
    • Awn length: 4 – 9 mm long (Baldwin et al. 2012).
    • Awn length: 5 – 12 mm long (Tutin et al. 1980).


    • The palea is +/- equal in length to the lemma.


    • Rachilla is short, thin, and wire-like, ca. 0.5 mm long (Barkworth et al. 2007).


    • Callus on palea side of floret is horseshoe-shaped and glabrous or with stiff white hairs on either side of rachilla.
    • Point of attachment of the callus is oval (located on palea side of floret).
    • Callus on lemma side is a blunt, narrow ridge with or without long hairs above the ridge.
  • Caryopsis


    • Caryopsis length: 1.0 – 1.5 mm long (Barkworth et al. 2007), about 0.5 mm wide.


    • Caryopsis oblong-shaped, longitudinally grooved on ventral surface.

    Surface Texture

    • Caryopsis surface smooth and glabrous.


    • Caryopsis colour reddish yellow.

    Other Features


    • Hilum basal, egg-shaped.

    Style base

    • Style base usually remaining attached at apex.
  • Embryo



    • Embryo partially fills about one-third the length of the caryopsis.


    • Embryo linear, lateral position.


    • Endosperm translucent yellow, soft, or semi-liquid.

Identification Tips


Apera spica-venti and A. interrupta are very similar in floret size; however, the awn of A. interrupta tends to be longer. The key point of separation of the two species is the length of the anther (usually less than 0.5 mm for A. interrupta and 1 – 2 mm for A. spica-venti, Barkworth et al. 2007). Apera can also be confused with Agrostis but distinguished from Agrostis in most cases by the length of the palea and the presence of a rachilla (palea nearly equal to the lemma length and wire-like rachilla present for Apera; palea absent or if present much shorter than the lemma and rachilla absent for Agrostis).

Additional Botany Information



  • Anthers 1 – 2 mm long (Barkworth et al. 2007) (important character distinction from A. interrupta, in which the anthers are 0.5 mm or less in length).
  • The inflorescence is an open, pyramid-shaped panicle, each branch without spikelets for about 5 mm from base (Barkworth et al. 2007).
  • The single floret spikelets disarticulate above the glumes; the floret is the dispersal unit and the glumes remain attached to the plant.

Vegetative Features

  • Plants form stout tufts of several stems, 20 – 120 cm tall (Barkworth et al. 2007).

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.


Apera interrupta (L.) P. Beauv. (interrupted windgrass)

Annual; native to Europe, grows in lawns, roadside, sandy open ground and Triticum aestivum subsp. aestivum (winter wheat) fields (Barkworth et al. 2007). Apera interrupta florets have a similar lance-shape, awned lemma, granular surface texture and hairs on the upper portion of lemma and above callus as in A. spica-venti; however, A . interrupta florets are generally smaller, 1.7 – 2.3 mm long, average length 2 mm; 0.3 – 0.5 mm wide, average width 0.42 mm (D. Meyer*) and the awns are longer, 5 – 9.7 mm or more long, average length 7 mm (D. Meyer*); anther length 0.3 – 0.5 mm (Barkworth et al. 2007).

Other features: The inflorescence of A. interrupta is narrow with the branches erect, and each branch of the inflorescence is covered by spikelets to near the base, compared to the open, pyramid-shaped panicle without spikelets near the branch base of A. spica-venti (Barkworth et al. 2007).

*Note: minimum and maximum based on 30 florets (CDA-S-21713, n=10; CDA-S-21712, n=20) in a normal range of this species using image measurement protocol (ISMA 2020).

Additional size information from literature:
• Floret length: 2 – 2.5 mm long; Awn length: 4 – 10 mm long; Anther length 0.3 – 0.4 mm long (Tutin et al. 1980)

• Floret length: 1.5-2 mm long; Awn length: 5 – 8 mm; Anther length 0.3 – 0.5 mm (Baldwin et al. 2012).


Agrostis canina (velvet bent grass)

Perennial; native to temperate Europe and Asia, grows in roadsides and open ground, also used as a lawn grass (Barkworth et al. 2007). Agrostis canina has a similar shape to that of A. spica-venti; however, the floret is smaller, 1.0 – 1.6 mm long and 0.3 – 0.5 mm wide (CFIA**), the lemma has a smooth surface, the awn is bent and attached near mid-lemma or lower when present, the palea is absent or highly reduced, the rachilla is absent, and the lemma is translucent whitish coloured.

** Note: minimum and maximum of 20 florets in a normal range of this species using image measurement protocol (ISMA 2020)

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Alderman, S. C., Elias, S. G., and Hulting, A. G. 2013. Occurrence and Trends of Weed Seed and Ergot Contaminants in Oregon Grown Poa pratensis and Poa trivialis Seed Lots. Seed Technology 35(2), 237–250.

Association of Official Seed Analysts (AOSA). 2021. AOSA Rules For Testing Seeds. Volume 3: Uniform Classification of Weed and Crop Seeds. AOSA, Washington, DC.

Baldwin, B. G, Goldman, D., Keil, D. J., Patterson, R., Rosatti, T. J., and Wilken, D. (Eds.). 2012. The Jepson Manual : Vascular Plants of California. 2nd Ed. University of California Press, Berkeley, CA.

Barkworth, M. E., Capels, K. M., Long, S. and Piep, M. B. (eds.). 2007. Flora of North America Volume 24. Magnoliophyta: Commelinidae (in part): Poaceae, part 1. Oxford University Press, New York, New York.

Bitarafan, Z. and Andreasen, C. 2020. Seed production and retention at maturity of blackrass (Alopecurus myosuroides) and silky windgrass (Apera spica-venti) at wheat harvest. Weed Sci. 68:151-156. doi: 10.1017/wsc.2020.7

Brouillet, L., Coursol, F., Meades, S. J., Favreau, M., Anions, M., Bélisle, P. and Desmet, P. 2010+. VASCAN, the database of vascular plants of Canada. http://data.canadensys.net/vascan/ Accessed December 8, 2021.

Darbyshire, S. J. 2003. Inventory of Canadian Agricultural Weeds. Agriculture and Agri-Food Canada, Research Branch. Ottawa, ON.

Global Biodiversity Information Facility (GBIF) Secretariat. 2022. https://doi.org/10.15468/39omei Accessed via https://www.gbif.org/species/5289642 Accessed December 29, 2022.

Heap, I. 2021. Herbicide Resistant Silky Windgrass Globally (Apera spica-venti). The International Survey of Herbicide Resistant Weeds.  www.weedscience.com Accessed December 8, 2021.

Ikeda, T., Iwasaki, K., Suzuki, T., Wong, L. J., Pagad, S. 2021. Global Register of Introduced and Invasive Species- Japan. Version 1.2. Invasive Species Specialist Group ISSG. Checklist dataset https://doi.org/10.15468/nt2yla accessed via GBIF.org on 2021-12-08.

International Seed Morphology Association (ISMA). 2020. Method for Seed Size Measurement. Version 1.0. ISMA Publication Guide. https://www.idseed.org/authors/details/method_for_seed_size_measurement.html

Luneva, N. N. 2021. Apera spica-venti (L). Beauv. Silky Bentgrass, Wind-Grass. In A.N.Afonin,S.L. Greene, N.I. Dzyubenko, A.N. Frolov (eds.). 2008. Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. Economic Plants and their Diseases, Pests and Weeds [Online]. Available at: http://www.agroatlas.ru/en/content/related/Apera_spica-venti/ Accessed December 8, 2021.

Musil, A. F. 1963. Identification of Crop and Weed Seeds: Agriculture Handbook No. 219. U. S. Department of Agriculture, Agricultural Marketing Service, Washington D. C.

Tutin, T. G., Heywood, V. H., Gurges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M., Webb, D. A. (Eds.). 1980. Flora Europaea, Vol. 5 : Alismataceae to Orchidaceae (Monocotyledones). Cambridge University Press.

U.S. Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS). 2016. Weed Risk Assessment for Apera spica-venti (L.) P. Beauv. (Poaceae) – Common Windgrass. Version 1. U. S. Dept. of Agriculture, Animal and Plant Health Inspection Service.

U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). 2021. Germplasm Resources Information Network (GRIN Taxonomy). National Germplasm Resources Laboratory, Beltsville, Maryland. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomydetail?id=3681. Accessed November11, 2021.

U.S. Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2021. The PLANTS Database http://plants.usda.gov National Plant Data Team, Greensboro, NC USA. Accessed November11, 2021.

U.S. Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2022. The PLANTS Database. National Plant Data Team, Greensboro, NC USA. http://plants.usda.gov Accessed December 29, 2022.

U.S. Department of Agriculture- Phytosanitary Certificate Issuance and Tracking System- Phytosanitary Export Database (USDA-PCIT-PExD). 2021. Phytosanitary Export Database (PExD) System. PExD contains phytosanitary import requirements of U.S.-origin commodities to foreign countries. https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp. Accessed November 11, 2021.

Walsh, N. G. 2020. Apera interrupta, in (ed.), Flora of Australia. Australian Biological Resources Study, Department of Agriculture, Water and the Environment : Canberra. https://profiles.ala.org.au/opus/foa/profile/Apera%20interrupta Accessed December 7, 2021.

Warwick, S. I., L. D. Black, and B. F. Zilkey. Biology of Canadian Weeds.: 72. Apera spica-venti. Canadian Journal of Plant Science. 65(3): 711-721. https://doi.org/10.4141/cjps85-091

Wiersema, J. H. and B. León. 1999. World Economic Plants: A Standard Reference. CRC Press, Boca Raton, FL.



Jennifer Neudorf ¹, Deborah J. Lionakis Meyer ², Angela Salzl ¹, Ruojing Wang ¹, Karen Castro ¹, Katrina Entwistle ¹

¹ Canadian Food Inspection Agency and,

² California Department of Food & Agriculture (retired)