Fact Sheets


Lythrum salicaria L.

Family :

Famille :


Synonym(s) :

Synonyme(s) :

Lythrum salicaria L. subf. anceps Koehne                         (POWO 2022; USDA-ARS 2022)
Lythrum salicaria L. var. anceps (Koehne) Koehne           (USDA-ARS 2022)
Lythrum anceps (Koehne) Makino                                     (POWO 2022; Tropicos 2022)
Lythrum argyi H.Lév.                                                          (CABI 2022; POWO 2022; Tropicos 2022)
Lythrum tomentosum Mill. (POWO 2022; Tropicos 2022)

Common Name(s) :

Nom(s) commun(s) :

Purple loosestrife

(English) (GC 2016; CABI 2022; USDA-ARS 2022)
Salicaire commune (French) (GC 2016; Darbyshire 2003; CABI 2022)
Spiked loosestrife (English) (CABI 2022; Tropicos 2022; USDA-ARS 2022)
Lysimaquia roja (Spanish) (CABI 2022)
Abre-o-sol (Portuguese) (CABI 2022)


  • Purple loosestrife (Lythrum salicaria) seeds

  • Purple loosestrife (Lythrum salicaria) seeds

  • Purple loosestrife (Lythrum salicaria) seed, inner side

  • Purple loosestrife (Lythrum salicaria) capsule and seed

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Regulation :

Remarques Réglementation:

  • CFIA Weed Seeds Order - Class 2: Primary Noxious Weed Seeds
  • USA Federal Noxious Weed Seed List

Regulation Notes:

Distribution :

Répartition :

Native to northern Africa, Europe, and temperate Asia and introduced in North America, Chile, South Africa, Australia and New Zealand (Mal et al. 1992; USDA-ARS 2022). It is found throughout the United States except for the extreme southeastern states; abundant in the northeastern region (Kartesz 2011). Occurs in all Canadian provinces but not in the Territories (Brouillet et al. 2010+).

Habitat and Crop Association :

Habitat et Cultures Associées :

Grows in pastures, meadows, old fields, gardens, wetlands, shores, and disturbed areas (Darbyshire 2003). Not usually a weed of agriculture but can grow along field edges near wetlands (CABI 2022). This species is adapted to wet soils near streams, lakes, and wetlands, and is generally associated with Typha spp. (cattails) (Mal et al. 1992).

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


Lythrum salicaria has been present in North America since the early 19th century, likely first introduced in ship ballast (Mal et al. 1992). It may also have been planted as a medicinal herb, or brought by beekeepers as a source of nectar (Mal et al. 1992). It is available from some seed companies as an ornamental (CABI 2022).

The plants have a high seed production with each stem of the plant producing 900-1000 capsules, and the average seed production of 2.7 million seeds per plant (Mal et al. 1992). The seeds are generally dispersed by water, and can adhere to animals or vehicles (Mal et al. 1992).

Seeds remain viable after 2 to 3 years submerged in water, and 400,000 seeds were estimated in wetland top soils in Minnesota, United States (Mal et al. 1992). Disturbed sites with moist soils or seasonally flooded sites are required for establishment (CABI 2022).


Lythrum salicaria infestation (Agriculture and Agri-Food Canada , Agriculture and Agri-Food Canada, Bugwood.org)



  • Capsule


    • Capsule length: 3 – 4 mm; width: 2 mm (Mal et al. 1992)


    • Capsule is oblong or egg-shaped (Mal et al. 1992)

    Surface Texture

    • Capsule surface is smooth
    • The surface appears hairy with longitudinal nerves from the persistent calyx covering the capsule


    • Capsule is brown coloured

    Other Features

    • Capsule remains enclosed in the calyx at maturity
    • Capsule splits into 2 valves to release the seeds (Mal et al. 1992)
  • Seed


    • Seed length*: 0.7 – 1.0 mm; width: 0.3 – 0.5 mm
    *Note: minimum and maximum of 10 seeds in a normal range of this species using image measurement (ISMA 2020)


    • Seed shape is variable: teardrop, wedge-shaped, or oval

    Surface Texture

    • Seed surface with thin longitudinal striations, giving a sparkling look to the seed


    • Seed generally dark red or reddish-brown, darker reddish-brown at the hilum end or both ends

    Other Features

    Hilum and hilum area

    • Hilum is a black dot at the wide end of the seed

    Other than hilum

    • A raphe (thin ridge) extends from the hilum to the narrow end of the seed
  • Embryo


    • Embryo fills the seed


    • Embryo is spatulate, axial position


    • Endosperm is scant, nutritive tissue stored in cotyledons

Identification Tips


Seeds of the Lythraceae can be recognized by their small size, the plano-convex shape in edge view, surface with dense longitudinal striations, small hilum near one end and longitudinal raphe on the flat side of the seed. Seed shape in this family is generally round and straw yellow coloured, but those of Lythrum salicaria are variable shaped and generally reddish-brown coloured.

Additional Botany Information



  • Flower length: 5-12.5 mm (Mal et al. 1992)
  • Flowers pinkish-purple coloured
  • Calyx fused into a tube, length: 3.5-9.0 mm (Mal et al. 1992)
  • Calyx purplish when flowering, turning brown when capsule is mature

Vegetative Features

  • Leaves are 3 – 10 cm long, sessile, arranged opposite or in whorls of three in the lower part of the plant and alternate in upper sections (Mal et al. 1992)
  • Plants may be 0.5 to 2.7 m in height

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.

Lythrum hyssopifolia L. (hyssop loosestrife)

L. hyssopifolia, a wetland species native to Europe, is established in North America along Atlantic and Pacific coastal United States and recently in the Great Lakes region (Blaney et al. 1997). The seeds (length*: 0.7 – 1.0 mm; width: 0.5 – 0.7 mm) are generally wider, egg-shaped, and straw-yellow coloured compared L. salicaria.

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

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Blaney, C.S., Oldham, M.J. , and Reznicek, A.A. 1997. Hyssop-leaved Loosestrife, Lythrum hyssopifolia L. (Lythraceae), New to Canada. Canadian Field-Naturalist 111: 664-665.

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 April 29, 2021.

Centre for Agriculture and Bioscience International (CABI). 2022. Invasive Species Compendium, CAB International, Wallingford, UK. https://www.cabidigitallibrary.org/journal/cabicompendium Accessed December 29, 2022.

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

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

Global Biodiversity Information Facility (GBIF) Secretariat. 2022. https://doi.org/10.15468/39omei Accessed via https://www.gbif.org/species/3188736 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)

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

Kartesz, J. T. 2011. The Biota of North America Program (BONAP). North American Plant Atlas. Chapel Hill, N.C., www.bonap.org/MapSwitchboard.html Accessed May 30, 2016.

Mal, T. K., Lovett-Doust, J., Lovett-Doust, L. and Mulligan, G. A. 1992. The biology of Canadian weeds. 100. Lythrum salicaria. Canadian Journal of Plant Science 72: 1305-1330.

Plants of the World Online (POWO). 2022. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/  Accessed March 30, 2022.

Tropicos.org. 2022. Missouri Botanical Garden. https://tropicos.org Accessed March 30, 2022.

U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). 2022. Germplasm Resources Information Network (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysimple.aspx Accessed December 29, 2022.



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