Fact Sheets


Family :

Famille :


Synonym(s) :

Synonyme(s) :

Common Name(s) :

Nom(s) commun(s) :


(English) (GC 2016; FNA 2022; USDA-ARS 2022)
Patience (French) (GC 2016)
Sorrel (English) (FNA 2022; USDA-ARS 2022)

  • Curled dock (Rumex crispus) achenes and perianths

  • Curled dock (Rumex crispus) achene

  • Bitter dock (Rumex obtusifolius) achenes

  • Bitter dock (Rumex obtusifolius) achene

  • Bitter dock (Rumex obtusifolius) achene; top-down view

  • Field dock (Rumex pseudonatronatus) achenes and perianths

  • Field dock (Rumex pseudonatronatus) achene

  • Dock (Rumex sp.) seed, cross section

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Regulation :

Remarques Réglementation:

  • CFIA Weed Seeds Order - Class 3: Secondary Noxious Weed Seeds
  • USA Federal Noxious Weed List
  • USA Federal Noxious Weed Seed List

Regulation Notes:

  • Secondary Noxious, Class 3 in the Canadian Weed Seeds Order (2016) under the Seeds Act, with the exception of Rumex maritimus and R. acetosella.
  • Federal Noxious Weed List (Rumex hypogaeus T. M. Schust. & Reveal and R. spinosus L. only)

Distribution :

Répartition :

The Rumex genus is made up of 190-200 species worldwide, both native and introduced to regions generally with a temperate climate (FNA 1993+). Species adapted to disturbance, such as R. crispus and R. obtusifolius, have spread worldwide with anthropogenic activity, and adapted to conditions not found in their original habitats (Cavers and Harper 1964).

The genus is widespread in the United States and Canada, 63 species are recorded in North America north of Mexico (FNA 1993+), including over 30 species native to North America (USDA-NRCS 2022). Rumex species occur in all Canadian provinces and territories with 33 species and 3 hybrid species recorded (Brouillet et al. 2010+).

Habitat and Crop Association :

Habitat et Cultures Associées :

Rumex species grow well on a large range of soil types, except for acidic soils and peat, and can be found growing up to 3500 metres above sea level (Zaller 1982). R. crispus and R. obtusifolius are prominent weeds of agriculture, invading pastures, cultivated fields, disturbed soils and mismanaged agricultural land (Cavers and Harper 1964; Zaller 1982; Darbyshire 2003).

The majority of the literature about Rumex species highlights R. crispus and R. obtusifolius. R. crispus is considered one of the 12 most successful worldwide weeds, infesting 16 crops in 37 countries (Holm et al. 1991). R. crispus seed is a common impurity in Trifolium spp. (clovers), Medicago sativa (alfalfa, lucerne), Avena sativa (oats), Triticum aestivum subsp. aestivum (wheat), Hordeum vulgare (barley) and grass seed (Cavers and Harper 1964). R. obtusifolius plants are found in disturbed ground, field edges and mismanaged grassland (Cavers and Harper 1964; FNA 1993+).

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:

Annual, biennial or perennial

Dispersal Unit Type :

Type d’unité de dispersion :


General Information


Rumex species occur on every continent, in a large variety of soil types: standing water, salt water, sand, gravel, clay, loam and chalk; species appear to be most successful in disturbed areas (Darbyshire 2003; Bojňanský and Fargašová 2007). Certain species have been introduced with anthropogenic activity outside of their native areas and can become agricultural pests that lower quality of grain and forage (Cavers and Harper 1964; Hume and Cavers 1982). Rumex species may also have medicinal or culinary uses, including R. crispus and R. acetosella (Cavers and Harper 1964; Stopps et al. 2011). Rumex plants and seeds may be toxic to livestock and poultry due to oxalates, rumicin and chrysorobin produced by the plants (Holm et al. 1991; Stopps et al. 2011).

Rumex species reproduce primarily by seed, specifically an achene dispersed inside a perianth. Cavers and Harper (1964) estimated that between 100 – 40 000 seeds can be produced by one plant of R. crispus and 100 – 60 000 seeds by R. obtusifolius in one year. Achenes enclosed in a perianth can be dispersed by the wind, catch in animal fur or human clothing or float on the water supported by the tubercles (Cavers and Harper 1964). Achenes can be eaten by birds and animals and remain viable after digestion (Cavers and Harper 1964; Holm et al. 1991).

Rumex achenes can also contaminate crop seed and be introduced to new areas during planting (Cavers and Harper 1964). Buried seeds of R. crispus have been found viable after 80 years, R. obtusifolius and R. salicifolius seed remained viable after 40 years of burial (Toole 1946; Darlington and Steinbauer 1961). There is evidence that R. crispus and R. obtusifolius can reproduce vegetatively from root fragments, but it appears to be restricted to the main taproot or only at the beginning of the growing season (Cavers and Harper 1964). Reduced below-ground herbivore damage to introduced populations of R. crispus, R. obtusifolius and R. conglomeratus compared to native ranges likely enhances the invasive ability of these species (Costan et al. 2022).

Rumex crispus, R. obtusifolius, R. acetosa and R. acetosella are some of the Rumex species that have been divided into subspecies (USDA-ARS 2022). These subdivisions are from morphological and/or ecological differences from genetic adaptation to their local habitats (FNA 1993+). These subspecies and local forms mix when they are introduced into new areas, creating intermediate forms (Hume and Cavers 1982; FNA 1993+). Hume and Cavers (1982) sampled R. crispus from locations where it was native and introduced. They found that a higher percentage of genetic variability occurred within plants of a population than between different locations. Most of the variability was found between the plants, and this was explained by an inherent flexibility to local conditions, preserved by self-fertilization.

Hybrids between R. crispus and other Rumex species have been documented, occurring due to distribution overlap or both species introduced to a new location. The hybrid of R. crispus and R. obtusifolius is well documented, and is known as Rumex × pratensis Mertens & Koch (Cavers and Harper 1964; FNA 1993+). Other documented hybrids in Canada include R. × alexidus B. Boivin (R. maritimusR. stenophyllus) and R. × franktonis B. Boivin (R. pseudonatronatusR. triangulivalvis) (Brouillet et al. 2010+).




  • Perianth


    Perianth covering achenes of Rumex species are generally medium-sized (length: 3– 6 mm), but species have a range of perianth sizes (from FNA 1993+):

    • Small-sized perianth species, e.g. Rumex acetosella length: 1.2 – 1.7 mm; width: 0.5 – 1.3 mm
    • Medium-sized perianth species, e.g. Rumex crispus length: 3.5 – 6 mm; width: 3 – 5 mm
    • Large-sized perianth species, e.g. Rumex britannica length: 4 – 7 mm; width 3.5 – 7 mm


    • Perianth generally triangular shaped, can be egg-shaped or almost globose
    • Perianth edges variable, entire, wavy or with narrow lobes (teeth)

    Surface Texture

    • Perianth surface textured with a network of raised veins
    • Each tepal generally with an oval, spongy tubercle in the centre, the size varies with the species


    • Perianths are generally reddish brown when mature, green or pinkish when immature
    • Tubercles generally light brown or reddish-brown when mature, light green, green, pinkish or red when immature

    Other Features

    • Tepals (also called valves) are in 2 series: 3 small, triangular-shaped outer tepals and 3 large inner tepals, used in species identification
    • Rumex species perianths have a papery consistency
  • Achene


    Achenes of Rumex species are generally medium-sized (length 2 – 3 mm), but the genus contains achenes in a range of sizes (from FNA 1993+):

    • Small-sized achene species, e.g. Rumex acetosella length: 0.9 – 1.5 mm; width: 0.6 – 0.9 mm
    • Medium-sized achene species, e.g. Rumex crispus length: 2 – 3 mm; width: 1.5 – 2 mm
    • Large-sized achene species, e.g. Rumex britannica length: 3 – 4.5 mm; width: 1.5 – 2.5 mm


    • Achenes of Rumex species are oval or egg-shaped, trigonous in 3D, edges keeled or rounded with generally one short-pointed and one long-pointed end

    Surface Texture

    • Surface texture is generally smooth, but under 60x magnification minute pitting may be visible


    • Achenes of Rumex species are generally shiny reddish-brown, but can be light, medium or dark brown coloured

    Other Features

    • Achenes of Rumex spp. are shed within a perianth that is generally removed during processing
    • Achenes of some Rumex species may be dimorphic: R. crispus was found to have heavier achenes near the main stem and lighter ones at the ends of branches (Cavers and Harper 1964)
  • Seed


    • Seed size similar to achene size


    • Seed is trigonous with one end truncate, other pointed

    Surface Texture

    • Surface is smooth


    • Seed coat is dark reddish or brownish coloured

    Other Features

    Hilum and hilum area

    • Hilum is not visible
  • Embryo


    • Embryo partially fills the seed


    • Embryo is linear and curved (Martin 1946)


    • Endosperm is hard and translucent white coloured

    Other Features

    • Embryo is in a peripheral position

Identification Tips


Disseminules of Rumex species have features that distinguishes them within the Polygonaceae. These include:

• Achenes strongly trigonous, pointed at one or both ends
• Shiny reddish-brown or brown colour
• Smooth surface texture
• Persistent perianth of 5-6 reddish-brown tepals in 2 series (may be removed during seed processing)
• Inner tepals with or without a spindle-shaped, spongy tubercle
• Embryo peripheral, situated along a flat side of the seed

The perianth has features useful for identification to the species level, but is generally removed during commercial processing. The achene shape and colour is similar among most Rumex species, and can be challenging to identify.

Additional Botany Information



  • Inflorescence is generally a stem at the top of the plant with several clusters of flowers
  • Generally 4 – 30 flowers per cluster (FNA 1993+)
  • Flower petals similar, in 2 series, with the outer tepals small, and the inner tepals large, triangular shaped, with a veiny texture
  • The perianth is shed with the fruit, covering the achene, generally with a spongy tubercle in the centre of each tepal (FNA 1993+)
  • Flowers are wind-pollinated, they do not have nectar, but some insects collect pollen from them (Cavers and Harper 1964)

Vegetative Features

  • Plants may grow erect or prostrate along the ground (FNA 1993+)
  • Each branch and flower cluster is associated with fused bracts called ocrea, characteristic of the Polygonaceae (FNA 1993+)
  • Leaves are variably shaped among the species: ovate, almost spherical or linear, with smooth, wavy or lobed edges (FNA 1993+)

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.

The achenes of Rumex species have similar features that can be difficult to distinguish to the species level; intact perianths provide more information, but identification features may overlap and are confused further by variable morphology and hybridization. Two species that are excepted from the Canadian Weed Seeds Order (2016), R. acetosella and R. maritimus, can be distinguished from other Rumex species.

• Achenes of R. acetosella are a smaller size than other Rumex species and have rounded edges. The perianth fits tightly to the achene, does not have narrow lobes (teeth) along the edges and lacks tubercles.
• Achenes of R. maritimus are pointed at both ends, medium-brown and smaller than commonly encountered species. The perianth has distinctive long teeth on the edges.

Features of Rumex species achenes and perianths can be compared to aid in identification. Emphasis is on the species which are exceptions in Canadian regulation, commonly encountered as crop impurities, and widespread in North America, Asia or Europe (FNA 1993+; GBIF Secretariat 2022). Measurement ranges and feature descriptions are combined from Flora of North America (FNA 1993+) and Bojňanský and Fargašová (2007).

Achene length Achene width Perianth length Perianth width Perianth edge # tubercles
Subgenus Acetosa
R. acetosa L. 1.8-2.5 mm 1.2-1.5 mm 3-4 mm 3-4 mm smooth 0
Subgenus Acetosella
R. acetosella L. 0.9-1.5 mm 0.6-0.9 mm 1.2-1.7 mm 0.5-1.3 mm smooth 0
Subgenus Rumex
R. maritimus L. 0.9-1.9 mm 0.6-1 mm 2.5-3 mm 0.75-2 mm toothed 3
R. conglomeratus Murray 1.5-1.8 mm 1-1.4 mm 2-3.8 mm 1-2.3 mm smooth 3
R. crispus L. 1.9-3 mm 1.2-2 mm 3.5-6 mm 3-5 mm smooth 3
R. obtusifolius L. 2-2.7 mm 1.2-1.7 mm 3-7 mm 2-4 mm toothed 1
R. pulcher L. 2-2.8 mm 1.3-2 mm 3-6 mm 2-4 mm toothed 3
R. pseudonatronatus (Borbás) Murb. 2-3.3 mm 1-1.7 mm 3.5-7.4 mm 3-6.2 mm smooth 0
R. stenophyllus Ledeb. 2-3.3 mm 1-1.9 mm 3.5-5 mm 3-5 mm toothed 1 or 3
R. longifolius DC. 2.2-3.5 mm 1.3-2 mm 4.3-6 mm 3.6-7 mm smooth 0
R. aquaticus L. 2.7-3.5 mm 1.3-1.7 mm 6-8 mm 4-5 mm smooth 0

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Bojňanský V. and Fargašová, A. 2007. Atlas of Seeds and Fruits of Central and East-European Flora. Springer, The Netherlands. 1046 pp.

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 November 07, 2022.

Cavers, P.B. and Harper, J.L. 1964. Rumex obtusifolius L. and R. crispus L. Journal of Ecology, 52:737-766.

Costan, C-A., Godsoe, W.K., Bufford, J.L., Marris, J.W.M., Hulme, P.E. 2022. Can the enemy release hypothesis explain the success of Rumex (Polygonaceae) species in an introduced range? Biological Invasions 24:2665–2677.

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

Darlington, H. T. and Steinbauer, G. P. 1961. The eighty-year period for Dr. Beal’s seed viability experiment. American Journal of Botany 48: 321-325.

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 November 07, 2022.

Global Biodiversity Information Facility (GBIF) Secretariat. 2022. https://doi.org/10.15468/39omei Accessed via https://www.gbif.org/species/2888942 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. 1991. The World’s Worst Weeds: Distribution and Ecology. Krieger Publishing Company, Florida. 609 pp.

Hume, L., and Cavers, P.B. 1982. Geographic variation in a widespread perennial weed, Rumex crispus. The relative amounts of genetic and environmentally induced variation among populations. Canadian Journal of Botany 60: 1928- 1937.

Martin, A.C. 1946. The comparative internal morphology of seeds. The American Midland Naturalist 36: 513-660.

Stopps, G.J., White, S.N., Clements D.R., and Upadhyaya, M.K. 2011. The Biology of Canadian weeds. 149. Rumex acetosella L. Can. J. Plant Sci. 91: 1037-1052.

Toole, E. H. 1946. Final results of the Duvel buried seed experiment. Journal of Agricultural Research 72: 201-210.

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 November 10, 2022.

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.

Zaller, J.G. 2004. Ecology and non-chemical control of Rumex crispus and R. obtusifolius (Polygonaceae): a review. Weed Research 44: 414–432.



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