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Ageratum houstonianum Mill.

Overview
General Information
ID Info
Similar Species
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Aperçu
Renseignements Généraux
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Family :

Famille :

Asteraceae

Synonym(s) :

Synonyme(s) :

Ageratum conyzoides var. mexicanum (Sims) de Candolle (FNA 1993+)
Ageratum mexicanum (USDA-ARS 2023)

Common Name(s) :

Nom(s) commun(s) :

Bluemink

(English) (FNA 1993+; USDA-ARS 2023)
Ageratum du Mexique (French) (UPOV 2011+; USDA-ARS 2023)
Xiong er cao 熊耳草 (Chinese) (FOC 1994+; USDA-ARS 2023)
Agérato (Spanish) (UPOV 2011+; USDA-ARS 2023)

Ageratum houstonianum achenes

  • Ageratum houstonianum achenes

  • Ageratum houstonianum achenes

  • Ageratum houstonianum achene

  • Ageratum houstonianum achene

  • Ageratum houstonianum achene base

  • Ageratum houstonianum pappus

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Overview

Aperçu

Regulation :

Remarques Réglementation:

    Regulation Notes:

    Distribution :

    Répartition :

    Ageratum houstonianum is native to southeastern Mexico and Central America (Holm et al. 1991; FNA 1993+) and is cultivated as an ornamental in areas outside the native range, e.g., the United Kingdom and northern Europe (Johnson 1971; CABI 2022). This species has been found outside of cultivation in Africa, China, Nepal, Southeast Asia, India, France, and Australia (CABI 2022).

    Introduced populations in North America are likely established from garden cultivars (FNA 1993+). Naturalized populations have been recorded in the United States in Hawai’i, the southeast, along the east coast, as well as in the Caribbean. A. houstonianum has not been recorded in Canada (Brouillet et al. 2010+; USDA-NRCS 2023).

     

    Habitat and Crop Association :

    Habitat et Cultures Associées :

    Ageratum houstonianum was found to establish readily in disturbed areas, especially humid habitats, e.g., coasts, wetlands, waterways, and riparian zones (FNA 1993+; CABI 2022). It has also been recorded growing in pastures, crops, roadsides, shrublands, and forest openings (CABI 2022). The species is rapidly invading forest openings in national parks in Nepal (Bhatta et al. 2020). It has been recorded as a weed in Saccharum officinarum (sugarcane), Nicotiana tabacum (tobacco), Macrotyloma uniflorum (horse gram), Vigna angularis (adzuki bean), Vigna mungo (mung bean), Camellia sinensis (tea), Cinchona spp. (cinchona) and Coffea arabica (coffee) (Holm et al. 1991; Bist and Shretha 2022; CABI 2022).

    Economic Use, cultivation area, and Weed Association :

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

    Ageratum houstonianum is cultivated as an ornamental plants in many part of the world (Johnson 1971; CABI 2022; UPOV 2011+).

    Duration of Life Cycle :

    Durée du cycle vital:

    Annual

    Dispersal Unit Type :

    Type d’unité de dispersion :

    Achene

    General Information

    RENSEIGNEMENTS GÉNÉRAUX

    Ageratum houstonianum seeds from coastal Mexico were planted in Europe as a garden plant in the mid 1700s, and the ability to invade adjacent areas was noticed soon after (Johnson 1971). In the United Kingdom and northern Europe, the plant does not appear to invade areas outside of gardens, likely due to low temperatures (CABI 2022).

    Ageratum houstonianum is an annual species reproducing by seeds only, but can sprout from prostrate stems in suitable habitat (Barua et al. 2013). Data are lacking on the amount of seed produced each year, but 30,000-40,000 seedlings per square metre were observed in Assam (Barua et al. 2013).

    Lamsal et al. (2019) found that seed germinated on or near the soil surface, and did not emerge when planted 2mm or deeper. Stored seed is viable for only one year, but the similar species A. conyzoides has remained viable for up to three years (Stephens 2007; Lamsal et al. 2019). Dispersal vectors of the light A. houstonianum seed are primarily wind and water, but they may stick to animals, clothing, vehicles and contaminated soil or produce (Stephen 1971; CABI 2022).

    A. houstonianum invasions were documented in Nepal and Assam, India (Johnson 1971; Barua et al. 2013; Lamsal et al. 2019). The species was widespread in a national park in Nepal, and was not found in a survey a decade prior (Bhatta et al. 2020). It had the highest biomass and dominated the weed community of legume fields (Bist and Shrestha 2022). In Assam, A. houstonianum has been observed in almost all crops, and characterized as an aggressive colonizing weed of disturbed areas (Barua et al. 2013). Acute toxicity of this species to livestock has been confirmed; plants are avoided until no other feed is available (Bhatta et al. 2022).

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    Identification

    Identification

    <
    >

    • Achene

      Size

      • Achene length*: 1.4 – 2.4 mm; width: 0.4 – 0.6 mm
      *Note: minimum and maximum of 20 achenes in a normal range of this species using image measurement (ISMA 2020)

      Achene size from literature:
      • Length: 1.5 – 1.75 mm (Johnson 1971; FOC 1994+)
      • Length: 1.5 – 2 mm (Holm et al. 1991)
      • Pappus scale length: 2-3 mm (Johnson 1971; FNA 1993+)

      Shape

      • Achenes are oblong shaped, may be slightly curved longitudinally
      • End with the pappus is truncate, the opposite end can be more narrow
      • Pappus scales are generally wedge shaped, edges are roughly toothed, tapering into a long bristle

      Surface Texture

      • Surface papillate tuberculate with 4-5 longitudinal ridges, scattered hairs on the achene body and on ridges

      Colour

      • Achenes are shiny black, appearing sparkling under strong light
      • Achenes may be dull brown when immature or if the outer layer is abraded
      • Hairs are white or light brown
      • Pappus scales are light yellow or light brown

      Other Features

      • Achene pappus of 5 or more scales, may be removed during seed processing.

      Ageratum houstonianum achenes

    <
    >

    • Seed

      Size

      • Seed size similar to achene size

      Shape

      • Seed is oblong shaped

      Surface Texture

      • Seed surface is smooth

      Colour

      • Seed is light brown coloured

      Other Features

      • Hilum not visible
      • Seed is soft and oily, appears semi-liquid
    <
    >

    • Embryo

      Size

      • Embryo fills the seed

      Shape

      • Embryo spatulate shaped

      Endosperm

      • Nutritive tissue is contained in the cotyledons (Martin 1946)

      Other Features

      • Embryo in axial position

    Identification Tips

    CONSEILS POUR L’IDENTIFICATION

    A. houstonianum belongs to the Eupatorieae tribe within the Asteraceae. Achenes of the Eupatorieae are generally oblong or wedge-shaped, with 5 or 10 longitudinal ridges, and 4-5 angled in edge view (FNA 1993+). The pappus is persistent, made up of long bristles, flat scales, or a combination of the two (FNA 1993+). Ageratum achenes can be distinguished primarily by the pappus composed entirely of flat scales, along with the surface finely papillate tuberculate with sparse hairs.

    Ageratum houstonianum achene

    Additional Botany Information

    AUTRES RENSEIGNEMENTS BOTANIQUES

    Flowers/Inflorescence

    • Flowers blue or violet coloured (Holm et al. 1991)
    • Flower heads are generally flat-topped, with 75-100 flowers per cluster (Holm et al. 1991)
    • The flower head branches, petioles and involucral bracts are densely hairy (Holm et al. 1991)
    • Involucral bracts with entire margins (Holm et al. 1991)

    Vegetative Features

    • Plants 30-80 cm tall (FNA 1993+)
    • Leaves are generally triangular or egg-shaped (Holm et al. 1991; FNA 1993+)
    • Leaf blades length: 2.4-8.6 cm; width: 2.9-6.5 cm (Johnson 1971)
    • Crushed leaves have a strong odour (Holm et al. 1991)

    Similar Species

    ESPÈCES SEMBLABLES

    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.

    Ageratum conyzoides L.

    A. conyzoides, native to South America, is a widespread weed in warm regions of the world, and may be confused with A. houstonianum where ranges overlap (Holm et al. 1991; FNA 1993+). The species are closely related, and reports of invasive potential and crop impacts may refer to the incorrect species of Ageratum (Holm et al. 1991; Lamsal et al. 2022).

    The achenes are a similar size, achene length**: 1.8 – 2.3 mm; width: 0.4 – 0.6 mm (length: 1.25 – 1.75 mm, Johnson 1971) and appearance as A. houstonianum achenes, and would be challenging to distinguish from A. houstonianum.

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

     

    Ageratina spp. Spach

    Achenes are generally a similar size (e.g., A. adenophora (Spreng.) R. M. King & H. Rob. length: 1.5 – 2 mm, Scher et al. 2015). The primary difference is the pappus of Ageratina is a ring of long (length: 2.5 – 4 mm, Scher et al. 2015), straw yellow bristles (FNA 1993+).

     

    Mikania micrantha Kunth

    Achenes are generally similar sized (length: 1.2–2(3) mm long; width: 0.2–0.6 mm, Scher et al. 2015), the ribs are a lighter colour than the achene, surface with scattered or dense yellowish drops of resin, pappus composed of light brown bristles (length: 2 – 3 mm, Scher et al. 2015).

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    Reference(s)

    Référence(s)

    Barua, I.C., Deka, J. and Devi, M. 2013. Invasive weeds and vegetation dynamics in Assam. In: Proceedings of the 24th Asian-Pacific Weed Science Society Conference. 24:166–170.

    Bhatta, R., Joshi, L.R. and Shrestha, B.B. 2020. Distribution and impact of invasive alien plant species in Bardia National Park, western Nepal. Environmental
    Conservation 47: 197–205.

    Bhatta, R., Sharma, P. and Pal, P. 2022. Clinical evaluation of Ageratum houstonianum Mill intoxicated goats. Journal of Agriculture and Forestry University 5: 277-283.

    Bist, M.R. and Shrestha, B.B. 2022. Weed community structure in upland farming system of the middle mountain region in far-western Nepal. Acta Ecologica Sinica. https://doi.org/10.1016/j.chnaes.2022.05.002 (abstract only) Accessed August 18, 2022.

    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/ August 17, 2022.

    Centre for Agriculture and Bioscience International (CABI). 2022. Invasive Species Compendium, CAB International, Wallingford, UK. https://www.cabidigitallibrary.org/journal/cabicompendium Accessed August 18, 2022.

    Flora of China (FOC) 1994+. Ageratum houstonianum Vol. 20-21 Page 879, 883 (English edition). http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200023022 Accessed September 01, 2023.

    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 August 17, 2022.

    Holm, L.G., Plucknett, D.L., Pancho, J.V. and Herberger, J.P. 1991. The World’s Worst Weeds, Distribution and Biology. Krieger Publishing, Florida. 609 pp.

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

    Johnson, M.F. 1971. A Monograph of the Genus Ageratum L. (Compositae-Eupatorieae). Annals of the Missouri Botanical Garden , 58: 6-88.

    Lamsal, A., Devkota, M.P., Shrestha, D.S., Joshi, S. and Shrestha, A. 2019. Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal. PLoS ONE 14(11): e0225430. https://doi.org/10.1371/journal.pone.0225430 Accessed August 17, 2022.

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

    Scher, J. L.,Walters, D.S., and Redford, A.J.. 2015. Federal Noxious Weed Disseminules of the U.S., Edition 2.2. California Department of Food and Agriculture, and USDA APHIS Identification Technology Program. Fort Collins, CO. http://idtools.org/id/fnw Accessed August 18, 2022.

    Stevens, L. 2007. Ageratum houstonianum. In: Anderson, N.O. (ed.) Flower Breeding and Genetics. Springer, The Netherlands. 824 pp.

    The International Union for the Protection of New Varieties of Plants (UPOV). 2011+. GENIE DATABASE. https://www.upov.int/genie/details.xhtml?cropId=168
    Accessed October 24, 2023.

    U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). 2023. Germplasm Resources Information Network (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch Accessed October 24, 2023.

    U.S. Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2022. The PLANTS Database. National Plant Data Team, Greensboro, NC USA. https://plants.usda.gov/home Accessed July 26, 2022.

    Author(s)

    AUTEUR(S)

    Jennifer Neudorf, Angela Salzl, Ruojing Wang

    Canadian Food Inspection Agency

    contactus@idseed.org

    Last updated
    on 2023-03-27

    © 2024 ISMA - International Seed Morphology Association