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Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Asterids
Cladus: Campanulids
Ordo: Asterales

Familia: Asteraceae
Subfamilia: Asteroideae
Tribus: Eupatorieae
Subtribus: Ageratinae
Genus: Ageratum
Species: A. albidum – A. ballotifolium – A. candidum – A. chiriquense – A. chortianum – A. conyzoides – A. cordatum – A. corymbosum – A. echioides – A. ellipticum – A. fastigiatum – A. gaumeri – A. guatemalense – A. hondurense – A. houstonianum – A. iltisii – A. koulianum – A. littorale – A. lundellii – A. maritimum – A. microcarpum – A. microcephalum – A. molinae – A. munaense – A. myriadenium – A. oerstedii – A. oliveri – A. paleaceum – A. peckii – A. petiolatum – A. platylepis – A. platypodum – A. radicans – A. riparium – A. salvanaturae – A. solisii – A. standleyi – A. tehuacanum – A. tomentosum

Ageratum L., Sp. Pl. 2: 839. (1753)

Type species: Ageratum conyzoides L., Sp. Pl. 2: 839. (1753)


Carelia Fabr., Enum. 85. (1759)
Caelestina Cass., Bull. Sci. Soc. Philom. Paris 1817: 10. (1817)
Coelestina Cass., Bull. Sci. Soc. Philom. Paris 1817: 10. (1817)
Isocarpha Less., Linnaea 5: 141. (1830)
Ageratum subg. Caelestina (Cass.) Baker, Fl. Bras. 6(2): 197. (1876)
Ageratum sect. Caelestina (Cass.) A. Gray ex B.L. Rob., Proc. Amer. Acad. Arts 49(8): 468. (1914)
Blakeanthus R.M.King & H.Rob., Phytologia 24(2): 118–119. (1972)


Linnaeus, C. 1753. Species Plantarum. Tomus II: 839. Reference page.
Hassler, M. 2018. Ageratum. World Plants: Synonymic Checklists of the Vascular Plants of the World In: Roskovh, Y., Abucay, L., Orrell, T., Nicolson, D., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., Nieukerken, E. van, Zarucchi, J. & Penev, L., eds. 2018. Species 2000 & ITIS Catalogue of Life. Published online. Accessed: 2018 January 1. Reference page.
International Plant Names Index. 2018. Ageratum. Published online. Accessed: January 1 2018.
The Plant List 2013. Ageratum in The Plant List Version 1.1. Published online. Accessed: 2018 January 1. 2018. Ageratum. Missouri Botanical Garden. Published online. Accessed: 1 January 2018.

Vernacular names
dansk: Blåkvast
English: Whiteweed
suomi: Sinitähtöset
հայերեն: Անծերի
lietuvių: Žydrūnis
polski: Żeniszek
русский: Агератум
Türkçe: Vapurdumanı
українська: Агератум

Ageratum (/əˈdʒɛrətəm/)[2] (whiteweed in the USA) is a genus of 40[3] to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native to the United States.[3]

They form tussocks or small hills. They grow to a height of 30 in. The opposite leaves are cordate or oval, hairy or tomentose. The margins are slightly toothed or serrate. The leaves form compact clusters.

The fluffy flowers are lavender-blue, pink, lilac, or white; and spread in small compound umbels. They give small, dry fruits.


Ageratums are grown for their flowers, especially A. houstonianum.

Most common ageratums, "Hawaii" for example, are a short 6-8 inches when full grown. Tall ageratum are also available in seed catalogues. They are about 18 inches in height with blue flowers. There is also a medium height snowcapped variety, white top on blue flowers. The blues are most popular and common, but colors also include violet, pink and white. Their size and color makes ageratums good candidates for rock gardens, bedding, and containers. They grow well in sun or partial shade, from early summer to first frost. They are quite easy to grow, producing a profusion of fluffy flowers all season long.

Several species of Ageratum are toxic, containing pyrrolizidine alkaloids. Ageratum houstonianum and Ageratum conyzoides cause liver lesions and are tumorigenic.[4][5][6][7]
Weed risk

Ageratum conyzoides and Ageratum houstonianum are prone to becoming rampant environmental weeds when grown outside of their natural range.[8][9]

As of July 2020, Plants of the World online has 40 accepted species:[10]

Ageratum albidum Hemsl.
Ageratum ballotifolium (Maguire, Steyerm. & Wurdack) R.M.King & H.Rob.
Ageratum candidum G.M.Barroso
Ageratum chiriquense (B.L.Rob.) R.M.King & H.Rob.
Ageratum chortianum Standl. & Steyerm.
Ageratum conyzoides L.
Ageratum corymbosum (S.F.Blake) L.O.Williams
Ageratum corymbosum Zuccagni
Ageratum echioides Hemsl.
Ageratum elassocarpum S.F.Blake
Ageratum ellipticum B.L.Rob.
Ageratum fastigiatum (Gardner) R.M.King & H.Rob.
Ageratum gaumeri B.L.Rob.
Ageratum grossedentatum Rzed.
Ageratum guatemalense M.F.Johnson
Ageratum hondurense R.M.King & H.Rob.
Ageratum houstonianum Mill.
Ageratum iltisii R.M.King & H.Rob.
Ageratum koulianum Bhellum
Ageratum littorale A.Gray
Ageratum lundellii R.M.King & H.Rob.
Ageratum maritimum Kunth
Ageratum microcarpum (Benth.) Hemsl.
Ageratum microcephalum Hemsl.
Ageratum molinae R.M.King & H.Rob.
Ageratum munaense R.M.King & H.Rob.
Ageratum myriadenium (Baker) R.M.King & H.Rob.
Ageratum oerstedii B.L.Rob
Ageratum paleaceum (J.Gay ex DC.) Hemsl.
Ageratum peckii B.L.Rob
Ageratum petiolatum (Hook. & Arn.) Hemsl.
Ageratum platylepis (B.L.Rob.) R.M.King & H.Rob.
Ageratum platypodum B.L.Rob
Ageratum riparium B.L.Rob.
Ageratum rugosum J.M.Coult.
Ageratum salvanaturae B.Smalla & N.Kilian
Ageratum scorpioideum Baker
Ageratum solisii B.L.Turner
Ageratum standleyi B.L.Rob
Ageratum tehuacanum R.M.King & H.Rob.
Ageratum tomentosum (Benth.) Hemsl.

Selected synonyms include:

Ageratum altissimum L. — synonym of Ageratina altissima (L.) R.M.King & H.Rob.
Ageratum anisochroma (Klatt) R.M.King & H.Rob. — synonym of Ageratina anisochroma (Klatt) R.M.King & H.Rob.
Ageratum isocarphoides (DC.) Hemsl. — synonym of Ageratum echioides Hemsl.
Ageratum lavenia (L.) Kuntze — synonym of Adenostemma lavenia (L.) Kuntze
Ageratum lucidum B.L.Rob. — synonym of Ageratum corymbosum Zuccagni
Ageratum meridanum V.M.Badillo — synonym of Ageratum microcarpum (Benth.) Hemsl.
Ageratum nelsonii (B.L.Rob.) M.F.Johnson — synonym of Ageratum elassocarpum S.F.Blake
Ageratum oliveri R.M.King & H.Rob. — synonym of Ageratum oerstedii B.L.Rob.
Ageratum panamense B.L.Rob. — synonym of Ageratum riparium B.L.Rob.
Ageratum pohlii (Baker) H.Rob. — synonym of Teixeiranthus pohlii (Baker) R.M.King & H.Rob.
Ageratum radicans B.L.Rob. — synonym of Ageratum peckii B.L.Rob.
Ageratum salicifolium Hemsl. — synonym of Ageratum corymbosum Zuccagni
Ageratum stachyofolium B.L.Rob. — synonym of Paneroa stachyofolia (B.L.Rob.) E.E.Schill.

Segregate genera

The genus Paneroa consists of one species, Paneroa stachyofolia, native to Oaxaca, which was first described in Ageratum but which seems to be more closely related to Conoclinium and Fleischmannia.[11]

Tropicos, search for Ageratum
Sunset Western Garden Book, 1995:606–607
Nesom, Guy L. (2006). "Ageratum". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 21. New York and Oxford – via, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Acamovic, T., Stewart, C.S., Pennycott, T.W.,"Poisonous Plants and Related Toxins", 2004
Noa, M., Sanchez, L.M., Durand, R., "Ageratum houstonianum toxicosis in Zebu cattle", Veterinary and human toxicology, 2004, vol.46, no4, pp.193-195.
Sani, Y., Bahri, S., "Pathological changes in liver due to the toxicity of Ageratum conyzoides", Penyakit Hewan (Indonesia), 1994, v. 26(48) p. 64-70 [1]
Fu, P.P., Yang, Y.C., Xia, Q., Chou, M.C., Cui, Y.Y., Lin G., "Pyrrolizidine alkaloids-tumorigenic components in Chinese herbal medicines and dietary supplements", Journal of Food and Drug Analysis, Vol. 10, No. 4, 2002, pp. 198-211 [2][permanent dead link]
Global Compendium of Weeds, Ageratum conyzoides (Asteraceae)
Global Compendium of Weeds, Ageratum houstonianum (Asteraceae)
Kew Science Plants of the World Online, retrieved 15 July 2020
Schilling, Edward E. (2008). "Paneroa, A New Genus of Eupatorieae (Asteraceae) from Mexico". Novon: A Journal for Botanical Nomenclature. 18 (4): 520–523. doi:10.3417/2007173. S2CID 85729667.

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