{{Short description|Genus of plants}} {{For|a virus of the same name|Ageratum yellow vein virus}} {{more citations needed|date=December 2023}} {{Automatic taxobox | image = Ageratum corymbosum (Asteraceae) - Cielitos.jpg | image_caption = ''Ageratum corymbosum'' | display_parents = 2 | taxon = Ageratum | authority = L. 1753 not Mill. 1754 (Plantaginaceae)<ref>{{Cite web|url=https://www.tropicos.org/NameSearch.aspx?name=Ageratum&commonname=|title=Tropicos|website=www.tropicos.org|access-date=2024-01-03|archive-date=2023-05-30|archive-url=https://web.archive.org/web/20230530052928/https://www.tropicos.org/NameSearch.aspx?name=Ageratum&commonname=|url-status=live}}</ref> }}
thumb|right|220px|Bluemink (''Ageratum houstonianum'') '''''Ageratum''''' ({{IPAc-en|ə|ˈ|dʒ|ɛr|ə|t|ə|m}})<ref>''Sunset Western Garden Book,'' 1995:606–607</ref> ('''whiteweed''' in the US) is a genus of 40<ref name="fna">{{eFloras|1|100805|Ageratum |first=Guy L. |last=Nesom |volume=21}}</ref> 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.<ref name="fna" />
They form tussocks or small hills. They grow to a height of {{convert|30|in|cm}}.<ref>{{cite web|url=https://hort.extension.wisc.edu/articles/ageratum|title=Ageratum, ''Ageratum houstonianum''|work=Wisconsin Horticulture – Division of Extension|publisher=University of Wisconsin–Madison|access-date=25 January 2026}}</ref> The opposite leaves are cordate or oval, hairy or tomentose. The margins are slightly toothed or serrate. The leaves form compact clusters.{{citation needed|date=December 2023}}
The fluffy flowers are lavender-blue, pink, lilac, or white, and spread in small compound umbels. They give small, dry fruits.
== Cultivation == Ageratums are grown for their flowers, especially ''A. houstonianum''.
Most common ageratums, "Hawaii" for example, are a short {{convert|6|-|8|in|cm}} when full grown. Tall ageratum are also available in seed catalogues. They are about {{convert|18|in|cm}} in height with blue flowers.<ref>{{cite web|url=https://plants.ces.ncsu.edu/plants/conoclinium-coelestinum|title=''Conoclinium coelestinum''|work=North Carolina Extension Gardener Plant Toolbox|publisher=North Carolina State University|access-date=25 January 2026}}</ref> 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.
== Toxicity == Several species of ''Ageratum'' are toxic, containing pyrrolizidine alkaloids. ''Ageratum houstonianum'' and ''Ageratum conyzoides'' cause liver lesions and are tumorigenic.<ref>Acamovic, T., Stewart, C.S., Pennycott, T.W.,"Poisonous Plants and Related Toxins", 2004</ref><ref>Noa, M., Sanchez, L.M., Durand, R., "Ageratum houstonianum toxicosis in Zebu cattle", Veterinary and human toxicology, 2004, vol. 46, no. 4, pp. 193–195.</ref><ref>Sani, Y., Bahri, S., "Pathological changes in liver due to the toxicity of Ageratum conyzoides", Penyakit Hewan (Indonesia), 1994, v. 26(48) pp. 64–70 [https://cabidigitallibrary.org/doi/full/10.5555/19962200403]</ref><ref>{{cite journal |last1=Fu |first1=P.P. |last2=Yang |first2=Y.-C. |last3=Xia |first3=Q. |last4=Chou |first4=M.W. |last5=Cui |first5=Y.Y. |last6=Lin |first6=G. |title=Pyrrolizidine alkaloids – tumorigenic components in Chinese herbal medicines and dietary supplements |journal=Journal of Food and Drug Analysis |date=2020 |volume=10 |issue=4 |page=8 |doi=10.38212/2224-6614.2743 |url=https://www.researchgate.net/publication/265873732 |doi-access=free }}</ref>
== Weed risk == ''Ageratum conyzoides'' and ''Ageratum houstonianum'' are prone to becoming rampant environmental weeds when grown outside of their natural range.<ref>{{Cite web |url=http://www.hear.org/gcw/species/ageratum_conyzoides/ |title=Global Compendium of Weeds, Ageratum conyzoides (Asteraceae) |access-date=2009-06-21 |archive-date=2020-02-24 |archive-url=https://web.archive.org/web/20200224185757/http://www.hear.org/gcw/species/ageratum_conyzoides/ |url-status=dead }}</ref><ref>{{Cite web |url=http://www.hear.org/gcw/species/ageratum_houstonianum/ |title=Global Compendium of Weeds, Ageratum houstonianum (Asteraceae) |access-date=2009-06-22 |archive-date=2023-02-16 |archive-url=https://web.archive.org/web/20230216143311/http://www.hear.org/gcw/species/ageratum_houstonianum/ |url-status=live }}</ref>
== Species == {{As of|2020|July}}, ''Plants of the World online'' has 40 accepted species:<ref>{{citation |url=http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30004082-2 |title=Kew Science Plants of the World Online |accessdate=15 July 2020 |archive-date=25 November 2022 |archive-url=https://web.archive.org/web/20221125235447/https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30004082-2 |url-status=live }}</ref> {{columns-list|colwidth=22em| * ''Ageratum albidum'' {{Au|Hemsl.}} * ''Ageratum ballotifolium'' {{Au|(Maguire, Steyerm. & Wurdack) R.M.King & H.Rob.}} * ''Ageratum candidum'' {{Au|G.M.Barroso}} * ''Ageratum chiriquense'' {{Au|(B.L.Rob.) R.M.King & H.Rob.}} * ''Ageratum chortianum'' {{Au|Standl. & Steyerm.}} * ''Ageratum conyzoides'' {{Au|L.}} * ''Ageratum corymbosum'' {{Au|(S.F.Blake) L.O.Williams}} * ''Ageratum corymbosum'' {{Au|Zuccagni}} * ''Ageratum echioides'' {{Au|Hemsl.}} * ''Ageratum elassocarpum'' {{Au|S.F.Blake}} * ''Ageratum ellipticum'' {{Au|B.L.Rob.}} * ''Ageratum fastigiatum'' {{Au|(Gardner) R.M.King & H.Rob.}} * ''Ageratum gaumeri'' {{Au|B.L.Rob.}} * ''Ageratum grossedentatum'' {{Au|Rzed.}} * ''Ageratum guatemalense'' {{Au|M.F.Johnson}} * ''Ageratum hondurense'' {{Au|R.M.King & H.Rob.}} * ''Ageratum houstonianum'' {{Au|Mill.}} * ''Ageratum iltisii'' {{Au|R.M.King & H.Rob.}} * ''Ageratum koulianum'' {{Au|Bhellum}} * ''Ageratum littorale'' {{Au|A.Gray}} * ''Ageratum lundellii'' {{Au|R.M.King & H.Rob.}} * ''Ageratum maritimum'' {{Au|Kunth}} * ''Ageratum microcarpum'' {{Au|(Benth.) Hemsl.}} * ''Ageratum microcephalum'' {{Au|Hemsl.}} * ''Ageratum molinae'' {{Au|R.M.King & H.Rob.}} * ''Ageratum munaense'' {{Au|R.M.King & H.Rob.}} * ''Ageratum myriadenium'' {{Au|(Baker) R.M.King & H.Rob.}} * ''Ageratum oerstedii'' {{Au|B.L.Rob}} * ''Ageratum paleaceum'' {{Au|(J.Gay ex DC.) Hemsl.}} * ''Ageratum peckii'' {{Au|B.L.Rob}} * ''Ageratum petiolatum'' {{Au|(Hook. & Arn.) Hemsl.}} * ''Ageratum platylepis'' {{Au|(B.L.Rob.) R.M.King & H.Rob.}} * ''Ageratum platypodum'' {{Au|B.L.Rob}} * ''Ageratum riparium'' {{Au|B.L.Rob.}} * ''Ageratum rugosum'' {{Au|J.M.Coult.}} * ''Ageratum salvanaturae'' {{Au|B.Smalla & N.Kilian}} * ''Ageratum scorpioideum'' {{Au|Baker}} * ''Ageratum solisii'' {{Au|B.L.Turner}} * ''Ageratum standleyi'' {{Au|B.L.Rob}} * ''Ageratum tehuacanum'' {{Au|R.M.King & H.Rob.}} * ''Ageratum tomentosum'' {{Au|(Benth.) Hemsl.}} }}
Selected synonyms include: * ''Ageratum altissimum'' {{Au|L.}} – synonym of ''Ageratina altissima'' {{Au|(L.) R.M.King & H.Rob.}} * ''Ageratum anisochroma'' {{Au|(Klatt) R.M.King & H.Rob.}} – synonym of ''Ageratina anisochroma'' {{Au|(Klatt) R.M.King & H.Rob.}} * ''Ageratum isocarphoides'' {{Au|(DC.) Hemsl.}} – synonym of ''Ageratum echioides'' {{Au|Hemsl.}} * ''Ageratum lavenia'' {{Au|(L.) Kuntze}} – synonym of ''Adenostemma lavenia'' {{Au|(L.) Kuntze}} * ''Ageratum lucidum'' {{Au|B.L.Rob.}} – synonym of ''Ageratum corymbosum'' {{Au|Zuccagni}} * ''Ageratum meridanum'' {{Au|V.M.Badillo}} – synonym of ''Ageratum microcarpum'' {{Au|(Benth.) Hemsl.}} * ''Ageratum nelsonii'' {{Au|(B.L.Rob.) M.F.Johnson}} – synonym of ''Ageratum elassocarpum'' {{Au|S.F.Blake}} * ''Ageratum oliveri'' {{Au|R.M.King & H.Rob.}} – synonym of ''Ageratum oerstedii'' {{Au|B.L.Rob.}} * ''Ageratum panamense'' {{Au|B.L.Rob.}} – synonym of ''Ageratum riparium'' {{Au|B.L.Rob.}} * ''Ageratum pohlii'' {{Au|(Baker) H.Rob.}} – synonym of ''Teixeiranthus pohlii'' {{Au|(Baker) R.M.King & H.Rob.}} * ''Ageratum radicans'' {{Au|B.L.Rob.}} – synonym of ''Ageratum peckii'' {{Au|B.L.Rob.}} * ''Ageratum salicifolium'' {{Au|Hemsl.}} – synonym of ''Ageratum corymbosum'' {{Au|Zuccagni}} * ''Ageratum stachyofolium'' {{Au|B.L.Rob.}} – synonym of ''Paneroa stachyofolia'' {{Au|(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''.<ref>{{cite journal | doi = 10.3417/2007173 | title = Paneroa, A New Genus of Eupatorieae (Asteraceae) from Mexico | year = 2008 | author = Schilling, Edward E. | journal = Novon: A Journal for Botanical Nomenclature | volume = 18 | issue = 4 | pages = 520–523 | s2cid = 85729667 | url = https://www.biodiversitylibrary.org/part/58019 | access-date = 2023-01-21 | archive-date = 2023-11-08 | archive-url = https://web.archive.org/web/20231108142313/https://www.biodiversitylibrary.org/part/58019 | url-status = live }}</ref>
== References == {{Reflist|2}}
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Category:Ageratum Category:Asteraceae genera Category:Botanical taxa named by Carl Linnaeus