Bidens cernua

{{short description|Species of flowering plant in the daisy family Asteraceae}} {{Speciesbox |image = Bidens cernua.jpeg |status = {{TNCStatus}} |status_system = TNC |genus = Bidens |species = cernua |authority = L. |synonyms = * ''Bidens ciliolata'' Greene * ''Bidens cusickii'' Greene * ''Bidens dentata'' (Nutt.) Wiegand * ''Bidens elliptica'' (Wiegand) Gleason * ''Bidens filamentosa'' Rydb. * ''Bidens gracilenta'' Greene * ''Bidens graveolens'' Komarov 1916 not Mart. 1824 * ''Bidens kelloggii'' Greene * ''Bidens leptomeria'' Greene * ''Bidens leptopoda'' Greene * ''Bidens lonchophylla'' Greene * ''Bidens macounii'' Greene * ''Bidens marginata'' Greene 1901 not Perr ex DC. 1836 * ''Bidens minima'' Huds. * ''Bidens prionophylla'' Greene * ''Bidens quadriaristata'' var. ''dentata'' Nutt. * ''Bidens tripartita'' var. ''minima'' Huds. * ''Bidens venosa'' Gardner * ''Buphthalmum nutans'' Vitman * ''Coreopsis bidens'' L. * ''Coreopsis quadricornis'' Krock. * ''Coreopsis ridens'' Gunnerus |synonyms_ref = <ref>{{cite web|url=http://www.theplantlist.org/tpl/record/gcc-103570|title=The Plant List: A Working List of All Plant Species}}</ref><ref>{{cite web|url=http://www.ipni.org/ipni/advPlantNameSearch.do?find_family=&find_genus=coreopsis&find_species=ridens&find_infrafamily=&find_infragenus=&find_infraspecies=&find_authorAbbrev=&find_includePublicationAuthors=on&find_includePublicationAuthors=off&find_includeBasionymAuthors=on&find_includeBasionymAuthors=off&find_publicationTitle=&find_isAPNIRecord=on&find_isAPNIRecord=false&find_isGCIRecord=on&find_isGCIRecord=false&find_isIKRecord=on&find_isIKRecord=false&find_rankToReturn=all&output_format=normal&find_sortByFamily=on&find_sortByFamily=off&query_type=by_query&back_page=plantsearch|title=IPNI entry for ''Coreopsis ridens''}}</ref><ref>{{cite web|url=http://www.ipni.org/ipni/advPlantNameSearch.do?find_family=&find_genus=bidens&find_species=venosa&find_infrafamily=&find_infragenus=&find_infraspecies=&find_authorAbbrev=&find_includePublicationAuthors=on&find_includePublicationAuthors=off&find_includeBasionymAuthors=on&find_includeBasionymAuthors=off&find_publicationTitle=&find_isAPNIRecord=on&find_isAPNIRecord=false&find_isGCIRecord=on&find_isGCIRecord=false&find_isIKRecord=on&find_isIKRecord=false&find_rankToReturn=all&output_format=normal&find_sortByFamily=on&find_sortByFamily=off&query_type=by_query&back_page=plantsearch|title=IPNI entry for ''Bidens venosa''}}</ref> }}

'''''Bidens cernua''''' is a species of flowering plant in the aster family, Asteraceae.<ref name="x" /><ref name=":0" /><ref name=":1" /><ref name=":2" /> It is commonly called '''nodding beggarticks'''<ref>{{cite book |author=Voss, E.G. |title=Michigan Flora: A guide to the identification and occurrence of the native and naturalized seed-plants of the state. Part III: Dicots (Pyrolaceae–Compositae) |publisher=Cranbrook Institute of Science and University of Michigan Herbarium |year=1996 |volume=Bulletin 61 |location=Ann Arbor, Michigan, U.S.A.}}</ref> or '''nodding bur-marigold.''' ''Bidens cernua'' is distributed throughout much of Eurasia and North America.<ref name="x">[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200023533 Flora of North America, ''Bidens cernua'' Linnaeus, Sp. Pl. 2: 832. 1753. ]</ref><ref name=":0">[http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200023533 Flora of China, <big>柳叶鬼针草</big> liu ye gui zhen cao, ''Bidens cernua'' Linnaeus, Sp. Pl. 2: 832. 1753]</ref><ref name=":1">[http://bonap.net/MapGallery/County/Bidens%20cernua.png Biota of North America Program 2014 county distribution map]</ref><ref name=":2">[http://luirig.altervista.org/flora/taxa/index1.php?scientific-name=bidens+cernua Altervista Flora Italiana, Forbicina intera, ''Bidens cernua'' L.] includes photos and European distribution map</ref><ref name="BSBI07">{{BSBI 2007|accessdate=2014-10-17}}</ref> thumb thumb

== Description == ''Bidens cernua'' is an annual species growing roughly 1m tall, with a fibrous root. Stems are rigid and often either simple or beached. Stem leaves are simple, unstalked, and opposite with saw-toothed to almost smooth margins.<ref name=":3">{{Cite book |last=Pojar |first=Jim |title=Plants of the Pacific northwest coast: Washington, Oregon, British Columbia & Alaska |last2=MacKinnon |first2=Andrew |date=2004 |publisher=Lone Pine |isbn=978-1-55105-530-5 |edition=Revised |location=Vancouver}}</ref>

It has yellow flowers with 6-8 ray narrowly lance shaped petals around a central disk. The hemispheric heads are solitary at the ends of branches and nod with age.<ref name=":3" />

The achenes are narrowly wedge-shaped and 4-sided, flattened and ribbed. The pappus has 3-4 barbed bristles.<ref name=":3" />

== Distribution and abundance == ''Bidens cernua'' is distributed throughout much of Eurasia and North America.<ref name="x" /><ref name=":0" /><ref name=":2" /><ref name=":1" />

==References== {{Reflist}}

cernua Category:Flora of Asia Category:Flora of Northern America Category:Flora of Europe Category:Plants described in 1753 Category:Botanical taxa named by Carl Linnaeus