# Acaena

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{{Short description|Genus of flowering plants}}
{{Automatic taxobox
|image = Acaena novae-zelandiae1.jpg
|image_caption = ''[Acaena novae-zelandiae](/source/Acaena_novae-zelandiae)'' foliage and various fruiting stages
|display_parents = 3
|taxon = Acaena
|authority = [Mutis](/source/Jos%C3%A9_Celestino_Bruno_Mutis) ex [L.](/source/Carl_Linnaeus)<ref name=GRIN>{{GRIN genus | name = ''Acaena'' | id = 27 | accessdate = 30 March 2020}}</ref>
|subdivision_ranks = Species
|subdivision = See text
|synonyms =
*''Ancistrum'' {{Au|J.R.Forst. & G.Forst.}}
|synonyms_ref = <ref name=GRIN/>
}}

'''''Acaena''''' is a [genus](/source/genus) of about 60 species of mainly [evergreen](/source/evergreen), [creeping](/source/prostrate_shrub) [herbaceous](/source/herbaceous_plant) [perennial plants](/source/perennial_plants) and [subshrub](/source/subshrub)s in the family [Rosaceae](/source/Rosaceae), [native](/source/native_plant) mainly to the Southern Hemisphere, notably New Zealand, Australia and South America, but with a few species extending into the Northern Hemisphere, north to Hawaii (''[A. exigua](/source/Acaena_exigua)'') and California (''[A. pinnatifida](/source/Acaena_pinnatifida)'').<ref>{{cite book|title=RHS A-Z encyclopedia of garden plants|year=2008|publisher=Dorling Kindersley|location=United Kingdom|isbn=1405332964|page=1136}}</ref>

The [leaves](/source/leaf) are alternate, {{convert|4|-|15|cm|in}} long, and pinnate or nearly so, with 7–21 [leaflets](/source/leaflet_(botany)). The [flower](/source/flower)s are produced in a tight globose [inflorescence] {{convert|1|-|2|cm|in}} in diameter, with no petals. The [fruit](/source/fruit) is also a dense ball of many [seed](/source/seed)s; in many (but not all) species the seeds bear a barbed arrowhead point, the seedhead forming a [burr](/source/burr_(fruit)) which attaches itself to animal fur or feathers for dispersal.

Several ''Acaena'' species in New Zealand are known by the common name '''bidibid'''. The word is written variously ''bidi-bidi'', ''biddy-biddy'', ''biddi-biddi'', ''biddi-bid'' and a number of other variations. These names are the English rendition of the original Māori name of ''piripiri''.<ref>Orsman, H. W. (1999). ''The Dictionary of New Zealand English''. Auckland: Oxford University Press.</ref> The plant is also called the New Zealand burr.  The species ''[Acaena microphylla](/source/Acaena_microphylla)'' has gained the [Royal Horticultural Society](/source/Royal_Horticultural_Society)'s [Award of Garden Merit](/source/Award_of_Garden_Merit).<ref>[http://apps.rhs.org.uk/plantselector/plant?plantid=13 RHS Plant Selector Acaena microphylla AGM / RHS Gardening<!-- Bot generated title -->]{{Dead link|date=June 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

== Etymology ==
The generic name ''Acaena'' is derived from the Greek "akaina" (thorn), referring to the spiny [hypanthium](/source/hypanthium).<ref>{{cite web|website= E-Flora (Flora of North America)|title= Rosaceae 26. Acaena|author= Bryony Macmillan|url= http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=100063|accessdate= 2015-12-03}}</ref>

==Species==
{{As of|2020}}, [Plants of the World Online](/source/Plants_of_the_World_Online) accepted the following species:<ref name=POWO>{{cite web | title = ''Acaena'' | work = [Plants of the World Online](/source/Plants_of_the_World_Online) | publisher = [Royal Botanic Gardens, Kew](/source/Royal_Botanic_Gardens%2C_Kew) | url = https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30001386-2 | accessdate = 30 March 2020}}</ref>
{{Div col}}
*''[Acaena agnipila](/source/Acaena_agnipila)'' {{Au|Gand.}}
*''[Acaena alpina](/source/Acaena_alpina)'' {{Au|Poepp. ex Walp.}}
*''[Acaena anserinifolia](/source/Acaena_anserinifolia)'' {{Au|(J.R.Forst. & G.Forst.) J.B.Armstr.}}
*''[Acaena antarctica](/source/Acaena_antarctica)'' {{Au|Hook.f.}}
*''[Acaena argentea](/source/Acaena_argentea)'' {{Au|Ruiz & Pav.}}
*''[Acaena boliviana](/source/Acaena_boliviana)'' {{Au|Gand.}}
*''[Acaena buchananii](/source/Acaena_buchananii)'' {{Au|Hook.f.}}
*''[Acaena caesiiglauca](/source/Acaena_caesiiglauca)'' {{Au|(Bitter) Bergmans}} – glaucous pirri-pirri-bur
*''[Acaena caespitosa](/source/Acaena_caespitosa)'' {{Au|Gillies ex Hook. & Arn.}}
*''[Acaena confertissima](/source/Acaena_confertissima)'' {{Au|Bitter}}
*''[Acaena cylindristachya](/source/Acaena_cylindristachya)'' {{Au|Ruiz & Pav.}}
*''[Acaena dumicola](/source/Acaena_dumicola)'' {{Au|B.H.Macmill.}} ([South Island](/source/South_Island) of New Zealand)
*''[Acaena echinata](/source/Acaena_echinata)'' {{Au|Nees}} – sheep's burr
*''[Acaena elongata](/source/Acaena_elongata)'' {{Au|L.}}
*''[Acaena emittens](/source/Acaena_emittens)'' {{Au|B.H.Macmill.}} ([North Island](/source/North_Island) of New Zealand)
*''[Acaena eupatoria](/source/Acaena_eupatoria)'' {{Au|Cham. & Schltdl.}}
*''[Acaena exigua](/source/Acaena_exigua)'' {{Au|A.Gray}} – ''liliwai'' ([Hawai{{okina}}i](/source/Hawaii))
*''[Acaena fissistipula](/source/Acaena_fissistipula)'' {{Au|Bitter}}
*''[Acaena fuscescens](/source/Acaena_fuscescens)'' {{Au|Bitter}}
*''[Acaena glabra](/source/Acaena_glabra)'' {{Au|Buchanan}}
*''[Acaena hirsutula](/source/Acaena_hirsutula)'' {{Au|Bitter}}
*''[Acaena inermis](/source/Acaena_inermis)'' {{Au|Hook.f.}}
*''[Acaena integerrima](/source/Acaena_integerrima)'' {{Au|Gillies ex Hook. & Arn.}}
*''[Acaena juvenca](/source/Acaena_juvenca)'' {{Au|B.H.Macmill.}} (New Zealand)
*''[Acaena latebrosa](/source/Acaena_latebrosa)'' {{Au|W.T.Aiton}}
*''[Acaena leptacantha](/source/Acaena_leptacantha)'' {{Au|Phil.}}
*''[Acaena longiscapa](/source/Acaena_longiscapa)'' {{Au|Bitter}}
*''[Acaena lucida](/source/Acaena_lucida)'' {{Au|(Aiton) Vahl}}
*''[Acaena macrocephala](/source/Acaena_macrocephala)'' {{Au|Poepp.}}
*''[Acaena magellanica](/source/Acaena_magellanica)'' {{Au|(Lam.) Vahl}} – greater burnet
*''[Acaena masafuerana](/source/Acaena_masafuerana)'' {{Au|Bitter}}
*''[Acaena microphylla](/source/Acaena_microphylla)'' {{Au|Hook.f.}} – New Zealand-bur
*''[Acaena minor](/source/Acaena_minor)'' {{Au|(Hook.f.) Allan}}
*''[Acaena montana](/source/Acaena_montana)'' {{Au|Hook.f.}}
*''[Acaena myriophylla](/source/Acaena_myriophylla)'' {{Au|Lindl.}}
*''[Acaena novae-zelandiae](/source/Acaena_novae-zelandiae)'' {{Au|Kirk}} – red bidibid (New Zealand)
*''[Acaena ovalifolia](/source/Acaena_ovalifolia)'' {{Au|(Vahl) Ruiz & Pav.}}
*''[Acaena ovina](/source/Acaena_ovina)'' {{Au|A.Cunn.}}
*''[Acaena pallida](/source/Acaena_pallida)'' {{Au|(Kirk) Allan}} – sand bidibid
*''[Acaena patagonica](/source/Acaena_patagonica)'' {{Au|A.E.Martic.}}
*''[Acaena pinnatifida](/source/Acaena_pinnatifida)'' {{Au|Ruiz & Pav.}} – Argentinian biddy-biddy
*''[Acaena platyacantha](/source/Acaena_platyacantha)'' {{Au|Speg.}}
*''[Acaena poeppigiana](/source/Acaena_poeppigiana)'' {{Au|Gay}}
*''[Acaena profundeincisa](/source/Acaena_profundeincisa)'' {{Au|(Bitter) B.H.Macmill.}}
*''[Acaena pumila](/source/Acaena_pumila)'' {{Au|Vahl}}
*''[Acaena rorida](/source/Acaena_rorida)'' {{Au|B.H.Macmill.}} (North Island)
*''[Acaena saccaticupula](/source/Acaena_saccaticupula)'' {{Au|Bitter}}
*''[Acaena sarmentosa](/source/Acaena_sarmentosa)'' {{Au|(Thouars) Carmich.}}
*''[Acaena sericea](/source/Acaena_sericea)'' {{Au|J.Jacq.}}
*''[Acaena splendens](/source/Acaena_splendens)'' {{Au|Hook. & Arn.}}
*''[Acaena stangii](/source/Acaena_stangii)'' {{Au|Christoph.}}
*''[Acaena stricta](/source/Acaena_stricta)'' {{Au|Griseb.}}
*''[Acaena subincisa](/source/Acaena_subincisa)'' {{Au|Wedd.}}
*''[Acaena tenera](/source/Acaena_tenera)'' {{Au|Albov}} – lesser burnet
*''[Acaena tesca](/source/Acaena_tesca)'' {{Au|B.H.Macmill.}} (South Island)
*''[Acaena torilicarpa](/source/Acaena_torilicarpa)'' {{Au|Bitter}}
*''[Acaena trifida](/source/Acaena_trifida)'' {{Au|Ruiz & Pav.}}
{{Div col end}}

==Invasive species==
Some species have been introduced accidentally to other areas, attached to [sheep](/source/sheep)'s [wool](/source/wool), and have become [invasive species](/source/invasive_species). ''[Acaena novae-zelandiae](/source/Acaena_novae-zelandiae)'', one of the bidibids from New Zealand, is the most commonly encountered species in the [United Kingdom](/source/United_Kingdom), where it is often abundant on coastal sand dunes, crowding out native vegetation and creating an often painful nuisance with the barbed burrs. In California, ''[A. pallida](/source/Acaena_pallida)'', ''A. novae-zelandiae'' and ''[A. anserinifolia](/source/Acaena_anserinifolia)'' are considered serious weeds.<ref>[https://archive.today/20130616101927/http://www.cdfa.ca.gov/plant/ipc/weedinfo/winfo_list-pestrating.htm "Weeds Sorted by Pest Rating"], CFDA.ca.gov</ref>

==References==
{{Reflist}}

==External links==
{{Commons category}}
*[http://ucjeps.berkeley.edu/cgi-bin/get_JM_treatment.pl?6677,6678 Jepson Manual Treatment]
*[https://plants.usda.gov/java/profile?symbol=ACAEN USDA Plants Profile]
*[https://web.archive.org/web/20080408043341/http://www.landcareresearch.co.nz/ Landcare Research New Zealand]

{{Taxonbar|from=Q1327017}}

Category:Acaena
Category:Pantropical flora
Category:Rosaceae genera

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Adapted from the Wikipedia article [Acaena](https://en.wikipedia.org/wiki/Acaena) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Acaena?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.