Editing Centaurea

{{Short description|Genus of flowering plants}}
{{Redirect|Basket flower|the unrelated Australian plant |Adenanthos obovatus}}
{{Automatic taxobox
|image = Centaurea pullata b.JPG
|image_caption = ''[[Centaurea pullata]]''
|display_parents = 3
|taxon = Centaurea
|authority = [[Carl Linnaeus|L.]]
|type_species = ''[[Centaurea paniculata]]''
|type_species_authority = L.
|diversity_link = #Species
|diversity = Over 700 species
|synonyms =  {{hidden begin|title = List}} 
* ''Acosta'' <small>DC.</small>
* × ''Acostitrapa'' <small>Rauschert</small>
* ''Acrocentron'' <small>Cass.</small>
* ''Acrolophus'' <small>Cass.</small>
* ''Alophium'' <small>Cass.</small>
* ''Ammocyanus'' <small>(Boiss.) Dostál</small>
* ''Antaurea'' <small>Neck.</small>
* ''Behen'' <small>Hill</small>
* ''Benedicta'' <small>Bernh.</small>
* ''Calcitrapa'' <small>Heist. ex Fabr.</small>
* ''Calcitrapoides'' <small>Fabr.</small>
* ''Carbeni'' <small>Adans.</small>
* ''Carbenia'' <small>Adans.</small>
* ''Cardosanctus'' <small>Bubani</small>
* ''Cestrinus'' <small>Cass.</small>
* ''Chartolepis'' <small>Cass.</small>
* ''Cheirolepis'' <small>Boiss.</small>
* ''Chrysopappus'' <small>Takht.</small>
* ''Cistrum'' <small>Hill</small>
* ''Cnicus'' <small>L.</small>
* × ''Colycea'' <small>Fern.Casas & Susanna</small>
* × ''Colymbacosta'' <small>Rauschert</small>
* ''Colymbada'' <small>Hill</small>
* ''Crepula'' <small>Hill</small>
* ''Cyanus'' <small>Mill.</small>
* ''Cynaroides'' <small>(Boiss. ex Walp.) Dostál</small>
* ''Eremopappus'' <small>Takht.</small>
* ''Erinacella'' <small>(Rech.f.) Dostál</small>
* ''Eriopha'' <small>Hill</small>
* ''Grossheimia'' <small>Sosn. & Takht.</small>
* ''Heraclea'' <small>Hill</small>
* ''Hierapicra'' <small>Kuntze</small>
* ''Hippophaestum'' <small>Gray</small>
* ''Hookia'' <small>Neck.</small>
* ''Hyalea'' <small>Jaub. & Spach</small>
* ''Hymenocentron'' <small>Cass.</small>
* ''Jacea'' <small>Mill.</small>
* × ''Jaceacosta'' <small>Rauschert</small>
* × ''Jaceitrapa'' <small>Rauschert</small>
* ''Lepteranthus'' <small>Neck. ex Fourr.</small>
* ''Leucacantha'' <small>Nieuwl. & Lunell</small>
* ''Leucantha'' <small>Gray</small>
* ''Lopholoma'' <small>Cass.</small>
* ''Melanoloma'' <small>Cass.</small>
* ''Menomphalus'' <small>Pomel</small>
* ''Mesocentron'' <small>Cass.</small>
* ''Microlophus'' <small>Cass.</small>
* ''Paraphysis'' <small>(DC.) Dostál</small>
* ''Pectinastrum'' <small>Cass.</small>
* ''Petrodavisia'' <small>Holub</small>
* ''Phaeopappus'' <small>(DC.) Boiss.</small>
* ''Phalolepis'' <small>Cass.</small>
* ''Philostizus'' <small>Cass.</small>
* ''Phrygia'' <small>(Pers.) Bosc</small>
* ''Piptoceras'' <small>Cass.</small>
* ''Platylophus'' <small>Cass.</small>
* ''Plumosipappus'' <small>Czerep.</small>
* ''Podia'' <small>Neck.</small>
* ''Polyacantha'' <small>Gray</small>
* ''Psora'' <small>Hill</small>
* ''Pterolophus'' <small>Cass.</small>
* ''Pycnocomus'' <small>Hill</small>
* ''Rhacoma'' <small>Adans.</small>
* ''Sagmen'' <small>Hill.</small>
* ''Seridia'' <small>Juss.</small>
* ''Setachna'' <small>Dulac</small>
* ''Solstitiaria'' <small>Hill</small>
* ''Sphaerocephala'' <small>Hill</small>
* ''Spilacron'' <small>Cass.</small>
* ''Staebe'' <small>Hill</small>
* ''Stenolophus'' <small>Cass.</small>
* ''Stephanochilus'' <small>Coss. ex Maire</small>
* ''Tetramorphaea'' <small>DC.</small>
* ''Tomanthea'' <small>DC.</small>
* ''Triplocentron'' <small>Cass.</small>
* ''Veltis'' <small>Adans.</small>
* ''Verutina'' <small>Cass.</small>
* ''Wagenitzia'' <small>Dostál</small>
{{hidden end}}
}}

'''''Centaurea''''' ({{IPAc-en|ˌ|s|ɛ|n|t|ɔː|ˈ|r|iː|ə}})<ref>''Sunset Western Garden Book,'' 1995:606–607</ref> is a [[genus]] of over 700 species of [[herb]]aceous [[thistle]]-like flowering plants in the family [[Asteraceae]]. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich.

==Common names==
Common names for this genus are '''centaury''', '''centory''', '''starthistles''', '''knapweeds''', '''centaureas''' and the more ambiguous "'''bluets'''"; a vernacular name used for these plants in parts of England is "'''loggerheads'''" ([[common knapweed]]). The ''Plectocephalus'' group &ndash; possibly a distinct genus &ndash; is known as '''basketflowers'''. '''"Cornflower"''' is used for a few species, but that term more often specifically means either ''[[Centaurea cyanus|C. cyanus]]'' (the annual cornflower) or ''[[Centaurea montana]]'' (the perennial cornflower). The common name "'''centaury'''" is sometimes used, although this also refers to the unrelated plant genus ''[[Centaurium]]''.<ref name=kko2006>Keil (2006), Keil & Ochsmann (2006).</ref>

The name is said to be in reference to [[Chiron]], the centaur of [[Greek mythology]] who discovered medicinal uses of a plant eventually called "centaury".<ref>{{Cite book |last=Blackwell |first=Laird R. |url=https://www.worldcat.org/oclc/61461560 |title=Great Basin Wildflowers: A Guide to Common Wildflowers of the High Deserts of Nevada, Utah, and Oregon (A Falcon Guide) |publisher=[[Morris Book Publishing, LLC]] |year=2006 |isbn=0-7627-3805-7 |edition=1st |location=Guilford, Conn. |pages=57 |oclc=61461560}}</ref>

==Description==
Knapweeds are robust [[weed]]y plants. Their leaves, spiny in some species, are usually deeply divided into elongated lobes at least in the plants' lower part, becoming entire towards the top. The "flowers" (actually [[pseudanthium]] [[inflorescence]]s) are diverse in colour, ranging from intense blues, reds and yellows to any mixture of these and lighter shades towards white. Often, the [[disk flower]]s are much darker or lighter than the [[ray flower]]s, which also differ in [[morphology (biology)|morphology]] and are [[sterile (biology)|sterile]]. Each pseudanthium sits atop a cup- or basket-like cluster of scaly [[bract]]s, hence the name "basketflowers". Many species, in particular those inhabiting more [[arid]] regions, have a long and strong [[taproot]].

[[File:Centaurea nigra-floro.jpg|thumb|left|[[Common knapweed]] (''[[Centaurea nigra|C. nigra]]''), perhaps the single most abundant ''Centaurea'' species of England]]
[[File:Centaurea tchihatcheffii yanardoner sevgi 05668.jpg|thumb|left|''[[Centaurea tchihatcheffii]]'' (locally known as ''Yanardöner''), a highly distinctive and rare knapweed [[endemic]] to Turkey]]

==Ecology==
Certain knapweeds have a tendency to dominate large stretches of landscape together with a few other plants, typically one or two grasses and as many other large herbaceous plants. The [[common knapweed]] (''C. nigra'') for example is plentiful in the [[Mesotrophic grasslands in the British National Vegetation Classification system|mesotrophic grasslands]] of England and nearby regions. It is most prominently found in pastures or meadows dominated by [[cock's-foot]] (''Dactylis glomerata'') as well as either of [[crested dog's-tail]] (''Cynosurus cristatus'') and [[false oat-grass]] (''Arrhenatherum elatius''). It is also often found in mesotrophic grassland on [[rendzina]]s and similar [[calcareous soil]]s in association with [[glaucous sedge]] (''Carex flacca''), [[sheep's fescue]] (''Festuca ovina''), and either [[tor-grass]] (''Brachypodium pinnatum'') and [[rough hawkbit]] (''Leontodon hispidus''), or [[upright brome]] (''Bromus erectus''). In these [[grasslands]], [[greater knapweed]] (''C. scabiosa'') is found much more rarely by comparison, often in association with [[red fescue]] (''Festuca rubra'') in addition to cock's-foot and false oat-grass.

Due to their habit of dominating ecosystems under good conditions, many ''Centaurea'' species can become [[invasive weed]]s in regions where they are not native. In parts of North America, [[diffuse knapweed]] (''C. diffusa''), [[spotted knapweed]] (''C. maculosa'') and [[yellow starthistle]] (''C. solstitialis'') cause severe problems in [[agriculture]] due to their uncontrolled spread. The [[seed]]s are typically transported by human traffic, in particular the [[tire]]s of [[all-terrain vehicle]]s. The two knapweeds are harmful mainly because they are strongly [[allelopathic]], producing powerful [[toxin]]s in their [[root]]s that stunt the growth of plants around them not adapted to this.<ref name = hcv0304>Hierro & Callaway (2003), Vivanco ''et al.'' (2004).</ref> Yellow starthistle, meanwhile, is inedible to most [[livestock]] due to its spines and apparently outright [[poisonous]] to [[horse]]s and other [[equine]]s. However, efficient methods of [[biological control]] by insect [[pest (organism)|pest]]s of these weeds have been developed; the knapweeds can also exploited to their detriment by [[targeted grazing]]. [[Controlled burning]] may also be used, though the timing is important to avoid the plants having seeded already, and neither allowing sufficient time for them to regrow from the rootstock.<ref name = emerygross2005>Emery & Gross (2005).</ref>

Yet other species of ''Centaurea'' &ndash; mostly ones that occur between Italy and the [[Caucasus]] &ndash; are [[endemism|endemics]] of a single island or valley, and some of these are [[endangered]]. The [[Akamas Centaurea]] (''Centaurea akamantis'') of [[Cyprus]] is almost [[extinct]], while the western Caucasus endemics ''[[Centaurea leptophylla|C. leptophylla]]'' and ''[[Centaurea straminicephala|C. straminicephala]]'' are at least very rare and ''[[Centaurea hedgei|C. hedgei]]'' and ''[[Centaurea pecho|C. pecho]]'' from the same region are certainly not abundant either. The last four species would be adversely affected by the proposed [[Yusufeli Dam]], which might actually destroy enough [[habitat]] to push the two rarer ones over the brink of extinction.

[[File:Melitaea phoebe 1815a.jpg|thumb|right|[[Knapweed fritillary]] (''Melitaea phoebe'').<br/>This butterfly can spend their entire lives living off a patch of [[brown knapweed]] (''C. jacea'').]]
''Centaurea'' are copious [[nectar]] producers, especially on high-lime [[soil]]s. The high nectar yield of the genus makes it very attractive to [[insect]]s such as [[butterflies]] &ndash; including the [[endangered]] [[Karner blue]] (''Plebejus melissa samuelis'') which visits introduced spotted knapweed &ndash; and day-flying [[moth]]s &ndash; typically [[Zygaenidae]], such as ''[[Zygaena loti]]'' or the [[six-spot burnet]] (''Z. filipendulae''). The [[larva]]e of some other [[Lepidoptera]] species use ''Centaurea'' species as food plants; see List of Lepidoptera that feed on ''Centaurea''. Several of these are used in biological control of invasive knapweeds and starthistles.

[[Larva]]e of several [[true weevil]]s (Curculionidae) of the [[subfamily]] [[Lixinae]] also feed on ''Centaurea''. Some [[genera]] &ndash; such as ''[[Larinus]]'' whose larval food is flowerheads &ndash; have many species especially [[adaptation|adapted]] to particular knapweeds or starthistle and are used in biological control too. These include the [[yellow starthistle flower weevil]] (''L. curtus'') for yellow starthistle, [[lesser knapweed flower weevil]] (''L. minutus'') for diffuse knapweed and [[blunt knapweed flower weevil]] (''L. obtusus'') for spotted knapweed. [[Broad-nosed seedhead weevil]] (''Bangasternus fausti'') larvae eat diffuse, spotted and [[squarrose knapweed]] (''C. virgata'' ssp. ''squarrosa''), while those of the [[yellow starthistle bud weevil]] (''B. orientalis'') do not seem to live on anything other than yellow starthistle and occasionally [[purple starthistle]] (''C. calcitrapa''). But perhaps most efficient in destroying developing yellow starthistle seedheads is the larva of the [[yellow starthistle hairy weevil]] (''Eustenopus villosus''). [[Knapweed root weevil]] (''Cyphocleonus achates'') larvae bore into the roots of spotted and to a lesser extentely diffuse knapweed, sometimes killing off the entire plant.

Also used in biological control are [[Tephritidae]] (peacock flies) whose larvae feed on ''Centaurea''. [[Knapweed peacock fly]] (''Chaetorellia acrolophi'') larvae eat spotted knapweed and some other species. The [[yellow starthistle peacock fly]] (''C. australis'') has an initial [[generation]] each year which often uses [[cornflower]] (''C. cyanus'') as larval food; later generations switch to yellow starthistle. The flies are generally considered less efficient in destroying the growing seedheads than the weevils, but may be superior under certain conditions; employing flies and weevils in combination is expensive and does not noticeably increase their effect.

==Use by humans==
Despite the negative agricultural and environmental impacts of the more aggressive Centaurea species, there are many ways in which they benefit humans as well. For instance, due to their moderate to high nectar production, which can occur over a comparatively long duration, many species of ''Centaurea'' are popular food sources for [[insect]]s that may otherwise attack certain [[crop]]s.{{Citation needed|date=December 2017}} It may be advisable for some types of farms to allow certain Centaurea species, such as [[cornflower]] (''C. cyanus'') in a European setting, to grow adjacent to fields. These areas are known as [[beetle bank]]s, though they support and attract a diversity of beneficial life beyond beetles. When certain Centaurea species are present, some pests may be drawn away from crops, and predatory insects and [[arachnid]]s that feed upon pest insects will be better-supported by these more naturalized areas. They additionally have the beneficial aspect of supporting [[pollinator]]s, unlike many field crops such as [[maize]]. Moreover, being untreated with [[pesticide]]s and providing more [[Biodiversity|diversity]], plants growing in more wild areas adjacent to farms produce more insects that attract and support birds which can also feed on pests that would harm crops. Insect production is especially high for beetle banks that have enough plants that serve in the role of host plant for immature insects, rather than just in the roles of adult food and/or shelter provision.

Some plants which are considered invasive or problematic in certain areas can have beneficial qualities that outweigh their negative qualities from a human and/or human agricultural point of view, although this sometimes requires some human management – particularly if adequate biological control has not been established for the more aggressive species. An example is wild parsnip, ''[[Pastinaca sativa]]'', which produces florets that feed predatory (and other beneficial) insects as well as large tubular stems that provide winter shelter for native bees, wasps, and other organisms that can be beneficial for agriculture. The plant is considered invasive in some areas of the United States and is also often considered undesirable due to its ability to cause contact skin irritation. However, it also serves as a host plant for the black swallowtail butterfly, helps to bring nutrients up from soils with its deep taproot, and possesses evergreen foliage even in climate zones such as US zone 6. This foliage increases soil warmth and moisture which can be beneficial for certain types of life. Perhaps the most dramatic example of a generally disliked plant's beneficial qualities being usually overlooked is the often-despised ragwort, ''[[Jacobaea vulgaris]]'', which topped the list by a large amount for nectar production in a UK study, with a production per floral unit of (2921 ± 448μg).<ref name=Nectar>{{cite journal |last1=Hicks |first1=DM |last2=Ouvrard |first2=P |last3=Baldock |first3=KCR |title=Food for Pollinators: Quantifying the Nectar and Pollen Resources of Urban Flower Meadows |journal=PLOS ONE |volume=11 |issue=6 |pages=e0158117 |date=2016 |doi=10.1371/journal.pone.0158117 |bibcode=2016PLoSO..1158117H |pmc=4920406 |pmid=27341588 |doi-access=free}}</ref> This very high nectar production, coupled with its early blooming period, makes the plant helpful for the establishment of bee colonies in spring — a period that is often not well-served by commercial flower meadow seed mixes.<ref name=Pollinators>{{cite web |title=Which flowers are the best source of nectar? |publisher=Conservation Grade |url=http://www.conservationgrade.org/2014/10/which_flowers_best_source_nectar/ |access-date=2017-10-18 |date=2014-10-15 |archive-date=2019-12-14 |archive-url=https://web.archive.org/web/20191214024659/http://www.conservationgrade.org/2014/10/which_flowers_best_source_nectar/ |url-status=dead}}</ref> It also has the situationally-beneficial quality of being a spring [[ephemeral]], as well as an annual that lacks difficult-to-combat roots. Plants that provide necessary structural supports for [[invertebrate]] and small [[vertebrate]] [[predator]]s can help to keep overall pest populations low.<ref>Wäckers ''et al.'' (2005)</ref>

[[File:Yellow Star Thistle.jpg|thumb|left|[[Yellow starthistle]] (''C. solstitialis''), an [[invasive weed]] that yields a fine [[honey]]]]
The abundant [[nectar]] produced by ''C. solstitialis'' flowers attracts many [[pollinator]]s. This is another reason for the success of the (situationally) highly [[invasive species]]. Due to genetic differences related to evolutionary adaption, not all members of ''Centaurea'' produce the same amount of nectar. Growing conditions, such as climate and soil, can have a very strong impact, even if the plants grow and flower. For instance, cornflower plants, ''Centaurea cyanus'', produced 33% less seasonal nectar than ''Centaurea nigra'' in a UK study.<ref name=Nectar /> ''C. nigra'' also ranked higher than ragwort in another UK study, although ragwort was still in the top 10 for yearly nectar production.<ref name=Pollinators /> The strong nectar production of certain members of the genus can be exploited to the farmer's advantage, possibly in combination with [[biological control]]. In particular, the [[yellow starthistle]] (''C. solstitialis'') as well as [[spotted knapweed]] (''C. maculosa'') are major [[honey]] plants for [[beekeeper]]s. [[Monofloral honey]] from these plants is light and slightly tangy, and one of the finest honeys produced in the United States &ndash; due to its better availability, it is even fraudulently relabeled and sold as the scarce and expensive [[sourwood]] honey of the [[Appalachian Mountains]]. Placing [[beehive]]s near stands of ''Centaurea'' will cause increased pollination. As most seedheads fail however when biocontrol pests have established themselves, the plants will bloom ever more abundantly in an attempt to replace the destroyed seedheads, to the point where they exhaust their resources in providing food for the pests (seeds), bees ([[pollen]]) and humans (honey). Output of [[allelopathic]] compounds is also liable to be reduced under such conditions &ndash; the plant has to compromise between allocating energy to reproduction and defense. This renders the weeds more likely to be suppressed by native vegetation or crops in the following years, especially if properly timed [[controlled burning]]<ref name=emerygross2005/> and/or [[targeted grazing]] by suitable [[livestock]] are also employed. While yellow starthistle and perhaps other species are [[toxic]] to [[equine]]s, some other livestock may eat the non-spiny knapweeds with relish. In Europe, [[common knapweed]] (''C. nigra'') and globe knapweed (''[[Centaurea macrocephala|C. macrocephala]]'') are locally important pollen sources for honeybees in mid-late summer.

[[8-Hydroxyquinoline]] has been identified as a main allelopathic compound produced by [[diffuse knapweed]] (''C. diffusa''); native North American plants are typically sensitive to it, while those of [[Eastern Europe]] and [[Asia Minor]] usually have [[coevolved]] with the knapweed and are little harmed if at all, aided by native [[microorganism]]s that break down or even feed on the abundantly secreted compound.<ref name=hcv0304/> Thus, 8-hydroxyquinoline is potentially useful to control American plants that have become invasive weeds in the diffuse knapweed's native range.

[[File:Arctiin.svg|thumb|right|[[Arctiin]] from ''[[Centaurea imperialis|C. imperialis]]'' kills [[cancer]] cells in culture]]
Arctiin, found in ''C. imperialis'', has shown [[anticancer]] activity in laboratory studies. The roots of the long-lost ''[[Centaurea foliosa|C. foliosa]]'', an [[endemism|endemic]] of [[Hatay Province]] (Turkey), are used in folk medicine, and other species are presumably too. A South Italian variety{{Verify source|date=April 2011}}<!-- might be ssp, form or even cultivar --> of the [[purple starthistle]] (''C. calcitrapa'') is traditionally consumed by ethnic Albanians ([[Arbëreshë people]]) in the [[Vulture area]] (southern Italy); e.g. in the Arbëreshë communities in [[Lucania]] the young whorls of ''C. calcitrapa'' are boiled and fried in mixtures with other weedy non-cultivated greens. According to research by the Michael Heinrich group at the Centre for Pharmacognosy and Phytotherapy ([[School of Pharmacy, University of London]]) "the [[antioxidant]] activity [...] of the young [[Whorl (botany)|whorls]] of ''Centaurea calcitrapa'', both in the [[DPPH]] and in the [[lipid peroxidation]] inhibition assays, [is] very interesting and [the] species should be investigated phytochemically and biochemically focusing on these properties". Extracts from ''C. calcitrapa'' were furthermore found to have significant [[xanthine oxidase]] (XO)-inhibiting activity.<ref>Pieroni ''et al.'' (2002).</ref>

Spotted knapweed as well as other species are rich in [[cnicin]], a [[bitter (taste)|bitter]] compound found mainly in the leaves and often used to flavor the [[digestif]] [[amaro (drink)|amaro]]. In western [[Crete]], [[Greece]] a local [[variety (botany)|variety]]{{Verify source|date=April 2011}}<!-- might be ssp, form or even cultivar --> of ''C. calcitrapa'' called ''{{lang|grc-Latn|gourounaki}}'' ({{lang|grc|γουρουνάκι}} "little pig") also has its leaves eaten boiled by the locals. In the same island an endemic local species, ''[[Centaurea idaea|C. idaea]]'' called ''{{lang|grc-Latn|katsoula}}'' ({{lang|grc|κατσούλα}}), ''{{lang|grc-Latn|tsita}}'' ({{lang|grc|τσίτα}}) or ''{{lang|grc-Latn|aspragatha}}'' ({{lang|grc|ασπραγκάθα}}), has its leaves eaten boiled by the locals too.<ref>Stavridakis (2006)</ref>

{{color swatch|#6495ED|[[Cornflower]] blue|left}}
Some species are cultivated as [[ornamental plant]]s in [[garden]]s. As regards other aspects of [[popular culture]], [[cornflower]] (''C. cyanus'') is the [[floral emblem]] of [[Östergötland]] province (Sweden) &ndash; where is it called ''blåklint'', literally "blue mountain" &ndash; and of [[Päijänne Tavastia]] region in [[Finland]], where it is known as ''ruiskaunokki'' ("[[rye]]-beaks") or ''ruiskukka'' ("rye-flower"). It is also the national flower of [[Estonia]] where its local name ''rukkilill'' means "rye-[[lily]]", [[Belarus]] where it is called ''vałoška'' ({{langx|be|валошка}}), and one of those of Germany where it is called ''Kornblume'' ("cornflower"). The origin of the name "[[caltrop]]" for the ancient low-tech [[area denial]] weapon is probably in some way connected with ''C. calcitrapa'' and its spiny seeds. This plant is attested to by the colloquial name "caltrop" at a time when the weapons were still called by their [[Ancient Rome|Roman]] name ''tribulus''.<ref>In reference to their resemblance to the spiny seeds of the [[puncture vine]], later named ''Tribulus terrestris''.</ref> Lastly, the [[color]] [[cornflower blue]] is named after ''C. cyanus''. Cornflower is also used as a cut flower.

==Systematics and taxonomy==
[[File:Centaurea horrida Sardinia LM022.jpg|thumb|''[[Centaurea horrida]]'']]
As namesake member of the [[subtribe]] [[Centaureinae]] of [[tribe (biology)|tribe]] [[Cardueae]], the knapweeds are probably most closely related to genera such as ''[[Carthamus]]'' (distaff thistles), ''[[Cnicus]]'' (blessed thistle), ''[[Crupina]]'' (crupinas) or ''[[Notobasis]]'' (Syrian thistle), and somewhat less closely to most other [[thistle]]s. The [[monotypic]] ''Cnicus'' seems in fact to properly belong in ''Centaurea''.<ref>Panero & Funk (2002), Keil (2006), Keil & Ochsmann (2006).</ref>

Research in the late 20th century shows that ''Centaurea'' as traditionally defined is [[polyphyletic]]. A number of 19th- and 20th-century efforts to reorganize the genus were not successful, and it is not yet clear what the consequences of the recent research will be for classification of this genus and other related genera. The [[type species]] ''[[Centaurea centaurium|C. centaurium]]'' stands somewhat apart from the main lineage of knapweeds and thus the [[Taxonomy (biology)|taxonomic]] consequences of a rearrangement might be severe, with hundreds of species needing to be moved to new genera. It has thus been proposed to change the type species to one of the main lineages to avoid this problem. What seems certain however is that the basketflowers &ndash; presently treated as a [[section (botany)|section]] ''Plectocephalus'' &ndash; will be reinstated as a distinct genus in the near future. The [[rock-centauries]] (''Cheirolophus''), formerly usually included in ''Centaurea'', are now already treated as separate genus.<ref name=kko2006/>

<gallery>
File:Centaurea macrocephala cropped-2832.jpg|Globe knapweed (''[[Centaurea macrocephala|C. macrocephala]]'')
File:Centaurea napifolia Sardinia LM.jpg|''[[Centaurea napifolia]]''
File:Centaurea nervosa (fabrizio.binello).jpg|''[[Centaurea nervosa]]''
File:Centaurea pseudophrygia DSCF1538.JPG|''[[Centaurea pseudophrygia]]''
File:Centaurea pulcherrima0.jpg|''[[Centaurea pulcherrima]]''
File:Centaurea triumfettii.jpeg|''[[Centaurea triumfettii]]''
File:0 Centaurea uniflora - Centaurée à un capitule.JPG|''[[Centaurea uniflora]]''
</gallery>
==Species==
{{Main|List of Centaurea species|l1=List of ''Centaurea'' species}}
Better-known ''Centaurea'' species include:
{{div col|colwidth=15em}}
* ''[[Centaurea acaulis]]''
* ''[[Centaurea adpressa]]''
* ''[[Centaurea aegyptiaca]]''
* ''[[Centaurea aeolica]]''
* ''[[Centaurea aggregata]]''
* ''[[Centaurea akamantis]]'' &ndash; Akamas centaurea
* ''[[Centaurea alba]]''
* ''[[Centaurea albonitens]]'' <small>Turrill</small>
* ''[[Centaurea alpestris]]''
* ''[[Centaurea alpina]]''
* ''[[Centaurea ambigua]]''
* ''[[Centaurea amblyolepis]]''
* ''[[Centaurea americana]]'' &ndash; American basketflower, American starthistle
* ''[[Centaurea ammocyanus]]''
* ''[[Centaurea antennata]]'' <small>Dufour</small>
* ''[[Centaurea antiochia]]'' <small>Boiss.</small>
* ''[[Centaurea aplolepa]]''
** ''Centaurea aplolepa'' subsp. ''carueliana''
* ''[[Centaurea appendicigera]]'' <small>C.Koch</small><!-- endemic to Turkey -->
* ''[[Centaurea argentea]]''
* ''[[Centaurea ascalonica]]''
* ''[[Centaurea aspera]]'' <small>L.</small> &ndash; rough starthistle
* ''[[Centaurea atacamensis]]'' <small>(Reiche) I.M.Johnst.</small>
* ''[[Centaurea atropurpurea]]''
* ''[[Centaurea ×aurata]]''
* ''[[Centaurea babylonica]]'' <small>L.</small>
* ''[[Centaurea balsamita]]''
* ''[[Centaurea behen]]'' <small>L.</small> &ndash; ''ak behmen'' ([[Turkish language|Turkish]])
* ''[[Centaurea bella]]''
* ''[[Centaurea benedicta]] &ndash; ''Cnicus''
* ''[[Centaurea bieberseinii]]''
* ''[[Centaurea borjae]]''
* ''[[Centaurea bovina]]''
* ''[[Centaurea bracteata]]''
* ''[[Centaurea brevifimbriata]]'' <small>Hub.-Mor.</small>
* ''[[Centaurea bulbosa]]''
* ''[[Centaurea busambarensis]]'' <small>Guss.</small>
* ''[[Centaurea cachinalensis]]''
* ''[[Centaurea calcitrapa]]'' &ndash; purple starthistle, red starthistle, "[[caltrop]]"
* ''[[Centaurea calcitrapoides]]''
* ''[[Centaurea cariensis]]'' <small>Boiss.</small>
* ''[[Centaurea cariensiformis]]'' <small>Hub.-Mor.</small>
* ''[[Centaurea caroli-henrici]]'' <small>Gabrieljan & Dittrich</small>
* ''[[Centaurea centaurium]]'' <small>L.</small><!-- type species -->
* ''[[Centaurea chilensis]]''
* ''[[Centaurea cineraria]]''  &ndash; velvet centaurea, dusty miller
* ''[[Centaurea clementei]]''
* ''[[Centaurea collina]]'' <small>L.</small>
* ''[[Centaurea corymbosa]]''
* ''[[Centaurea crithmifolia]]''
* ''[[Centaurea crocodylium]]''
* ''[[Centaurea cyanoides]]'' <small>J.Berggr. & Wahlenb.</small>
* ''[[Centaurea cyanus]]'' &ndash; cornflower, bachelor's button, boutonniere flower, hurtsickle, bluebottle, basketflower
* ''[[Centaurea damascena]]''
* ''[[Centaurea debeauxii]]'' <small>Gren. & Godr.</small>
* ''[[Centaurea demirizii]]'' <small>Wagenitz</small>
* ''[[Centaurea depressa]]'' &ndash; low cornflower
* ''[[Centaurea deusta]]''
* ''[[Centaurea diffusa]]'' &ndash; diffuse knapweed, white knapweed, tumble knapweed
* ''[[Centaurea diluta]]'' &ndash; North African knapweed
* ''[[Centaurea drabifolia]]'' <small>Sm.</small>
* ''[[Centaurea drabifolioides]]'' <small>Hub.-Mor.</small>
* ''[[Centaurea dschungarica]]''
* ''[[Centaurea emilae Hüseynova et Qaraxani]]''<ref>[https://archive.today/20140604060450/http://www.science.gov.az/az/index.php?id=7271 AMEA Botanika İnstitutunun əməkdaşları Azərbaycan florasında yeni növ aşkarlayıblar.] science.gov.az</ref>
* ''[[Centaurea eriophora]]''
* ''[[Centaurea eryngioides]]''
* ''[[Centaurea filiformis]]''
* ''[[Centaurea fischeri]]'' <small>Willd.</small>
* ''[[Centaurea floccosa]]''
* ''[[Centaurea foliosa]]'' <small>Boiss. & Kotschy</small><!-- AnnalenDesNaturhistorischenMuseumsWienB98:175 -->
* ''[[Centaurea forojuliensis]]''
* ''[[Centaurea friderici]]'' <small>Vis.</small> &ndash; ''palagruška zečina'' ([[Croatian (language)|Croatian]])
* ''[[Centaurea gayana]]''
* ''[[Centaurea gigantea]]''
* ''[[Centaurea glaberrima]]'' <small>Tausch</small>
* ''[[Centaurea glastifolia]]''
* ''[[Centaurea grinensis]]''
* ''[[Centaurea gymnocarpa]]''
* ''[[Centaurea haradjianii]]'' <small>Wagenitz</small>
* ''[[Centaurea hedgei]]''
* ''[[Centaurea helenioides]]'' <small>Boiss.</small>
* ''[[Centaurea hermannii]]'' <small>F.Hermann</small>
* ''[[Centaurea horrida]]'' <small>Badarò</small> &ndash; ''fiordaliso spinoso'' ([[Italian (language)|Italian]])
* ''[[Centaurea hyalolepis]]''
* ''[[Centaurea hypoleuca]]''
* ''[[Centaurea iberica]]'' &ndash; Iberian starthistle, Iberian knapweed
* ''[[Centaurea idaea]]'' &ndash; ''katsoula'', ''tsita'' ([[Cretan Greek]])
* ''[[Centaurea imperialis]]'' <small>Hausskn. ex Bornm.</small>
* ''[[Centaurea jabukensis]]''
* ''[[Centaurea jacea]]'' &ndash; brown knapweed, brownray knapweed
* ''[[Centaurea kasakorum]]''
* ''[[Centaurea kopetaghensis]]''
* ''[[Centaurea kotschyana]]'' <small>Heuff.</small>
* ''[[Centaurea lanulata]]''
* ''[[Centaurea leptophylla]]''
* ''[[Centaurea leucophylla]]''
* ''[[Centaurea limbata]]''
* ''[[Centaurea lydia]]'' <small>Boiss.</small>
* ''[[Centaurea macrocephala]]'' <small>Puschk. ex Willd.</small> &ndash; globe knapweed, Armenian basketflower
* ''[[Centaurea maculosa]]'' &ndash; spotted knapweed (might belong in ''C. stoebe'' subsp. ''micranthos'')
* ''[[Centaurea mannagettae]]''
* ''[[Centaurea margaritalba]]'' <small>Klok.</small><!-- = C. margaritacea Schmalh. -->
* ''[[Centaurea marschalliana]]''
* ''[[Centaurea melitensis]]'' &ndash; Maltese starthistle; ''tocalote, tocolote'' ([[California]])
* ''[[Centaurea minor]]''
* ''[[Centaurea moschata]]'' &ndash; sweet sultan
* ''[[Centaurea ×moncktonii]]'' <small>C.E.Britton</small> &ndash; meadow knapweed, protean knapweed (= ''C. ×pratensis'' <small>Thuill non Salisb.</small>)
* ''[[Centaurea monocephala]]''
* ''[[Centaurea montana]]'' &ndash; montane knapweed, perennial cornflower, mountain cornflower, mountain bluet
* ''[[Centaurea napifolia]]'' <small>L.</small> &ndash; ''fiordaliso romano'' (Italian)<!-- = C. romana -->
* ''[[Centaurea nervosa]]'' <small>Rchb. ex Steud.</small>
* ''[[Centaurea nigra]]'' &ndash; common knapweed, black knapweed, lesser knapweed, hardheads
* ''[[Centaurea nigrescens]]'' &ndash; Tyrol knapweed, short-fringed knapweed, Tyrol thistle
* ''[[Centaurea nigrifimbria]]'' <small>(C.Koch) Sosn.</small>
* ''[[Centaurea nivea]]'' <small>(Bornm.) Wagenitz</small>
* ''[[Centaurea onopordifolia]]''
* ''[[Centaurea orientalis]]'' <small>L.</small>
* ''[[Centaurea ornata]]'' <small>Willd.</small>
* ''[[Centaurea ovina]]''
* ''[[Centaurea pallescens]]'' <small>Delile</small>
* ''[[Centaurea paniculata]]'' <small>L.</small>
* ''[[Centaurea parlatoris]]''
* ''[[Centaurea pecho]]''
* ''[[Centaurea phrygia]]'' &ndash; wig knapweed
* ''[[Centaurea pindicola]]''
* ''[[Centaurea polypodiifolia]]''
* ''[[Centaurea ×pratensis]]'' <small>Salisb.</small> (''C. jacea × C. nigra'') &ndash; meadow knapweed
* ''[[Centaurea procurrens]]''
* ''[[Centaurea ×psammogena]]'' <small>G.Gayer.</small> (''C. diffusa × C. stoebe'' subsp. ''micranthos'')
* ''[[Centaurea pseudocaerulescens]]''
* ''[[Centaurea pseudophrygia]]'' <small>C.A.Mey.</small>
* ''[[Centaurea pulcherrima]]'' <small>Willd.</small>
* ''[[Centaurea pullata]]'' <small>L.</small>
* ''[[Centaurea pumilio]]''
* ''[[Centaurea ragusina]]'' <small>L.</small>
* ''[[Centaurea rigida]]''
* ''[[Centaurea rothrockii]]'' <small>Greenm.</small> &ndash; Mexican basketflower, Rothrock's basketflower, Rothrock's knapweed<!-- = Plectocephalus rothrockii -->
* ''[[Centaurea ruthenica]]''
* ''[[Centaurea rutifolia]]'' <small>Sm.</small>
* ''[[Centaurea sadleriana]]'' &ndash; Pannonian knapweed
* ''[[Centaurea salicifolia]]'' <small>Bieb. ex Willd.</small>
* ''[[Centaurea scabiosa]]'' &ndash; greater knapweed
* ''[[Centaurea scannensis]]''
* ''[[Centaurea scoparia]]''
* ''[[Centaurea scopulorum]]'' <small>Boiss. & Heldr.</small>
* ''[[Centaurea seguenzae]]''
* ''[[Centaurea seridis]]'' <small>L.</small>
* ''[[Centaurea sibirica]]''
* ''[[Centaurea simplicicaulis]]''
* ''[[Centaurea sinaica]]''
* ''[[Centaurea solstitialis]]'' &ndash; yellow starthistle, golden starthistle, yellow cockspur, St. Barnaby's thistle, Barnaby thistle
* ''[[Centaurea speciosa]]''
* ''[[Centaurea sphaerocephala]]'' <small>L.</small><!-- = Centaurea corsica Gand., Centaurea fontanesii Durieu. "sphaerocephalum" is lapsus -->
* ''[[Centaurea stenolepis]]''
* ''[[Centaurea stoebe]]'' <small>L.</small>
** ''Centaurea stoebe'' subsp. ''micranthos'' <small>(Gugler) Hayek</small>
* ''[[Centaurea straminicephala]]''
* ''[[Centaurea sulphurea]]'' &ndash; Sicilian starthistle
* ''[[Centaurea tauromenitana]]'' <small>Guss.</small>
* ''[[Centaurea tenoreana]]''
* ''[[Centaurea tommasinii]]''
* ''[[Centaurea transalpina]]'' <small>Schleich. ex DC.</small>
* ''[[Centaurea tchihatcheffii]]'' &mdash; ''yanardöner'' ([[Turkish language|Turkish]])
* ''[[Centaurea trichocephala]]'' <small>Bieb. ex Willd.</small> &ndash; featherhead knapweed
* ''[[Centaurea triniifolia]]''
* ''[[Centaurea triumfettii]]'' <small>All.</small><!-- "triumphetti" is lapsus -->
* ''[[Centaurea tymphaea]]<small>Hausskn.</small><ref>[https://powo.science.kew.org/results?q=Centaurea%20tymphaea ''Centaurea tymphaea''] Plants of the World Online</ref>
* ''[[Centaurea ucriae]]'' <small>Lacaita</small>
* ''[[Centaurea uniflora]]'' <small>Turra</small>
* ''[[Centaurea verbascifolia]]'' <small>Vahl</small>
* ''[[Centaurea verutum]]'' <small>L.</small>
* ''[[Centaurea virgata]]''
** ''Centaurea virgata'' subsp. ''squarrosa'' &ndash; squarrose knapweed
* ''[[Centaurea wiedemanniana]]'' <small>Fisch. & Mey.</small>
* ''[[Centaurea yozgatensis]]'' <small>Wagenitz</small>
{{div col end}}

===Formerly placed here===
Plant species formerly placed in ''Centaurea'' include:{{cn|date=November 2024}}
* ''[[Acroptilon repens]]'' &ndash; Russian knapweed (as ''Centaurea repens'')
* ''[[Cheirolophus crassifolius]]'' &ndash; Maltese rock-centaury (as ''Centaurea crassifolia, C. spathulata'')
* ''[[Femeniasia balearica]]'' (as ''Centaurea balearica'')
* ''[[Volutaria muricata]]'' (as ''Centaurea muricata'')

==Footnotes==
{{Reflist}}

==References==
* {{aut|Emery, S.M. & Gross, K.L.}} (2005): Effects of timing of prescribed fire on the demography of an invasive plant, spotted knapweed ''Centaurea maculosa''. ''[[Journal of Applied Ecology|J. Appl. Ecol.]]'' '''42'''(1): 60-69. <small>{{doi|10.1111/j.1365-2664.2004.00990.x}}</small> (HTML abstract)
* {{aut|Hierro. J.L. & Callaway, R.M.}} (2003): Allelopathy and exotic plant invasion. ''[[Plant and Soil]]'' '''256'''(1): 29–39. <small>{{doi|10.1023/A:1026208327014}}</small> [https://web.archive.org/web/20090116201203/http://plantecology.dbs.umt.edu/Full%20text%20papers%20and%20abstracts/2003%20papers/PlantandSoil200329to39.pdf PDF fulltext]
* {{aut|Keil, David J.}} (2006): 21. ''Plectocephalus. In: [[Flora of North America North of Mexico]]'' Vol. 19 (Magnoliophyta: Asteridae, part 6: Asteraceae, part 1). Oxford University Press. <small>{{ISBN|0-19-530563-9}}</small> [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=125862 HTML fulltext]
* {{aut|Keil, David J. & Ochsmann, J.}} (2006): 24. ''Centaurea. In: [[Flora of North America North of Mexico]]'' Vol. 19 (Magnoliophyta: Asteridae, part 6: Asteraceae, part 1). Oxford University Press. <small>{{ISBN|0-19-530563-9}}</small> [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=106012 HTML fulltext]
* {{aut|Panero, J.L. & Funk, V.A.}} (2002): Toward a phylogenetic subfamilial classification for the Compositae (Asteraceae). ''[[Proceedings of the Biological Society of Washington|Proc. Biol. Soc. Wash.]]'' '''115'''(4): 909–922. [http://si-pddr.si.edu/jspui/bitstream/10088/11384/1/bot_2002_pr_Panero_Funk_SubfamilialCompositae.pdf PDF fulltext] {{Webarchive|url=https://web.archive.org/web/20120327045433/http://si-pddr.si.edu/jspui/bitstream/10088/11384/1/bot_2002_pr_Panero_Funk_SubfamilialCompositae.pdf |date=2012-03-27 }}
* {{aut|Pieroni, A.; Janiak, V.; Dürr, C.M.; Lüdeke, S.; Trachsel E. & Heinrich, M.}} (2002): ''In vitro'' Antioxidant Activity of Non-cultivated Vegetables of Ethnic Albanians in Southern Italy. ''[[Phytotherapy Research|Phytother. Res.]]'' '''16'''(5): 467–473. <small>{{doi|10.1002/ptr.1243}}</small> [https://web.archive.org/web/20110718171601/http://www.andreapieroni.eu/Pieroni%20et%20al.%2C%202002d.pdf PDF fulltext]
* {{aut|Stavridakis, Kleonikos G.}} (Κ. Γ. Σταυριδάκης) (2006): ''Wild edible plants of Crete'' - Η Άγρια βρώσιμη χλωρίδα της Κρήτης [English and Greek]. Rethymnon Crete. <small>{{ISBN|960-631-179-1}}</small>
* {{aut|Vivanco, J.M.; Bais, H.P.; Stermitz, F.R.; Thelen, G.C. & Callaway, R.M.}} (2004): Biogeographical variation in community response to root allelochemistry: Novel weapons and exotic invasion. ''[[Ecology Letters|Ecol. Lett.]]'' '''7'''(4): 285–292. <small>{{doi|10.1111/j.1461-0248.2004.00576.x}}</small> [https://web.archive.org/web/20081013110042/http://lamar.colostate.edu/~jvivanco/papers/Ecol_lett/Vivanco_2004.pdf PDF fulltext] [https://web.archive.org/web/20120930101424/http://www.blackwellpublishing.com/products/journals/suppmat/ELE/ELE576/ELE576sm.htm Supplementary material]
* {{aut|Wäckers, Felix; van Rijn, Paul & Bruin, Jan}} (2005): ''Plant-Provided Food for Carnivorous Insects - a protective mutualism and its applications''. Cambridge University Press, UK. <small>{{ISBN|978-0-521-81941-1}}</small> [https://books.google.com/books?id=7j1WyqPAARwC Preview] at [[Google Books]]

==Further reading==
{{More footnotes|date=January 2009}}
* Mabberley, D.J. 1987. ''The Plant Book. A portable dictionary of the higher plants''. Cambridge University Press, Cambridge. 706 p.&nbsp;{{ISBN|0-521-34060-8}}.
* Robbins, W.W., M. K. Bellue, and W. S. Ball. 1970. ''Weeds of California''. State of California, Dept. of Agriculture. 547 p.

==External links==
*{{Commons-inline|2=''Centaurea''}}
*{{Commons category-inline|2=''Centaurea'' (category)}}
*[https://web.archive.org/web/20190828212649/http://centaurea.net/ ''Centaurea'' images]
*[http://rbg-web2.rbge.org.uk/cgi-bin/nph-readbtree.pl/feout?FAMILY_XREF=&GENUS_XREF=Centaurea&SPECIES_XREF=&TAXON_NAME_XREF=&RANK= Flora Europaea: ''Centaurea'']
*[http://www.efloras.org/florataxon.aspx?flora_id=3&taxon_id=106012 Flora of China: ''Centaurea'' species list]
*[http://flora.huh.harvard.edu/FloraData/060/PDF/V04/Volume4-Part2_Centaurea.pdf Flora of Chile: ''Centaurea'' (pdf)]

{{Taxonbar|from=Q156414}}
{{Authority control}}

[[Category:Centaurea| ]]
[[Category:Asteraceae genera]]
[[Category:Taxa named by Carl Linnaeus]]