Centaurea - AbsoluteAstronomy.com

"Basket flower" and spelling variants redirect here. In Australia, this usually means the unrelated plant Adenanthos obovatus

Adenanthos obovatus

Adenanthos obovatus, commonly known as basket flower or jugflower, is a shrub of the Proteaceae family endemic to Southwest Australia. Described by French naturalist Jacques Labillardière in 1805, it had been first collected by Archibald Menzies in 1791...

Centaurea (icon "Cen-tau-ré-a

Syllable stress of Botanical Latin

Syllable stress of botanical names varies with the language spoken by the person using the botanical name. In English-speaking countries the Botanical Latin places syllable stress for botanical names derived from ancient Greek and Latin broadly according to two systems, either the Reformed...

") is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

of between 350 and 600 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

of herb

Herb

Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...

aceous thistle

Thistle

Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...

-like flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

s in the family Asteraceae

Asteraceae

The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...

. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere

Eastern Hemisphere

The Eastern Hemisphere, also Eastern hemisphere or eastern hemisphere, is a geographical term for the half of the Earth that is east of the Prime Meridian and west of 180° longitude. It is also used to refer to Europe, Asia, Africa, and Australasia, vis-à-vis the Western Hemisphere, which includes...

; the Middle East

Middle East

The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

and surrounding regions are particularly species-rich. Common names for this genus are starthistles, knapweeds, centaureas and the more ambiguous "bluets"; a vernacular name used for these plants in parts of England is "loggerhead
Loggerhead
-Locations:* Loggerhead Key, the largest islet in the Dry Tortugas, Florida* Loggerheads, Denbighshire, a village in Denbighshire, Wales* Loggerheads, Staffordshire, a small village in north Staffordshire, England...

s". The Plectocephalus group – possibly a distinct genus – is known as basketflowers. "Cornflowers" is used for a few species, but that term more often specifically means C. cyanus (sometimes also called "Basket Flower"). And while one sometimes finds the name "centauries", this properly refers to the unrelated plant genus Centaurium
Centaurium
Centaurium is a genus of 20 species in the gentian family , tribe Chironieae, subtribe Chironiinae. The genus was named after the centaur Chiron, famed in Greek mythology for his skill in medicinal herbs...

.

Description and ecology

Knapweeds are robust weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

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

Pseudanthium

A pseudanthium or flower head is a special type of inflorescence, in which several flowers are grouped together to form a flower-like structure. The real flowers are generally small and greatly reduced, but can sometimes be quite large...

inflorescence

Inflorescence

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

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 flowers are much darker or lighter than the ray flowers, which also differ in morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

and are sterile. Each pseudanthium sits atop a cup- or basket-like cluster of scaly bract

Bract

In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...

s, hence the name "basketflowers". Many species, in particular those inhabiting more arid

Arid

A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

regions, have a long and strong taproot

Taproot

A taproot is an enlarged, somewhat straight to tapering plant root that grows vertically downward. It forms a center from which other roots sprout laterally.Plants with taproots are difficult to transplant...

Certain knapweeds have a tendency to dominate large stretches of landscape together with a few other plants, typically one or two grass

Grass

Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

es and as many other large herbs. The Common Knapweed (C. nigra
Centaurea nigra
Centaurea nigra is a species of flowering plant in the daisy family known by the common names Lesser Knapweed, Common Knapweed and Black Knapweed...

) for example is plentiful in the 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

Rendzina

Rendzina is a dark, grayish-brown, humus-rich, intrazonal soil. It is one of the soils most closely associated with the bedrock type and an example of initial stages of soil development...

s and similar calcareous soils in association with Glaucous Sedge (Carex flacca), Sheep's Fescue

Sheep's Fescue

Sheep's Fescue or Sheep Fescue is a species of grass.-General Description:It is a perennial plant sometimes found in acidic ground, for example in the Portlethen Moss, Scotland and mountain pasture, throughout Europe and eastwards across much of Asia; it has also been introduced to North...

(Festuca ovina), and either Tor-grass

Tor-grass

Tor-grass is a plant in the grass family, with a widespread distribution in temperate regions of the Northern Hemisphere. It typically grows in calcareous grassland, and reaches 70–120 cm tall. The flowerhead is open, with 10 to 15 erect spikelets.The caterpillars of some Lepidoptera use it...

(Brachypodium pinnatum) and Rough Hawkbit (Leontodon hispidus), or Upright Brome (Bromus erectus
Bromus erectus
Bromus erectus, commonly known as either upright brome or meadow brome, is a dense, course, tufted perennial grass. It can grow to 120cm. Like many brome grasses the plant is hairy.-Description:...

). In these grasslands, Greater Knapweed (C. scabiosa) is found much more rarely by comparison, often in association with Red Festuce (F. rubra) in addition to Cock's-foot, False Oat-grass.

Due to their habit of dominating ecosystems under good conditions, many Centaurea species can become invasive weeds in regions where they are not native. In parts of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, Diffuse Knapweed

Diffuse knapweed

Diffuse Knapweed , also known as White Knapweed or Tumble Knapweed, is a member of the genus Centaurea in the family Asteraceae. It is native to Asia Minor , the Balkans, , Ukraine, and southern Russia. Diffuse knapweed is an annual or biennial plant, generally growing to between 10 and 60 cm...

(C. diffusa), Spotted Knapweed (C. maculosa) and Yellow Starthistle

Yellow starthistle

Centaurea solstitialis, yellow star-thistle, is a member of the Asteraceae family, native to the Mediterranean Basin region. The plant is also known as golden starthistle, yellow cockspur and St...

(C. solstitialis) cause severe problems in agriculture

Agriculture

Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

due to their uncontrolled spread. The seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s are typically transported by human traffic, in particular the tire

Tire

A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

s of all-terrain vehicle

All-terrain vehicle

An all-terrain vehicle , also known as a quad, quad bike, three wheeler, or four wheeler, is defined by the American National Standards Institute as a vehicle that travels on low pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control...

s. The two knapweeds are harmful mainly because they are strongly allelopathic, producing powerful toxin

Toxin

A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...

s in their root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s that stunt the growth of plants around them not adapted to this. Yellow Starthistle, meanwhile, is inedible to most livestock

Livestock

Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

due to its spines and apparently outright poisonous to horse

Horse

The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

s and other equines. However, efficient methods of biological control by insect pests of these weeds have been developed; the knapweeds can also exploited to their detriment by targeted grazing

Targeted grazing

Targeted grazing is the use of domestic livestock to change the composition and structure of vegetation to meet management goals. This technique is often used in combination with other vegetation management treatments such as prescribed fire, seeding, chemical application, or mechanical means...

. 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.

Yet other species of Centaurea – mostly ones that occur between Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

and the Caucasus

Caucasus

The Caucasus, also Caucas or Caucasia , is a geopolitical region at the border of Europe and Asia, and situated between the Black and the Caspian sea...

– are endemics of a single island or valley, and some of these are endangered. The Akamas Centaurea (Centaurea akamantis) of Cyprus

Cyprus

Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...

is almost extinct, while the western Caucasus endemics C. leptophylla and C. straminicephala are at least very rare and C. hedgei and C. pecho from the same region are certainly not abundant either. The last four species would be adversely affected by the proposed Yusufeli Dam

Yusufeli Dam

The Yusufeli Dam is a proposed embankment dam on the Çoruh River near Yusufeli in Artvin Province within the eastern Black Sea region of Turkey. The Yusufeli Dam will be the second largest dam within the larger Çoruh River Development Plan which plans to build 13 dams, of which 2 are operational...

, which might actually destroy enough habitat

Habitat

* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

to push the two rarer ones over the brink of extinction.
Centaurea are copious nectar producers, especially on high-lime soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

s. The high nectar yield of the genus makes it very attractive to insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s such as butterflies – including the endangered Karner Blue

Karner Blue

The Karner Blue, Lycaeides melissa samuelis, is a small, blue butterfly found in small areas of New Jersey, the Great Lakes region, southern New Hampshire, and the Capital District region of New York. The butterfly, whose lifecycle depends on the wild blue lupine flower , is classified as an...

(Lycaeides melissa samuelis) which visits introduced Spotted Knapweed – and day-flying moth

Moth

A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...

s – typically Zygaenidae

Zygaenidae

The Zygaenidae moths are a family of Lepidoptera. The majority of zygaenids are tropical, but they are nevertheless quite well represented in temperate regions. There are about 1000 species. Various species are commonly known as Burnet or Forester moths, often qualified by the number of spots,...

, such as Zygaena loti
Zygaena loti
Zygaena loti is a member of the Zygaenidae family....

or the Six-spot Burnet

Six-spot Burnet

The Six-spot Burnet, Zygaena filipendulae, is a day-flying moth of the family Zygaenidae. It is a common species throughout Europe....

(Z. filipendulae). The larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e of some other Lepidoptera

Lepidoptera

Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

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

Larva

e of several true weevils (Curculionidae) of the subfamily Lixinae

Lixinae

Lixinae is a subfamily of true weevils, included in the Molytinae in many older treatments. They are mainly root feeders, although some develop in flower buds or stems. Several species are used in biological control of invasive weeds, namely knapweeds .Characteristics include tarsal claws that are...

also feed on Centaurea. Some genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

– such as Larinus
Larinus
Larinus is a genus of true weevils, comprising about 180 species, mostly in the Palaearctic region. Turkey appears to have a significant diversity of the group, with more than 50 species recorded in the Eastern part of the country....

whose larval food is flowerheads – have many species especially adapted

Adaptation

An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

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

Tephritidae

Tephritidae is one of two fly families referred to as "fruit flies", the other family being Drosophilidae. Tephritidae does not include the biological model organisms of the genus Drosophila , which is often called the "common fruit fly". There are nearly 5,000 described species of tephritid...

(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

Generation

Generation , also known as procreation in biological sciences, is the act of producing offspring....

each year which often uses Cornflower

Cornflower

Centaurea cyanus is a small annual flowering plant in the family Asteraceae, native to Europe. "Cornflower" is also erroneously used for chicory, and more correctly for a few other Centaurea species; to distinguish C...

(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

Though the overall effect of the entire genus on humans is probably detrimental, this is merely due to the considerable damage done by a handful of species when these are allowed to spread uncontrolled. On a per-species basis, most centaureas are inoffensive and at least pleasant-looking plants. As noted above, many species of Centaurea are popular food for insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s that may otherwise attack crop

Crop

Crop may refer to:* Crop, a plant grown and harvested for agricultural use* Crop , part of the alimentary tract of some animals* Crop , a modified whip used in horseback riding or disciplining humans...

s; particular in small-scale farming it is often advisable to allow non-invasive species (like Cornflower

Cornflower

, C. cyanus, in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

) to grow around fields. In such a beetle bank

Beetle bank

A Beetle bank, In agriculture and horticulture, is a form of biological pest control. It is a strip planted with grasses and-or perennial plants, within a crop field or a garden, that fosters and provides habitat for beneficial insects, birds, and other fauna that prey on...

, they will draw pests away from crops, and at the same time by their robust structure provide shelter for invertebrate

Invertebrate

An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

and small vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

predators that will keep overall pest populations low.

The abundant nectar produced by Centaurea flowers attracts many pollinator

Pollinator

A pollinator is the biotic agent that moves pollen from the male anthers of a flower to the female stigma of a flower to accomplish fertilization or syngamy of the female gamete in the ovule of the flower by the male gamete from the pollen grain...

s. This is another reason for the success of the highly invasive species

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

, but as it holds true for the entire genus it is not decisive. Yet it can be exploited to the farmer's advantage in combination with biological control of these weeds: In particular the Yellow Starthistle

Yellow starthistle

Centaurea solstitialis, yellow star-thistle, is a member of the Asteraceae family, native to the Mediterranean Basin region. The plant is also known as golden starthistle, yellow cockspur and St...

(C. solstitialis) as well as Spotted Knapweed (C. maculosa) are major honey

Honey

Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

plants for beekeeper

Beekeeper

A beekeeper is a person who keeps honey bees for the purposes of securing commodities such as honey, beeswax, pollen, royal jelly; pollinating fruits and vegetables; raising queens and bees for sale to other farmers; and/or for purposes satisfying natural scientific curiosity...

s. Monofloral honey

Monofloral honey

Monofloral honey is a type of honey which has a high value in the marketplace because it has a distinctive flavor or other attribute due to its being predominantly from the nectar of one plant species....

from these plants is light and slightly tangy, and one of the finest honeys produced in the USA – due to its better availability, it is even fraudulently relabeled and sold as the scarce and expensive Sourwood

Sourwood

Sourwood or sorrel tree is the sole species in the genus Oxydendrum, in the family Ericaceae. It is native to eastern North America, from southern Pennsylvania south to northwest Florida and west to southern Illinois; it is most common in the lower chain of the Appalachian Mountains...

honey of the Appalachian Mountains

Appalachian Mountains

The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...

. Placing beehive

Beehive

A beehive is a structure in which bees live and raise their young.Beehive may also refer to:Buildings and locations:* Bee Hive, Alabama, a neighborhood in Alabama* Beehive , a wing of the New Zealand Parliament Buildings...

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

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

) and humans (honey). Output of allelopathic compounds is also liable to be reduced under such conditions – 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 and/or targeted grazing

Targeted grazing

by suitable livestock

Livestock

are also employed. While Yellow Starthistle and perhaps other species are toxic to equines, some other livestock may eat the non-spiny knapweeds with relish. In Europe

Europe

, Common Knapweed (C. nigra) and Globe Knapweed (C. macrocephala) are locally important pollen sources for honeybees in mid-late summer.

8-Hydroxyquinoline

8-Hydroxyquinoline

8-Hydroxyquinoline is an organic compound with the formula C9H7NO. It is a derivative of the heterocycle quinoline by placement of an OH group on carbon number 8...

has been identified as a main allelopathic compound produced by Diffuse Knapweed

Diffuse knapweed

(C. diffusa); native North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n plants are typically sensitive to it, while those of Eastern Europe

Eastern Europe

Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...

and Asia Minor

Asia Minor

Asia Minor is a geographical location at the westernmost protrusion of Asia, also called Anatolia, and corresponds to the western two thirds of the Asian part of Turkey...

usually have coevolved with the knapweed and are little harmed if at all, aided by native microorganism

Microorganism

A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s that break down or even feed on the abundantly secreted compound. Thus, 8-hydroxyquinoline is potentially useful to control American plants that have become invasive weeds in the Diffuse Knapweed's native range.

Arctiin, found in C. imperialis, has shown anticancer activity in laboratory studies. The roots of the long-lost C. foliosa, an endemic of Hatay Province

Hatay Province

Hatay Province is a province in southern Turkey, on the Mediterranean coast. It is bordered by Syria to the south and east and the Turkish provinces of Adana and Osmaniye to the north. The province is part of Çukurova, a geographical, economical and cultural region that covers the provinces of...

(Turkey), are used in folk medicine, and other species are presumably too. A South Italian variety of the Purple Starthistle (C. calcitrapa) is traditionally consumed by ethnic Albanians (Arbëreshë people) in the Vulture area

Vulture area

The Vulture is a geographical and historical subregion of Italy that lies in the Province of Potenza, Basilicata region.-Overview:...

(southern Italy

Italy

); e.g. in the Arbëreshë communities in Lucania

Lucania

Lucania was an ancient district of southern Italy, extending from the Tyrrhenian Sea to the Gulf of Taranto. To the north it adjoined Campania, Samnium and Apulia, and to the south it was separated by a narrow isthmus from the district of Bruttium...

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

Antioxidant

An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

activity [...] of the young whorls

Whorl (botany)

In botany, a whorl is an arrangement of sepals, petals, leaves, or branches in which all the parts are attached at the same point and surround or wrap around the stem.There are four whorls in a general flower...

of Centaurea calcitrapa, both in the DPPH

DPPH

DPPH is a common abbreviation for an organic chemical compound 2,2-diphenyl-1-picrylhydrazyl. It is a dark-colored crystalline powder composed of stable free-radical molecules...

and in the lipid peroxidation

Lipid peroxidation

Lipid peroxidation refers to the oxidative degradation of lipids. It is the process in which free radicals "steal" electrons from the lipids in cell membranes, resulting in cell damage. This process proceeds by a free radical chain reaction mechanism...

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

Xanthine oxidase

Xanthine oxidase Xanthine oxidase Xanthine oxidase (XO (sometimes 'XAO'), a form of xanthine oxidoreductase that generates reactive oxygen species. Is an enzyme that catalyzes the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid...

(XO)-inhibiting activity.

Spotted Knapweed as well as other species are rich in cnicin

Cnicin

Cnicin is a sesquiterpene lactone, esterified with a substituted acrylic acid, and belonging to the germacranolide class of natural products. It is mainly found in Cnicus , and is present in spotted knapweed plants, where highest and lowest concentrations are found in the leaves and stems...

, a bitter compound found mainly in the leaves and often used to flavor the digestif amaro

Amaro (drink)

Amaro is a variety of Italian herbal liqueur, commonly drunk as an after-dinner digestif. It is usually bitter and sweet, sometimes syrupy, usually with an alcohol content between 16% and 35%...

. In western Crete

Crete

Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...

, Greece

Greece

Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....

a local variety of C. calcitrapa called gourounaki (γουρουνάκι "little pig") also has its leaves eaten boiled by the locals. In the same island an endemic local species, C. idaea called katsoula (κατσούλα), tsita (τσίτα) or aspragatha (ασπραγκάθα), has its leaves eaten boiled by the locals too.
Some species are cultivated as ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s in garden

Garden

A garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form today is known as a residential garden, but the term garden has...

s. As regards other aspects of popular culture

Popular culture

Popular culture is the totality of ideas, perspectives, attitudes, memes, images and other phenomena that are deemed preferred per an informal consensus within the mainstream of a given culture, especially Western culture of the early to mid 20th century and the emerging global mainstream of the...

, Cornflower

Cornflower

(C. cyanus) is the floral emblem

Floral emblem

In a number of countries, plants have been chosen as symbols to represent specific geographic areas. Some countries have a country-wide floral emblem; others in addition have symbols representing subdivisions. Different processes have been used to adopt these symbols - some are conferred by...

of Östergötland

Östergötland

Östergötland, English exonym: East Gothland, is one of the traditional provinces of Sweden in the south of Sweden. It borders Småland, Västergötland, Närke, Södermanland, and the Baltic Sea. In older English literature, one might also encounter the Latinized version, Ostrogothia...

province (Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

) – where is it called blåklint, literally "blue mountain" – and of Päijänne Tavastia

Päijänne Tavastia

Päijänne Tavastia is a region in Southern Finland south of the lake Päijänne. It borders the regions Uusimaa, Tavastia Proper, Pirkanmaa, Central Finland, Southern Savonia and Kymenlaakso.- Historical provinces :...

region in Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, where it is known as ruiskaunokki ("rye

Rye

Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...

-beaks") or ruiskukka ("rye-flower"). It is also the national flower of Estonia

Estonia

Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...

– its local name rukkilill meaning "rye-lily" –, Belarus

Belarus

Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

where it is called vałoška , and one of those of Germany where it is called Kornblume ("cornflower"). The origin of the name "caltrop

Caltrop

A caltrop is an antipersonnel weapon made up of two or more sharp nails or spines arranged in such a manner that one of them always points upward from a stable base...

" 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 Roman

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

name tribulus. Lastly, the color

Color

Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

cornflower blue

Cornflower blue

Cornflower blue, a shade of azure, is a shade of light blue with relatively little green compared to blue. This color was one of the favorites of the Dutch painter Johannes Vermeer, the other being yellow....

is named after C. cyanus.

Systematics and taxonomy

As namesake member of the subtribe Centaureinae of tribe

Tribe (biology)

In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...

Cynareae

The Cynareae are a tribe of flowering plants in the daisy family Asteraceae. Most of them are commonly known as thistles; four of the best known genera are Carduus, Cynara , Cirsium, and Onopordum....

, the knapweeds are probably most closely related to genera such as Carthamus
Carthamus
The genus Carthamus , the distaff thistles, includes about 14 species of Mediterranean plants in the daisy family. The best known species is the safflower.-Species:*Carthamus arborescens L...

(distaff thistles), Cnicus
Cnicus
Cnicus benedictus , was the sole species in the genus Cnicus, but has been reclassified as Centaurea benedicta...

(Blessed Thistle), Crupina
Crupina
Crupina is a small genus of plants in the daisy family which contains only two species. The common crupina Crupina vulgaris is a notorious noxious weed on several continents. The other species, Crupina crupinastrum, also has the potential to become weedy, but it is not as bad a pest at the current...

(crupinas) or Notobasis
Notobasis
Notobasis syriaca , syn. Cirsium syriacum, Cnicus syriacus), the sole species in the genus Notobasis, is a thistle-like plant in the family Asteraceae, native to the Mediterranean region and the Middle East, from Madeira, the Canary Islands, Morocco and Portugal east to Egypt, Iran and...

(Syrian Thistle), and somewhat less closely to most other thistle

Thistle

s. The monotypic

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

Cnicus seems in fact to properly belong in Centaurea.

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

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

C. centaurium stands somewhat apart from the main lineage of knapweeds and thus the 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 lineage to avoid this problem. What seems certain however is that the basketflowers – presently treated as a section

Section (botany)

In botany, a section is a taxonomic rank below the genus, but above the species. The subgenus, if present, is higher than the section, and the rank of series, if present, is below the section. Sections are typically used to help organise very large genera, which may have hundreds of species...

Plectocephalus – 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.

Selected species

Species presently placed in Centaurea include:

Formerly placed here

Plant species placed in Centaurea in former times include:

Acroptilon repens – Russian Knapweed (as C. repens)
Cheirolophus crassifolius
Cheirolophus crassifolius
Cheirolophus crassifolius, the Maltese Centaury, Maltese Rock-centaury or Widnet il-Baħar, is a species of flowering plant in the Asteraceae family. It is endemic to Malta, where it has been the national plant of Malta since 1973. Its natural habitats are cliffs and coastal valleys...

– Maltese Rock-centaury (as C. crassifolia, C. spathulata)
Femeniasia balearica
Femeniasia balearica
Femeniasia balearica is a species of flowering plant in the family Asteraceae , and the only species in the genus Femeniasia.-Distribution and conservation:...

(as C. balearica)
Volutaria muricata (as C. muricata)

Description and ecology

Use by humans

Systematics and taxonomy

Selected species

Formerly placed here

Further reading