Common Names in English:
Bachelors Button, Cornflower
The largest family of flowering plants , the Compositae (Asteraceae), comprising about 1,100 genera and more than 20,000 species and characterized by many small flowers arranged in a head looking like a single flower and subtended by an involucre of bracts. A head may consist of both ray flowers and disk flowers, as in the sunflower, of disk flowers only, as in the burdock, or of ray flowers only, as in the dandelion.
, biennials, or perennials, 20-300 cm, glabrous
. Stems erect
, or spreading
or branched. Leaves basal and cauline; petiolate
or sessile; proximal
often ± deeply lobed
in C. benedicta ), distal ± smaller, often entire, faces
glabrous or ± tomentose, sometimes also villous
, or puberulent
, often glandular-punctate. Heads discoid
, or radiant, borne singly or in corymbiform
arrays. Involucres cylindric
. Phyllaries many in 6-many series, unequal, proximal part appressed
, body margins entire. distal parts expanded into erect to spreading, usually ± dentate
, spine. tipped or spineless. Receptacles flat, epaleate, bristly
. Florets 10-many; outer usually sterile
, corollas slender and inconspicuous to much expanded, ± bilateral
; inner fertile
, corollas white to blue, pink, purple, or yellow, bilateral or radial
, often bent at junction of tubes
linear-oblong, acute; anther
, apical appendages oblong
; style branches: fused portions with minutely hairy
portions minute. Cypselae ± barrel-shaped, ± compressed
, apices entire (denticulate
benedicta ), glabrous or with fine, 1-celled hairs
, attachment scar
(with or without elaiosomes) ; pappi 0 or ± persistent
, of 1-3 series of smooth or minutely barbed
, stiff bristles
or narrow scales
. x = 8, 9, 10, 11, 12, 13, 15.
Species ca. 500: introduced ; Eurasia , n Africa, widely introduced worldwide.
Taxonomic limits of Centaurea have been controversial. The genus has great morphologic diversity , and studies have revealed much cytologic (e.g. , N. Garcia-Jacas et al. 1996) and palynologic (e.g., G. Wagenitz 1955) variation as well. During the nineteenth and twentieth centuries, various taxonomists attempted, with limited success, to divide Centaurea into smaller genera or workable infrageneric taxa. The relations of several satellite genera have been controversial as well.
Recent molecular phylogenetic studies (A. Susanna et al. 1995; N. Garcia-Jacas et al. 2000, 2001) have begun to clarify relationships within Centaurea and between Centaurea and other genera. These studies make it clear that Centaurea as traditionally defined is polyphyletic, and that generic boundaries should be realigned if monophyletic taxa are to be recognized. Some taxa traditionally included within Centaurea (e.g., the two native North American species, Centaurea americana and C. rothrockii) fall outside the redefined generic boundaries and are here treated in Plectocephalus. Others usually placed into segregate genera (e.g., Cnicus benedictus) are firmly nested within Centaurea. Because the type species of Centaurea (C. centaurium Linnaeus, an African species) falls outside the main lineage of the genus, a proposal has been made to conserve Centaurea with a different type species (W. Greuter et al. 2001), thereby maintaining the nomenclatural stability of most of the numerous species that do fall within the principal Centaurea clade.
Although several Centaurea species are widely established as members of the North American flora , and some of these are widely distributed invasive weeds , some of the taxa listed by J. T. Kartesz and C. A. Meacham (1999) are apparently waifs and not permanent members of the flora. These taxa are discussed informally immediately below.
Although Cnicus has usually been recognized as a distinctive monotypic genus, it has been merged into Centaurea by various authors (e.g., K . Bremer 1994; G. Wagenitz and F. H. Hellwig 1996) . Recent molecular systematic studies (N. Garcia-Jacas et al. 2000) provide additional evidence that it is nested within Centaurea.
Flowers: Bloom Period: June, July, August. • Flower Color: lavender, mauve , medium blue, near white, pink, rose, violet, white
Size: 12-18" tall.
Culture: Space 9-12" apart.
Soil: Minimum pH: 6.1 • Maximum pH: 7.8
Sunlight: Sun Exposure: Full Sun .
- Whittaker & Margulis,1978
- Haeckel, 1866
- Cavalier-Smith, 1981
- Sinnott, 1935 ex Cavalier-Smith, 1998
- Vascular Plants
- Brongniart, 1843
- Takhtajan, 1967
- Takhtajan Ex Reveal, 1992
- Lindley, 1833
- Giseke, 1792, nom. cons., nom. alt.
- C. Linnaeus, 1753
- Knapweed, star thistle, cornflower [Greek kentaurieon, ancient plant name associated with Chiron, a centaur famous for knowledge of medicinal plants]
- Specific epithet:
Polka Dot Mix
- Botanical name: - Centaurea cyanus 'Polka Dot Mix' Linnaeus
- Cultivar: Polka Dot Mix
- Specific epithet: cyanus - Linnaeus
- Genus: Centaurea () - C. Linnaeus, 1753 - Knapweed, star thistle, cornflower [Greek kentaurieon, ancient plant name associated with Chiron, a centaur famous for knowledge of medicinal plants]
- Subtribe: Centaureinae ()
- Tribe: Cardueae ()
- Subfamily: Carduoideae ()
- Family: Compositae () - Giseke, 1792, nom. cons., nom. alt.
- Order: Asterales () - Lindley, 1833
- Superorder: Campanulanae () - Takhtajan Ex Reveal, 1992
- Subclass: Asteridae () - Takhtajan, 1967
- Class: Spermatopsida () - Brongniart, 1843
- Subphylum: Euphyllophytina ()
- Phylum: Tracheophyta () - Sinnott, 1935 ex Cavalier-Smith, 1998 - Vascular Plants
- Subkingdom: Viridaeplantae () - Cavalier-Smith, 1981
- Kingdom: Plantae () - Haeckel, 1866 - Plants
Members of the genus Centaurea
ZipcodeZoo has pages for 82 species, subspecies, varieties, forms, and cultivars in this genus:
C. akamantis (Akamas Centaury) · C. alpestris (Greater Centaury) · C. americana (American Basketflower) · C. americana 'Aloha' (American Knapweed) · C. americana 'Jolly Joker' (American Knapweed) · C. aspera (Rough Star-Thistle) · C. atropurpurea (Centaurea) · C. bella (Knapweed) · C. benoistii (Maroon Cornflower) · C. biebersteinii (Ballast Waif Centaurea Biebersteinii) · C. bovina (Pasture Knapweed) · C. cachinalensis (Flor Del Minero) · C. calcitrapa (Big-Head Purple Starthistle) · C. calcitrapoides (Smallhead Star-Thistle) · C. cineraria (Dusty Miller) · C. cineraria 'Colchester White' (Dusty Miller) · C. crupina (Crupina) · C. cyanoides 'Blue Carpet' (Cornflower) · C. cyanus (Bachelor's Button) · C. cyanus nana 'Jubilee Gem' (Bachelors Button) · C. cyanus 'Black Ball' (Bachelors Button) · C. cyanus 'Black Boy' (Bachelors Button) · C. cyanus 'Black Gem' (Bachelors Button) · C. cyanus 'Black Magic' (Bachelors Button) · C. cyanus 'Blue Boy' (Bachelors Button) · C. cyanus 'Blue Diadem' (Bachelors Button) · C. cyanus 'Classic Blue' (Bachelors Button) · C. cyanus 'Dwarf Blue Midget' (Bachelors Button) · C. cyanus 'Frosted Queen Mix' (Bachelors Button) · C. cyanus 'Frosty Mix' (Bachelors Button) · C. cyanus 'Mauve Queen' (Bachelors Button) · C. cyanus 'Polka Dot Mix' (Bachelors Button) · C. dealbata (Knapweed Centaurea Dealbata) · C. dealbata 'Rosea' (Knapweed) · C. debeauxii (Meadow Knapweed) · C. debeauxii thuillieri (Meadow Knapweed) · C. debeauxii subsp. thuillieri (Meadow Knapweed) · C. depressa (Centaurea) · C. diffusa (Diffuse Knapweed) · C. diluta (North African Knapweed) · C. eriophora (Sand-Heath) · C. gymnocarpa (Velvet Centaurea) · C. hypoleuca DC. 'John Coutts' (Knapweed) · C. iberica (Iberian Knapweed) · C. jacea (Brown Knapweed) · C. jacea x nigra (Hybrid Knapweed Centaurea Jacea X Nigra) · C. macrocephala (Armenian Basketflower) · C. melitensis (Cockspur Thistle) · C. moncktonii (Meadow Knapweed) · C. montana (Mountain Bluet) · C. montana 'Alba' (Mountain Bluet) · C. montana 'Amethyst in Snow' (Mountain Bluet) · C. montana 'Dot Purple' (Mountain Bluet) · C. montana 'Gold Bullion' (Batchelor's Button) · C. moschata 'Dairy Maid' (Sweet Sultan) · C. moschata 'Imperialis' (Sweet Sultan) · C. moschata 'The Bride' (Sweet Sultan) · C. nigra (Black Knapweed) · C. nigrescens (Short-Fringe Starthistle) · C. orientalis (Centaurea) · C. ovina (Lilac Knapweed) · C. paniculata (Jersey Knapweed) · C. phrygia (Scandinavian Starthistle) · C. pindicola (Centaurea) · C. pulcherrima (Pink Bachelors Button) · C. 'Pulchra Major' (Bachelor's Button) · C. ragusina (Dubrovacka Zecina) · C. rothrockii (Basket Flower) · C. scabiosa (Great Starthistle) · C. solstitialis (Barnaby Star-Thistle) · C. solstitialis solstitialis (St. Barnaby's Thistle) · C. stoebe (Spotted Knapweed) · C. sulphurea (Sicilian Starthistle) · C. thuillieri (Meadow Knapweed) · C. transalpina (Alpine Knapweed) · C. trichocephala (Feather-Head Knapweed) · C. triumfetti (Squarrose Knapweed Centaurea Triumfetti) · C. triumfettii (Spreading Thistle) · C. uniflora (Single-Flower Knapweed) · C. uniflora nervosa (Singleflower Knapweed) · C. xpratensis (Meadow Knapweed) · C.'Nigra' (Bachelor Buttons)
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- Garcia-Jacas, N., A. Susanna, V. Mozaffarian, and R. Ilarslan. 2000. The natural delimitation of Centaurea (Asteraceae: Cardueae): ITS sequence analysis of the Centaurea jacea group. Pl. Syst. Evol. 223: 185199.
- Moore, R. J. 1972. Distribution of native and introduced knapweeds (Centaurea) in Canada and the United States. Rhodora 74: 331346.
- Roché, B. F. and C. T. Roché. 1991. Identification, introduction, distribution, ecology, and economics of Centaurea species. In: L. F. James et al., eds. 1991. Noxious Range Weeds. Boulder, San Francisco, and Oxford. Pp. 274291.
- Wagenitz, G. 1955. Pollenmorphologie und Systematik in der Gattung Centaurea L. s.l. Flora 142: 213279.
- Brands, S.J. (comp.) 1989-present. The Taxonomicon. Universal Taxonomic Services, Zwaag, The Netherlands. Accessed March 27, 2012.
- Zipcode Zoo Species Identifier: 951722
- David J. Keil, Jörg Ochsmann "Centaurea". in Flora of North America Vol. 19, 20 and 21 Page 52, 57, 58, 67, 83, 84, 96, 171, 172, 176, 177, EFloras.org. [back]