Centaurea jacea Linnaeus

Remark The words or terms in red (actually dark orange) in the text are defined in a glossary.


oct_05_02c.gthmb can't be loaded. Centaurea jacea is an introduced and naturalized perennial plant of North America that is native to Europe and to western temperate Asia (Lebanon, Syria, Turkey). It is considered a noxious weed in North America. It has a woody root crown, is between one and three feet high, branching near the top, and has magenta to pink flower heads that measure 1 to 1.5 inch across. The plants have a chromosome number (2n) of 22 or 44.

Centaurea jacea has been the subject of much controversy. The plants are widely and variable in readily noticeable characters of the heads, florets and cypselae. In Europe particularly, several entities are commonly recognized, usually at the species level. The various named taxa are apparently all more or less interfertile, and natural hybridization has resulted in a plethora of intermediates that variously combine the features of the parental types. North American botanists have usually recognized three species within the Centaurea jacea complex: Centaurea jacea, Centaurea nigra, Centaurea nigrescens, (under several different names), and Centaurea × pratensis, the last a collective for the various intermediates between Centaurea jacea and Centaurea nigra.

Name

In Greek κενταυριν (kentaurin) means Knapweed the standard common name of many Centaurea species. As for the name κενταυριν it is likely coming from κενταυροσ (kentauros) that means centaur. One of the famous centaur was Chiron, known for his exceptional goodness and wisdom and for his knowledge of medicinal plants. He raised Asclepius, a god of healing and taught him medicine which Asclepius went on to perfect. Since some species of Centaurea have been used as medicinal herbs, the genus name might come from the association of Chiron, centaur, to Centaurea. For an other origin of the name, some sources say that Chiron used the flower of some Centaurea species to heal wounds, including his own, after battle.

As for the jacea epithet it is in fact the old generic name. A common French vernacular name for some Centaurea species is Jacée.

Common names

Some of the vernacular names of Centaurea jacea are: Brown Knapweed, Rayed Knapweed, Brown-ray Knapweed, Brown Centaury, Horse-Knobs, Hardheads. Some of the French vernacular names are Centaurée jacée, Jacée, Jacée des pré and Tête de moineau.

Identification

The scale-like bracts, with broad, thin, papery, fringed margins, with a dark brown center, beneath the flowers are a good clue in identifying the Centaurea genus. But Centaurea jacea is differentiated form the other species by its bracts that are without comblike fringe and that have a brown, papery, translucent tip. draw.jpg can't be loaded.

Description

Stems

Leaves

Flower heads

Fruits

Habitat

Centaurea jacea grows in grasslands and in open woods over most of Europe or Eurasia and occurs at elevations up to 6,600 feet in mountainous areas of central Europe to 63° 43' north latitude. In Russia, it grows in meadows, woodland clearings, and in cutover areas of forest. The species can tolerate partial shade. In Romania, it grows in pastures, orchards, and plains, but it prefers the mountainous regions.

In North America Centaurea jacea prefers moist, cooler conditions than other Centaurea. It can be found growing in grasslands, open woods, meadows, pastures, woodland clearings, and in cutover areas of forest.

Distribution

map_na.jpg can't be loaded. Centaurea jacea, an introduced species in North America, can be found in many USA States and Canadian provinces, as shown on the map. It is even found in Groenland, and is a common Eurasian plant.

Notes

As several other Centaurea species, Centaurea jacea has shown itself to be aggressive and invasive. It is particularly so in meadows and pastures, crowding out more desirable forage. It is capable of forming large infestations under favorable conditions.

Centaurea jacea has been grown both as an ornamental garden plant and as a crop. It has been suggested as a potential bioindicator for tropospheric ozone.

Gallery

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The month, day and picture number might be followed by a letter:

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Plants

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Leaves

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Flower heads

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