Centaurea jacea Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
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
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.
In Greek κενταυριν
(kentaurin) means Knapweed the standard common name of many
As for the name
it is likely coming from
(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.
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.
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,
- From 20 to 48 inches tall.
- Branching openly near the top.
- Ridged and sometimes purple-striped.
- Becoming progressively smaller up the stem, the larger ones
possibly with few lobes.
- The basal leaves up to 6 inches long,
tapering at both ends.
- The cauline leaves
- In few-headed corymbiform arrays.
- Rose to purple, rarely white.
- With up to 100 tubular disk florets,
the sterile ones more or less expanded and exceeding the
corollas of the fertile ones.
- Without ray florets.
- With somewhat hairy phyllaries,
wider at the tips, with broad, thin, papery, fringed
margins, with a dark brown center,
with the tips overlapping the base of nearby phyllaries.
- Blooming from the end of July to October in my area,
25 km north of Montréal.
- A small cypsela,
between 2.5 and 3 mm.
- Tan, finely hairy, without pappus.
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.
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.
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
The photos of the gallery were taken either with one of the following:
The title in the window shows the date when the picture was taken,
i.e. jan_30_06... would mean that the photo was taken on the 30th of
January, the 06 is for the 6th picture taken that day.
- Minolta DiMAGE 7.
- Canon PowerShot A530
- Canon Xt Rebel, usually with the EF-S60mm f/2.8 Macro USM objective.
- EPSON Perfection 1650 (scanner).
The month, day and picture number might be followed by a letter:
- c for the Canon Xt Rebel.
- a for the Canon A530.
- m for the Minolta DiMAGE 7.
- s for the EPSON scanner.
Click on the thumbnails to get larger view.
The original photos are usually in TIFF format,
the photos shown are generally in JPEG format,
usually of dimensions one half (surface one quarter)
for loading time reduction.
The leaves were scanned at 300 dpi,
this allows to measure the dimensions of the leaves.