Centaurea jacea

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Centaurea jacea
Centaurea jacea 01.JPG
Bombus lapidarius - Centaurea jacea - Keila.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Centaurea
Species:
C. jacea
Binomial name
Centaurea jacea
L.
Synonyms
  • Centaurea vulgaris var. jacea(L.) Godr.
  • Calcitrapa jacea(L.) Peterm.
  • Jacea pratensisLam.

Centaurea jacea, brown knapweed [1] or brownray knapweed, is a species of herbaceous perennial plants in the genus Centaurea native to dry meadows and open woodland throughout Europe.

Contents

Centaurea jacea Centaurea jacea Knoopkruid.jpg
Centaurea jacea

In Britain and America, it is often found as a hybrid [2] of black knapweed, Centaurea nigra . [3] Unlike the black knapweed, the flower heads always look as if they are rayed, forming a more open star rather than a brush-like tuft.

Distribution

Brown knapweed is native to Europe, extending to West Siberia and Caucasus. It has been introduced in North America, where it is often considered an invasive species, particularly in the northeastern United States and Canada. [4]

Description

Habit

Perennial herb that grows up to 20-100 cm tall.

Stem

Single or branched, straight erect, angular and rough.

Leaves

Stem leaves gathered in a rosette, single, ovate to lanceolate, often pinnately-arched, petioled. Stem leaves sedentary, entire-edged with a tapered base.

Flowers

Collected in baskets set singly at the top of the stems, 2-6 cm wide. The basket has a perianth that is 1-2 cm long, egg-shaped. The leaves of the sheath are rounded, entire-edged, or crested, pale to brown in color. Flowers are tubular, violet-purple, occasionally white. Marginal flowers larger, fertile with a distinctly bipinnate corolla, inner flowers hermaphroditic. The stamens push the anthers upward under the touch of an insect, making it easier for them to carry pollen. Flowering occurs from June to October.

Fruits

Shiny achenes, inverted ovate, about 3 mm long. [5] [6]

References

  1. BSBI List 2007 (xls). Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-06-26. Retrieved 2014-10-17.
  2. "Centaurea x_moncktonii in Flora of North America @ efloras.org". www.efloras.org. Retrieved 24 October 2022.
  3. Rose, Francis (1981). The Wild Flower Key. Frederick Warne & Co. pp. 386–387. ISBN   0-7232-2419-6.
  4. "Centaurea jacea L. | Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2025-07-07.
  5. "MAIT - Mid-Atlantic Invaders Tool".
  6. "Centaurea jacea (brown knapweed): Go Botany". gobotany.nativeplanttrust.org. Retrieved 2025-07-07.