Centaurea jacea

Species category

Weed

Common name

brownray knapweed

Diagnostic characters

Planting unit

AcheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.

Shape

ObovateObovate:
Inverted egg shaped with apical end the broadest.

Size

  • Length: 3 mm
  • Width: 1.5 mm
  • Thickness: 1 mm

Color

Light brown with four yellow longitudinal ribs

Texture

Four strong longitudinal ribs; surface covered with long waves.

Other structures

Collar with no pappusPappus:
Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 
; lateral scar.

Identification notes

AcheneAchene:
A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.
surface covered with longitudinal wavy lines. PappusPappus:
Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 
none. Scar lateral, near the base.

Noxious weed seed categories

State Noxious Weed: Arizona, California, Washington

AOSA examination list

Not included

Nomenclature

Family

Asteraceae

Valid name

Centaurea jacea L.

 Centaurea jacea.  Achenes are covered with long waves. 
Centaurea jacea. Achenes are covered with long waves.