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Centaurea melitensis

Species category

Weed

Common name

Maltese star-thistle

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

Oblong

Size

  • Length: 3 mm
  • Width: 1 mm
  • Thickness: 0.5 mm

Color

Light brown; yellow longitudinal lines, collar and base.

Texture

Smooth

Other structures

PappusPappus:
Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 
 is white and delicate. Scar notch is lateral and hook-like.

Identification notes

PappusPappus:
Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 
 bristles of various lengths with the longest being about 4 mm. Scar notch very deep, lateral to the base; basalBasal:
The base of the fruit or seed opposite the apical end.
 tissue extends up around the scar forming a hook-like appearance.

Noxious weed seed categories

State Noxious Weed: Arizona, California, Nevada, Oregon, Utah

AOSA examination list

Not included

Nomenclature

Family

Asteraceae

Valid name

Centaurea melitensis L.

Centaurea melitensis. Achenes with a scar notch that is lateral and hook-like.
Centaurea melitensis. Achenes with a scar notch that is lateral and hook-like.
Centaurea melitensis. Looking into the center of the outer pappus whorls to see the innermost whorl covering the stylar remains. Photo courtesy of USDA-APHIS-PPQ.
Centaurea melitensis. Looking into the center of the outer pappus whorls to see the innermost whorl covering the stylar remains. Photo courtesy of USDA-APHIS-PPQ.