Species category

Weed

Common name

yellow star-thistle

Diagnostic characters

Identification notes

AchenesAchene:
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.
oblong to obovateObovate:
Inverted egg shaped with apical end the broadest.
, compressed; color solid black to yellow with intermediate mixtures of black blotches on a yellow background. AchenesAchene:
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.
with or without pappusPappus:
Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 
, which is usually associated with lighter achenesAchene:
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.
. Shoulders at apexApical:
The distal end of the fruit or seed away from the point of attachment or attachment scar.
squared or rounded. Scar in lateral depression near base.

Noxious weed seed categories

State Noxious Weed: Arizona, California, Colorado, Hawaii, Idaho, Missouri, Montana, Nevada, North Dakota, Oregon, Utah, Washington, Wyoming 

AOSA examination list

Included

More information

For more information, see ISMA fact sheet.

Nomenclature