GROWTH HABIT: Rigid branching, annual, 2 to 3 feet tall.
LEAVES: Basal leaves are deeply lobed while upper leaves are entire and sharply pointed.
STEMS: Winged stems covered with a cottony pubescence.
FLOWER: Yellow, located singly on ends of branches, and armed with sharp straw-colored thorns up to 3/4 inch long.
SEEDS: Fruits from ray flowers are dark-colored without bristles, while fruits from disk flowers are lighter and have a tuft of white bristles.
OTHER: Introduced from Europe, grows on various soil types and is usually introduced on roadsides and waste areas. "Chewing disease" results when horses are forced to eat the yellow starthistle.