Weed ID

YELLOW STARTHISTLE

Asteraceae or Sunflower Family
Centaurea solstitialis

GROWTH HABIT: Winter annual, grows 2 to 3 feet tall.

LEAVES: Basal leaves are deeply lobed while upper leaves are entire and sharply pointed. Stem leaves are entire, linear, and have thin woolly hairs that persist through the growing season.

STEMS: Rigid branching, winged stems covered with a cottony pubescence. Stems range from 1 to 5 feet tall.

FLOWERS: Flower heads are yellow, located singly on ends of branches, and armed with sharp straw-colored thorns up to 3/4 inches long.

ROOTS: Deep penetrating roots.

SEEDS: Two types: dark-colored without bristles or light-colored with a tuft of white bristles at the end. A single plant can produce up to 150,000 seeds. Ten percent of the seeds are viable up to 10 years.

REPRODUCES: By seed.

HABITAT: Grows in various soil types and is usually introduced on roadsides and waste areas.

"This weed causes Chewing Disease when horses eat it"