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Noxious Weeds


Yellow starthistle (Centaurea solstitalis L.)

Sunflower family (Asteraceae) 

Photo collage of Yellow starthistle 

GROWTH HABIT:
Yellow starthistle, a native European annual, is grayish green and grows 1 to 3 feet (30 to 90 cm) tall. The rigid stems are spreading and branched from the base. They are covered with white to gray, loose, cottony wool.
LEAVES: 
There are three types of leaves. The basal leaves are 2 to 3 inches (5 to 7.5 cm) long and deeply lobed. The leaves on the stem are alternately arranged. The lower areas are narrow, with blades that extend down the stem forming wings. The upper leaves are short, 1/2 to 1 inch (1.25 to 2.5 cm) long, narrow, and sharply pointed.   Their cottony pubescence gives them a white to gray green color.
FLOWERS:
The dandelion-like, bright yellow flower heads occur singly at the ends of the branches. They are about 1 inch (2.5 cm) across with long, sharp, rigid, 3/4 inch (2 cm), straw-colored, spines at the base. The lower spines have three prongs, while the middle and upper ones are unbranched
SEEDS:There are two types of seed; some are light colored with white bristles, while others are dark to black without bristles
OTHER:
Yellow starthistle infests cultivated fields, pastures, and waste lands in California, Oregon, Washington and Idaho. “Chewing disease,” a nervous disorder, occurs in horses forced to eat yellow starthistle. This may occur during poor, dry years. They end up not being able to eat and starving to death.
KEY CHARACTERS:
  • The seedlinghas oblong, somewhat tongue-shaped seed leaves (cotyledons). The first true leaves are somewhat longer and dull green compared to the whitish gray leaves of later growth. The leaves are slightly rough textured.
Distribution:
Previously treated sites - in the Owens Valley, Inyo County.