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yellow thistle

Scientific Name: Cirsium horridulum

Family: Asteraceae

Category: Dicot

Growth: Forb/herb

Duration: Annual, Biennial

Other Names: CT (yellow thistle), NH (yellow thistle), PA (horr

       

Yellow Starthistle (Centaurea solstitialis)

Yellow starthistle, scientifically known as Centaurea solstitialis, is also recognized by several common names, including golden star thistle, St. Barnaby's thistle, yellow centaury, and yellow cockspur.

Considerations for Pets

  • The text mentions the plant's seedheads "hitchhiking by jabbing spines," and mature plants having "large thorns under them." These physical attributes could pose a hazard to animals.
  • The text mentions that Yellow Thistle is considered "toxic" to livestock.

Considerations for Children

  • The text mentions the plant's seedheads "hitchhiking by jabbing spines," and mature plants having "large thorns under them." These physical attributes could pose a hazard to children.

Taxonomy and Nomenclature

  • Scientific Name: Centaurea solstitialis
  • Family: Asteraceae (also referred to as N.O. Composite)
  • Synonyms: St. Barnaby's Thistle

Distribution and Habitat

  • Native to the Mediterranean Basin region, encompassing Africa, temperate Asia, and Eurasia, including the Balkan-Asia Minor region, the Middle East, and south-central Europe.
  • Introduced to western U.S. ports as a seed contaminant in imported alfalfa seed.
  • Frequently found in disturbed areas such as roadsides, abandoned fields, and waste areas.

Ecological Role

  • Classified as an invasive, exotic, seedy herbaceous annual.
  • Known for being highly competitive, often forming impenetrable stands that outcompete other vegetation.
  • Considered a problematic weed in areas like Yosemite National Park and a new invader in Montana.

Morphological Characteristics

  • A long-lived winter annual, occasionally biennial.
  • Grows to a height of 0.25-3 ft (0.07-0.9 m).
  • Leaves near the base are petiolate and dissected, measuring 2-6 inches.
  • Mature plants are recognized by yellow flowers with large thorns under them.
  • Young plants appear silvery-green, transitioning to gray-green later in the season.

Interactions with Other Organisms

  • Flowers provide nectar for honey bees.
  • The Yellow Starthistle Hairy Weevil (Eustenopus villosus) feeds on the flowers as an adult, and its larvae feed internally, representing a potential biocontrol agent.

Additional Information

  • Seeds can remain dormant for as long as 10 years.

Resources

  • University of California guidelines for control of Yellow Starthistle.
  • Center for Invasive Species and Ecosystem Health.
  • UC IPM Pest Management Guidelines: Yellow Starthistle