Invasive Plant Guide: Italian Thistle


Carduus pycnocephalus

Hand pulling Italian thistle

Identifying characteristics

  • Flower color: pink-purple
  • Flowers: May to July
  • Stems: partly winged; spiny.  Multiple flower-heads at end of stems.
  • Plant height: ranges from about 1 foot to 6 feet
  • Leaves: very spiny, lobed, wooly hairs underneath smooth on top
  • Seeds: small with a downy pappus which assists in wind dispersal
  • Growth habit: annual


Open disturbed sites, roadsides, fields, pastures, hillsides, rangeland, forest openings. Prefers warm, dry climate areas.  Tolerates a wide range of soil types.

Italian thistle is not common in the Mid Klamath.  It is present in Weitchpec, isolated sites along the highway between Happy Camp and Somes Bar, and on a forest road near the headwaters of Rock Creek.  There is also a population in Forks of Salmon.



Plant spreads by seed only. Seeds are viable for up to seven years, and germinate aggressively. 

More Info

California Department of Food & Agriculture