Javascript is required to view this site. Skip to main content
Text:    -   | Translate

Purple Starthistle


Centaurea calcitrapa - Asteraceae Family

purple_starthistle_1_tile   purple_starthistle_2_tile  purple_starthistle_3_tile  purple_starthistle_4_tile


  • Flowers: The flowers are purple and 0.6 to 1 inches in diameter. Twenty-five to 40 florets (small flowers) make up each flower head. Underneath the flower are spine-tipped bracts that are greenish or straw-colored.
  • Seeds: The seeds are oblong and 2.5-3.5 mm long. They are white and often streaked with brown.
  • Leaves: The leaves are alternate, with deeply divided lower leaves and narrow and undivided upper leaves. The leaves are five to eight inches long and have dots of resin on their surfaces.
  • Flowering Time:  The plant produces long stems in spring and early summer. It flowers from June through November.
  • Life cycle:  Purple Starthistle can live as an annual in extremely favorable conditions, but most often lives as a biennial. 


  • Purple Starthistle can quickly displace native flora in disturbed areas due to its rapid growth and seed production. 
  • Purple Starthistle is unpalatable to grazing animals and rapidly degrades the forage quality in any infested areas.
  • With thicker and stronger spines than its relatives, Purple Starthistle poses a threat of injury to both humans and animals moving through infested areas.


Most effective control methods

  • Small infestations of Purple Starthistle can be effectively controlled by manually pulling and disposing of plant remains. Plants should be cut at least 2 inches below the surface.
  • There are no effective biocontrol agents currently approved for use in the US to control Purple Starthistle.
  • Chemical control can prove effective on Purple Starthistle if applied in early spring. Multiple treatments may be needed for best control. 


Large Images


Barry Rice,,

Purple starthistle: flower



Steve Dewey, Utah State University,

Purple starthistle: rosette



K. Mosbruger, Salt Lake County Weed Control Program

Purple starthistle: flower and foliage



Barry Rice,,

Purple starthistle: sharp spines



K. Mosbruger, Salt Lake County Weed Control Program

Purple starthistle: infestation



Barry Rice,,

Purple starthistle



Barry Rice,,

Purple starthistle: flowers, spines, and foliage


  • Purple Starthistle Fact Sheet

  • References

    California Invasive Plant Council. IPCW plant report: Centaurea calcitrapa. Retrieved from

    DiTomaso, J.M., G.B. Kyser et al. (2013). Weed Control in Natural Areas in the Western United States [PDF file]. Weed Research and Information Center, University of California. Retrieved from View PDF

    Graham, J. & Johnson, W. Managing purple and Iberian starthistles [PDF file]. Retrieved from View PDF

    Marin Agricultural Land Trust. (2012, April). Purple star-thistle control [PDF file]. Retrieved from View PDF

    Reeves, K. (2010). Exotic species: purple starthistle. Retrieved from

    Texas Invasive Species Institute. (2014). Purple star thistle. Retrieved from