Santa Barbara County
Weed Management Area


Weed Alert!

click to view bigger picturePurple Starthistle
Asteraceae: Centaurea calcitrapa
CDFA B rated; CalEPPC B rated
Purple starthistle is a vicious, spiny plant with a bitter taste, that cattle, horses and wildlife avoid grazing. The species name, "calcitrapa", is derived from the word caltrop, a weapon used to hinder the movement of tanks and calvary in ancient and modern times.
In Santa Barbara County, it can be found as a rangeland pest from Las Cruces to Lompoc. It has been recorded near Santa Maria and Summerland and was found in Los Alamos in the early 1950s.
Purple starthistle is biennial thistle, but may be an annual or short-lived perennial under some conditions. It has a mounding growth habit with purple flower heads with sharp, stiff spines. The plant can break at ground level, dispersing the seeds much like a tumbleweed.
Small infestations can be controlled by grubbing or digging -- cutting the plant, two inches below the soil surface, early in the growing season. Clopyralid, glyphosate, 2,4-D and dicamba have been effective in controlling this weed. Mowing is not effective.
For more information, on the web, visit: and
Bossard, Carla C. ed., et al. Invasive Plants of California's Wildlands. 2000. University of California Press
CDFA's Encycloweedia.

*** This is a notice of a noxious weed of concern that occurs in Santa Barbara County. Remember - pesticides must be used in a manner consistent with the label directions. Permits may be required to use pesticides in agricultural areas and/or to conduct work in riparian areas.



October 4, 2002